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Nov 11, 2025 ERCOT RTC + B ERCOT’s transition from Operating Reserve Demand Curve (ORDC) scarcity pricing to the new RTC+B framework marks a fundamental shift in how batteries and other resources will earn value in Texas’ evolving ancillary services market. ERCOT’s ORDC scarcity pricing is being replaced with a more balanced, data-driven framework. TB-2 valuations have been trending over the last 6-9 months. The composite TB-2 is up by more than 20% (7-year term, Q1 2027 PIS) According to E3, after the passage of the Budget Reconciliation Bill, the phase out of tax credits for solar and wind result in lower deployments and a roughly $15/MWh increase in average annual energy prices from 2026 to 2035. RTC-B is going to be implemented by the end of the year by retiring ORDC scarcity adder. This means that asset owners must prepare for lower ancillary service revenues, higher arbitrage shared, and upside tied to scarcity frequency post implementation This also required four (4) new telemetry points: Frequency Responsive Capacity High Limit (HFRL in MW) High limit of the resources’ capacity that is frequency responsive Frequency Responsive Capacity Low Limit (LFRL in MW) Frequency Responsive Capacity Factor (FRQF) Maximum amount of total base point provided by the frequency responsive capacity of the resource Inactive Power Augmentation Capacity (PAUG in MW) Power augmentation capacity that is not on-line in HSL. This is used in SCED to determine the portion of the non-spin award that will be provided by power augmentation capacity that is not active and deployed as offline non-spin The new telemetry points are intended to inform Security Constraint Economic Dispatch (SCED) the Frequency Responsive Capacity of the resource to ensure that the Regulation and RRS-PFR awards are within the frequency responsive capacity. There are no frequency responsive capacity limitations when providing Non-Spin and ECRS The new demand curve will increase the ancillary service prices under scarcity conditions; however, we note that the scarcity adder will kick in first for RRS and ECRS before RegUp Currently, the onus is on the QSEs to ensure that Regulation and/or RRS-PFR are not coming from the steamer capacity and preserve sufficient headroom on GTs. ERCOT also enforces real-time and post-hoc compliance checks. The improved telemetry will eliminate this burden on QSEs and ERCOT. In practice, the optimization process ensures that resources are not incentivized by prices to deviate from their awards, i.e., a BESS will receive the same operating profit it would have received from the energy market, making it indifferent to the scheduling of its capacity for energy or ancillaries. For ERCOT Contingency Reserve Service (ECRS) it states that batteries can only qualify to provide a quantity that they can sustain for two consecutive hours. Essentially, a two-hour battery can qualify for up to 100% of its rated power as ECRS in any interval. However, a one-hour battery would only be eligible to provide up to 50% of its rated power as ECRS. However, this is changing…ECRS is transitioning from a 2-hour requirement to a 1-hour requirement. RRS and Regulation are being reduced from 1 hour to 30 minutes. Non-spin remains at 4 hours. Since most batteries in ERCOT are at least one hour in duration, the change in duration requirements for RRS and Regulation has minimal bearing on how much capacity is eligible to qualify to provide each of these services. However, the shift to a 1-hour requirement results in a 29% increase in eligible battery capacity for ECRS. This is because RTC+B shifts ECRS to a 1-hour requirement. A 100 MW / 120 MWh battery that was limited to 60 MW under the 2-hour rule can now offer its full 100 MW. It isn’t actually clear how revenues will be impacted as RTC procures ancillaries in real time. However, according to Modo Energy, using Day-Ahead prices as a proxy, batteries would earn about 14% less (or ~ $66 per MW less) under RTC+B on this high-priced day with this operational profile, assuming all RTC+B awards were made exclusively in the Real-Time Market. The reduced revenues reflect limits from SoC checks and the inability to capture extreme Non-Spin pricing. As ERCOT phases out ORDC scarcity pricing and implements RTC+B, asset owners and operators should expect a new balance of risks and opportunities—reduced reliance on scarcity adders, more precise telemetry requirements, evolving duration thresholds, and real-time procurement dynamics that reshape revenue profiles. While uncertainty remains around long-term impacts, it’s clear that operational flexibility, accurate dispatch data, and strategic bidding will play a larger role than ever in capturing value. Raafe Khan, Shawn Shaw < Back Back

Aug 23, 2024 Solar Availability Series Part 2 Welcome back for Part 2 of Camelot’s series on solar availability, which is an appropriately hot topic as the industry continues to mature. If you’re just joining us for the series, Part 1 can be found here , and it includes some background on the current state of industry assumptions. Today we’ll cover the not-so-simple task of calculating and reporting downtime, along with some implications. Subsequent parts will describe ways of maximizing availabilities and Camelot’s official stance as an IE. Thank you for joining us! Introduction As expressed in Part 1 , availability is a way of quantifying lost generation potential due to outages; it measures whether a component or system is operating when it ought to be. An availability of 100% at any given time means everything is operating when it should, whereas an availability of 0% means the entire component or system is offline. The plot below illustrates a case where the entire site stopped producing power and was restored the following day. There will be more on this figure later. SCADA Data Collected at a Utility-Scale Solar Project Over Two Summer Days To better summarize the operations at a project based on high-resolution data collected at a site, production and availability data are typically aggregated and reported into monthly operating reports (MORs) which are shared with key stakeholders on a project. Monthly numbers are also aggregated into quarterly and annual reports. Because there is typically some seasonal variation in downtime, most folks will refer to annual availability numbers when benchmarking against expectations, and so when we talk about availability assumptions, we are referring to annual averages . A Deeper Dive Into Metrics The simplest but less useful measure of availability is time-based. It’s calculated as Uptime/(Uptime+Downtime) , so it only considers the time it takes to bring the system back online over the period. However, the most useful measure of availability in most contexts is energy-based . It uses an estimate of the energy lost during the period, and is calculated as Actual Production/(Actual Production+Lost Production) . We care more about lost production than anything; when building out a financial model, we multiply pre-downtime production by the assumed availability to arrive at post-downtime production, so we want to use energy-based availability if possible. This is often why, despite PVSYST’s ability to model downtime, the loss factor is most commonly applied outside of PVSYST; the software interprets the loss as time-based and will apply random downtime throughout the modeled year, resulting in an unintended energy-based loss. Time-based availabilities are not well suited for financial modeling, and we recommend time-based metrics only be used if they are defined and used in O&M contracts, as we’ll touch on below. How are uptime, downtime, actual production, and lost production determined? Uptime and downtime are relatively easily defined on a site-level. SCADA systems will typically flag periods when the site or major components are down, and the duration of these events will sum to be the downtime for the site. In cases when a portion of the site is offline, uptime is often weighted by the portion of the affected site (ideally on a production-potential basis). Actual production comes directly from the power meter, typically at the point of interconnect (POI). Calculating lost production usually involves several steps which are all built into the software used to log and report operational data: Determine “expected production” for each timestep based on the energy model for the site and the existing, measured site conditions (eg irradiance). The model should be validated as an accurate representation of the relationship between measured inputs and production. Referring to the plot above, expected production is the red line, which is based primarily on the plane-of-array irradiance (green line). Calculate the energy lost for each timestep, which is represented by the “Δ” in the plot above. Sum energy lost at each timestep across the entire reporting period. The same calculations hold for any reporting period. To calculate an annual availability number based on monthly data, you can sum the monthly time or production values before doing the same math, or take an energy-weighted average of the monthly availability numbers. What about data gaps or QC? Unfortunately, we see data concerns very often at operating sites, and garbage in equals garbage out. Some meters and sensors will have redundancy onsite in case one fails, but if we run into data concerns due to whatever issues arise, all may not be lost. Even in a system-wide SCADA outage or memory failure, some form of data are always being collected or modeled onsite, and inferences can be made. As a couple examples: If an inverter power meter at a site with 5 central inverters starts to fail, but the inverter should still be online, an operator can verify the inverter’s availability using the POI (revenue) meter. The total power at the POI meter minus the power from the other inverters should roughly equal the power from the fifth inverter (“roughly” because of electrical losses and measurement uncertainties, which can generally be determined from operational data anyways). Even if the entire site goes offline for a period of time and no actual measured data is available, besides the power flowing to the grid at the POI, high-resolution meteorological satellite data can be used. Operators can observe the relationship between the solar resource and production during a fully-operational period to fill in the gaps and define expected production. Admittedly, many O&M providers will not go to the effort to fill in data gaps when they occur, which can lead to missing or inaccurate data. This, in turn, can lead to an inaccurate understanding of overall system performance, which in some cases can even impact a project’s valuation: availability is a key factor when reforecasting a project’s future production, and we have seen cases where missing data makes a significant difference in the uncertainty (leading to lower P99s). This is where Technical Advisors such as Camelot Energy Group can help ensure you are working with the most accurate data you can. Not only can availability be calculated based on a fundamentally different basis (time vs energy), but we need to be careful to scrutinize what is included in the definition as well. Until now, we’ve focused on System Availability, but you might find other metrics floating around and serving other purposes. A few common terms and measures are: System Availability - Captures all quantifiable downtime over the entire site for the entire period, with no carveouts. The following is a list of possible synonyms, noting that the definition of every availability metric should be scrutinized because they can be inconsistent: Plant Availability Project Availability Operational Availability Total Availability Overall System Availability (OSA) An inverter fire which caused system-wide availabilities to drop for a significant period of time Component Availability – Captures only the availability of an individual component over a given time. These commonly include inverter availability or module availability , but can be broken into any components, including trackers. Sometimes referred to as Manufacturer Availability . Contractual Availability – Sometimes also referred to as Guaranteed Availability, this metric is the most commonly-confused one of them all. It should be clearly defined in an O&M agreement, and the downtime it includes can vary. The denominator in the calculation is often more complicated than simple “total time” or “total production” during the period, and both parts of the equation can include carveouts for periods which are often deemed outside of the operator’s control. This is the most commonly-reported time-based availability, but we are seeing an increase in contracts which define Contractual Availability on an energy basis. This incentivizes operators to perform maintenance at more optimal (lower resource) times. Balance of System (BOS) Availability – Includes the availability of all components other than the modules and inverters, such as wiring, mounting structures, and monitoring equipment. Sometimes also termed Balance of Plant (BOP) Availability, but as always, the definitions must be scrutinized. Grid Availability – Captures downtime when the grid is not available to accept power generated by the project. This is the most common carveout for contractual availabilities, as it is almost always outside the control of the operator. We hope this moderately deep dive into solar availabilities helps to put the numbers into perspective and emphasize the importance of understanding what metrics you are looking at when evaluating a project’s uptime. We can always go deeper into the topic, and we’d be happy to support with any questions you may have. The next article in this series will cover a number of ways of maximizing availability and improving your metrics. In the meantime, for questions and more details about Camelot Energy Group and our distinct attitude towards these issues, please reach out at info@camelotenergygroup.com . About Camelot Energy Group is a technical and strategic advisor to owners and investors in clean energy and energy storage projects, programs, and infrastructure. Guided by our core values of courage, empathy, integrity, and service we seek to support the energy needs of a just, sustainable, and equitable future. Our team has experience in supporting 7+GW of solar PV and 10+ GWh of energy storage and offers expertise in technology, codes and standards, engineering, public programs, project finance, installation methods, quality assurance, safety, contract negotiation, and related topics. Our services are tailored to a providing a different kind of consulting experience that emphasizes the humanity of our clients and team members, resulting in a high quality bespoke service, delivered with focus, attention, and purpose. Key services include: -Technical due diligence of projects and technologies -Owner’s representative and engineer support -Strategic planning -Training and coaching -Codes and standards consulting -Contract negotiation and support < Back Back

Nov 6, 2025 The Future of Grid - Scale Storage Grid forming projects: Should developers want to design grid-forming inverters they will need to engineer their systems differently. This means that auxiliary loads and losses will be higher, and economics will need to be re-casted to account for SoC-loss during standby operation and forming operation In addition, the following challenges must be navigated: Transformer inrush control POW switching or V/f pre-flux ramp for soft energization Over-voltage issues Handling reactive power absorption Resonance and harmonics Damping network oscillations and ensuring stable short-circuit response Frequency and load pick-up challenges Stabilizing V/f during cold load pickup and staged block loading Operational sequencing Q-droop hierarchy, staged energization, etc. validated via EMT and HIL tests Synchronization issues Smooth ramping, droop control, etc. Ramp rate tuning Staged load pickup and reserve margins Raafe Khan and Shawn Shaw < Back Back

Apr 4, 2025 New U.S. Tariff Policy In an Executive Order signed on April 2, 2025, President Trump has instituted a minimum 10% universal tariff on all imports starting April 5. These 10% tariffs will be additional to “Reciprocal Tariffs” between 10% and 50% on products from about 60 countries starting April 9. The Trump Administration has calculated these Reciprocal Tariffs based on the ratio of country-level trade deficits with the US divided by the value of US imports from the target country. This ratio is being described as a measure of perceived unbalanced trade practices against the US and the Reciprocal Tariffs are being set at 50% of this value for most countries. We note that there are a variety of reasons for countries to have trade deficits and the existence of such deficits is not, in its own, an indication of unfair or unfavorable trade policies. It merely conveys that the US buys more of a country’s exports than that country buys of US exports and these deficits are a normal part of global trade between nations. Exceptions ➡️These new tariffs will not apply to goods that have been loaded on a vessel at a port and are deemed to be in transit before the new rates go into effect. ➡️The universal rate will not apply to goods in transit to the US before April 5 and the reciprocal rates will not apply to goods in transit to the US before April 9. ➡️According to the Executive Order, the new tariffs will not apply to certain articles that President Trump has already singled out for current or possible future sector-specific tariffs. Per the National Electrical Contractors Association (NECA), these sectors are steel, aluminum, some downstream products that use steel or aluminum, copper, pharmaceuticals, autos and auto parts, semiconductors, certain critical minerals and energy and energy products. ➡️The tariffs apply only to the non-US content of goods that include US components. However, at least 20% of the value of such goods would have to originate within the US. Implications for the Energy Sector The new tariffs will impact a variety of energy related technologies, from solar modules produced in Vietnam to wind turbines made with foreign components. FERC recently released their Energy Infrastructure Update for January 2025, in which they noted that the vast majority of new generating capacity will be in solar and wind . Other equipment necessary for bringing power plants online, like switchgear, transformers, and substation equipment is largely imported and will see costs increase. The fossil fuel industry is not exempt, either. Thermal generation equipment, like natural gas combined cycle (NGCC) turbines. Supply is already constrained, and capacity is tied up until about 2029-2031 from Tier 1 suppliers, so added costs will add even more strain. The broad application of new tariffs is expected to have an impact across the energy sector, from gas turbines to solar modules, just as energy demand is growing nationwide to fuel the growth of the AI sector. Impacts on the Energy Storage Supply Chain Many of the countries that supply battery energy storage systems (BESS) to the US market are heavily impacted by the new tariffs. As it currently stands, assuming no other changes, by January 2026, BESS from China will be subject to a total tariff of about 82.4%, as shown below. Clearly, juggling all of the relevant tariffs and duties is a significant exercise with many moving parts. *HTSUS = The Harmonized Tariff Schedule of the United States Tariff Rate Base Tariff, applied March 2025 20.0% HTSUS* Tariff (2012) 3.4.0% Section 301 Tariff 7.5% (2025), 25.0% (2026) Reciprocal Tariff 34.0% Total 64.9% (2025), 82.4% (2026) A summary of the major BESS exporting countries to the US and their new tariffs is shown below. Imported BESS from China have a significantly higher expected tariff than most other countries exporting BESS into the US market. The final tariffs on any product, however, will be complicated to determine as the underlying components may, themselves, be subject to additional tariffs (e.g., an Indonesian BESS made with Chinese inputs). This will be most impactful to the lithium iron phosphate (LFP) BESS suppliers in the near term but with no country being exempt from at least some sort of tariff, we can expect a great deal of supply chain adjustment in the months ahead. Country HTSUS Tariff Base Tariff Section 301 Tariff (Before 1/1/26) Section 301 Tariff (After 1/1/26) US Reciprocal Tariff Total New Tarriff Rate in 2025 Total New Tariff Rate in 2026 China 3.4% 20.0% 7.5% 25.0% 34.0% 64.9% 82.4% Indonesia 3.4% 10.0% 0.0% 0.0% 32.0% 45.4% 45.4% South Korea 3.4% 10.0% 0.0% 0.0% 25.0% 38.4% 38.4% Japan 3.4% 10.0% 0.0% 0.0% 24.0% 37.4% 37.4% Impacts on Battery Storage Pricing Based on our tariff tracker, Chinese made DC blocks are now effectively between the $130 - $180 per kWh-dc range (DDP to site), whereas Non-Chinese DC blocks (manufactured in let’s say Indonesia) are between the $115 - $165 per kWh-dc range (DDP to site). Baseline costs are expected to shift in the near term so this gap may narrow or widen further based on macroeconomic conditions. The gap between domestically manufactured non-LFP DC blocks and Chinese made LFP blocks is expected to narrow by early next year to about $50-$60 per kWh-dc. This means, if OEMs in this category reduce their prices by about 25-30%, based on current capacity projects, then, domestically manufactured non-LFP BESS will be a more attractive option for buyers based on total cost of ownership, not inclusive of the domestic content adder under the IRA. It is to be noted that the American Active Anode Material Producers (AAAMP) filed an AD/CVD petition in 2024 seeking a tariff of up to 910%. This has not yet been adjudicated by the Department of Commerce; however, we expect some movement on this later this fiscal year. Chart from Camelot Energy Group – Impact of April 5 Tariff on DC Blocks International Reactions The scale of the current trade actions is highly likely to elicit stiff responses from the international community. As of this morning of 4/4/25, China has announced a 34% tariff on all US imports, alongside increased export controls affecting rare earth minerals and other key materials exported to the US. While the US is a net importer of most clean energy technologies, US exports of biofuels and components for wind and hydropower systems may be impacted. Perhaps even more impactful, however, would be an increase in export controls that reduce the availability of key input materials. Efforts to onshore lithium-ion battery production, for example, will struggle without a ready supply of high grade graphite for making suitable anodes (currently, despite recent AD/CVD claims, there are no domestic suppliers of graphite who can meet the battery industry’s purity requirements). Also, the majority of equipment used in manufacturing solar cells is currently sold by China, with one recent manufacturer Camelot spoke with indicating the only other option was to buy European equipment at “4x the cost and half the output” compared to the Chinese alternatives. If these trade actions are intended to spur a renaissance of domestic manufacturing, the US is highly vulnerable to interrupted supply chains and export controls from abroad that restrict the very tools we need to build and scale a domestic manufacturing industry. The global trade situation and its impacts on the clean energy sector are evolving quickly and this is a developing topic. Stay tuned for periodic updates from the Camelot team in the days ahead. Follow us on LinkedIn for the latest insights. Next Steps for Industry Stakeholders With growing pressure due to pricing, it is time to carefully evaluate projects and supply chain risks. The Camelot team can help asset owners, investors, and other key stakeholders: Perform due diligence on potential new projects, optimizing technology, revenue streams, and asset management strategy Establish, strengthen, and diversify supply chains to ensure you have flexibility to keep your projects on track Evaluate new technologies that may offer new opportunities, as well as new challenges The Camelot team combines technical, economic, procurement, and strategic insights to help our clients navigate the changing market. Reach out to Hello@CamelotEnergyGroup.com today. We look forward to hearing how the new tariffs affect your business- and ensuring you get the help you need. Bespoke technical and strategic advisory for a better world Raafe Khan, Shawn Shaw < Back Back

Aug 8, 2025 Camelot Unpacks UL 9540 – Part 1 At Camelot, reviewing the UL Listing status of battery energy storage systems (BESS) for the projects we are overseeing as an Owner’s Engineer (OE) or Independent Engineer (IE) is something our team considers a good starting place in the due diligence process. This Listing is so foundational to a successful and code-compliant BESS project that we often take it for granted that everyone understands what this important Standard entails.   Unfortunately, there is a great deal of misunderstanding about the UL 9540 Listing process, even among some engineers who are otherwise pretty familiar with BESS technologies. Missing a step in verifying the proper UL listing of the BESS on a project can have large implications. For instance, an astute authority having jurisdiction (AHJ) that notices your BESS is not properly Listed may find it is not code-compliant, causing significant delays in permitting and significant costs in addressing deficiencies with the BESS manufacturer. Moreover, a UL 9540 Listing represents the successful completion of a battery (we could not resist, of course) of tests related to safety, reliability, and performance.   Understanding Standards Most folks involved in BESS projects think they know what a Standard is, as it seems pretty self-explanatory, right? Perhaps, but once you move beyond the surface level and try to parse the difference between a “Listed”, “Certified”, and “Recognized” product, it can quickly get confusing. So, let’s address a few common misconceptions.   Misconception 1: Projects Have to Comply with Standards The rollout of new standards, like NFPA 855 and UL 9540, have undoubtedly made BESS projects safer. However, complying with these Standards is not required. Organizations like NFPA or UL have no legal authority to provide, or deny, any project a permit. Permits are issued, rather, based on Codes (e.g., Electrical Code, Building Code, Fire Code) and if the Code for your project’s jurisdiction does not incorporate one of these Standards, then the AHJ may not be able to enforce the requirement. This can happen, for instance, when a local Code has not been updated recently enough to incorporate the latest versions of relevant Standards. So, unless the Code references a particular Standard, the project does not have to comply with the Standard, at least from a permitting perspective. Fortunately, many savvy asset owners have developed their own BESS technical criteria. While these criteria are unrelated to permitting, they can be used as a condition of financing. In this way, the investment community can drive better and safer installations by holding developers to the highest current Standards (literally). Misconception 2: Standards Represent the Gold Standard of Safety and Quality Given all the time taken, and the expertise of the dozens of industry experts applied, in crafting Standards it is natural to assume that each one represents the pinnacle of current thinking in design, safety, and quality. Not so. It is best to think of a Standard as the lowest common denominator that a bunch of technical folks with often-competing priorities can agree on. Anyone that has ever got more than one engineer in a room to talk about BESS likely knows that we can be an opinionated bunch, so imagine what a room with fifty engineers is like when coming up with a new technical Standard. The results are incredible acts of service to the industry, but they are only a starting place. Complying with Standards should be a bare minimum, not a stretch goal.   Misconception 3: A BESS can “Pass” or be Listed to UL 9540A Most folks understand a Standard as something that can be “passed” or “failed”. This is an understandable interpretation, as it applies to everything from everyday household appliances to BESS equipment. Unfortunately, UL 9540A is a little different. UL 9540A is actually a testing Standard that describes how a testing laboratory is to initiate and measure the impacts of thermal runaway . In completing the tests, it is literally impossible to not destroy the BESS (/ the BESS is intentionally destroyed). If thermal runaway is not initiated through one initiation method (e.g., heating), then the test continues using other methods until thermal runaway occurs (e.g., nail penetration, overcharging). There are non-lithium-ion BESS that are not subject to thermal runaway but even these do not “pass”. Instead, at each level of testing, a higher level of testing is required unless the test results fall within a particular range . For example, if a cell is tested and does not exhibit thermal runaway, it is not required to test at the module or unit level.   Misconception 4: UL 9540 Replaces Other Battery Standards In fact, UL 9540 is carefully crafted to build on other key standards, not replace them. Though many spec sheets will list UL 9540 alongside UL 1973 or UL 1741, compliance with UL 9540 already includes many of these relevant equipment-specific Standards , such as: UL 1973 for battery cells and modules UL 1741 for inverters (such as in AC block BESS products) UL 9540A for testing thermal runaway propagation risks   Wrapping Up Part 1 Misunderstandings about UL 9540 aren’t just academic - they can cause costly delays, strained relationships with AHJs, and headaches during financing or commissioning. Clearing up the myths is the first step, but knowing exactly what UL 9540 covers, when it’s required, and how to navigate the Listing or Field Listing process is where the real project-saving insight comes in. In Part 2, we’ll take that next step: unpacking the key requirements baked into UL 9540, explaining how they connect to other Codes and Standards, and clarifying the often-misunderstood Field Listing process. If Part 1 was about avoiding the traps, Part 2 is about charting the course to a compliant, bankable BESS installation. < Back Back

Nov 7, 2024 Part 2: VDER Revenue Stack As discussed in Part 1: VDER Revenue Stack for Standalone Storage Projects , while the Value of Distributed Energy Resources (VDER) Calculator is a freely accessible tool for estimating expected VDER revenues, it can fall short in accurately modeling certain revenue streams. Therefore, when evaluating investments in Battery Energy Storage System (BESS) or hybrid (solar + storage) projects, it’s crucial to supplement this initial analysis with a more detailed revenue forecast that considers additional variables encountered in real-world operations. Like other leading market analytics providers, Camelot uses an optimized dispatch model to project future revenues for BESS and hybrid projects participating in merchant energy and ancillary services markets. However, projects with substantial programmatic revenues—such as NY VDER projects—often require a more customized approach to accurately validate revenue streams and financial model inputs. To address this need, Camelot has developed additional tools and capabilities that seamlessly integrate these programmatic revenue streams with relevant merchant market opportunities. You can find more background on the VDER program here to help developers and investors understand this critical framework. For our analysis, we modeled the revenue stack of a hybrid system with a 5 MWDC solar array and a 5 MW, 4-hour BESS under the VDER program across various utilities. We estimated the Locational System Relief Value (LSRV) manually, while our optimized dispatch model calculated LBMP, ICAP Alt 1, ICAP Alt 2, and DRV values. Additionally, we created four scenarios based on the following configurations: Hybrid Systems – PV Charging Only PV Charging Only (Alt 1) PV Charging Only (Alt 2) Hybrid Systems – PV & Grid Charging PV & Grid Charging (Alt 1) PV & Grid Charging (Alt 2) Key Trends and Insights from the PV Charging Only Results Figure 1 Excerpt from Camelot Q4 2024 NY Market Outlook Report Figure 2 Excerpt from Camelot Q4 2024 NY Market Outlook Report Energy Component (LBMP): The combined energy (LBMP) values from both BESS and solar in PV Charging Only projects are not the lowest among VDER components when compared to standalone BESS projects. This is largely because there are no charging costs—BESS charges from PV rather than the grid. Installed Capacity (ICAP) Value: Capacity prices vary significantly by NYISO load zones, making capacity revenue forecasts challenging due to price volatility across zones. These prices may decline as offshore wind is integrated, which contributes both energy and capacity. ICAP Alt 2 yields higher revenue than ICAP Alt 1 across all zones, primarily due to the rate structure of ICAP Alt 2. Similar to ICAP Alt 3 (applicable only to standalone BESS), ICAP Alt 2 prices have historically been higher, especially in Zone J (NYC – ConEd Group A) and Zone K (PSEG LI). Zone J prices average 3.04 times higher than other zones due to anticipated thermal retirements and land constraints that limit new renewable integration. Demand Reduction Value (DRV): Like standalone BESS projects in areas with 2 PM to 7 PM DRV windows, PV Charging Only projects also achieve strong DRV results as these hours often align with system peak windows. In ConEd Group B (Westchester), projects within the 2 PM to 6 PM DRV window produce significantly higher DRV revenues compared to those in the 2 PM to 7 PM window, as the former aligns more closely with potential peak periods. For instance, DRV revenue in ConEd Group B is 6.36 times higher than the utility average within the 2 PM to 7 PM window and 5.82 times higher than the state average. Locational System Relief Value (LSRV): In Central Hudson’s territory, LSRV does not apply. However, the highest LSRV revenues are seen in ConEd (Zones A to C) and PSEG territories, where LSRV revenues are 2.60 times higher than the state average. Environmental Value: The environmental value remains constant across all utilities and is locked in for 25 years. This revenue stream applies only to PV Charging Only cases in VDER, making these configurations more attractive than PV & Grid Charging due to the additional revenue stream. Key Trends and Insights from the PV and Grid Charging Results Figure 3 Excerpt from Camelot Q4 2024 NY Market Outlook Report Figure 4 Excerpt from Camelot Q4 2024 NY Market Outlook Report Energy Component (LBMP): In PV & Grid Charging projects, the combined energy (LBMP) components from both BESS and solar, including charging costs, are the lowest revenue component when compared to PV Charging Only projects in VDER. This is largely because PV Charging Only projects incur no charging costs, as BESS charges directly from PV rather than the grid. Installed Capacity (ICAP) Value : Capacity prices vary significantly by NYISO load zones, making capacity revenue forecasting challenging due to price volatility across zones. These prices could decrease with the addition of offshore wind, which contributes both energy and capacity. Like PV Charging Only projects, PV & Grid Charging projects see higher revenues under ICAP Alt 2 compared to ICAP Alt 1 across all zones, primarily due to the higher rate structure of ICAP Alt 2. Like ICAP Alt 3, which applies only to standalone BESS projects, ICAP Alt 2 prices have historically been highest in Zone J (NYC – ConEd Group A), followed by Zone K (PSEG LI). Zone J averages 3.06 times higher than other zones, driven by anticipated thermal retirements and land constraints that hinder new renewable integration. Demand Reduction Value (DRV): Similar to standalone BESS projects in regions with 2 PM to 7 PM DRV windows, PV & Grid Charging projects also achieve strong DRV results as these times often align with system peak periods. However, as with PV Charging Only projects, PV & Grid Charging projects in ConEd Group B (Westchester) within the 2 PM to 6 PM DRV window yield much higher DRV revenues than those in the 2 PM to 7 PM window, as the former more closely overlaps with system peaks. For example, DRV revenue in ConEd Group B is 5.95 times higher than the utility average within the 2 PM to 7 PM window and 4.87 times higher than the state average. Locational System Relief Value (LSRV): In the Central Hudson territory, LSRV does not apply. Similar to PV Charging Only projects, the highest LSRV revenues are observed in ConEd (Zones A to C) and PSEG, where LSRV revenues are 2.73 times higher than the state average. Environmental Value: The environmental value applies exclusively to PV Charging Only cases within VDER, making PV & Grid Charging cases less favorable in the VDER revenue stack due to the lack of this additional revenue component. Conclusions The VDER revenue stack significantly diminishes for projects located outside of ConEd and PSEG territories. Although CAPEX and OPEX costs for upstate projects may generally be lower, this advantage is offset by the more lucrative revenue streams available in ConEd and PSEG regions, as highlighted in this article. When calculating these revenue streams, it’s essential to account for the various market nuances specific to the VDER revenue stack, as discussed in Part 1: VDER Revenue Stack for Standalone Storage Projects. While the VDER Value Stack Calculator is a useful tool for preliminary analysis, it may not always provide accurate forward revenue estimates. Our team recommends conducting a more detailed analysis to support the development and financing of energy storage and hybrid projects in New York State. In summary, when comparing the VDER value stack for hybrid projects under ICAP Alt 1 and Alt 2, as well as the PV Charging Only and PV & Grid Charging options, we find that PV Charging Only (Alt 2) projects generate higher revenues than PV & Grid Charging projects. This is primarily due to the Environmental value, which is locked in for 25 years at a fixed rate of $31.03/MWh, and the increased revenue potential that ICAP Alt 2 offers over Alt 1. To accurately assess the benefits of PV Charging Only versus PV & Grid Charging, Camelot can assist you in determining the optimal storage system size to co-locate with your solar system, helping you maximize returns for hybrid projects. If you're interested in assessing energy storage and/or hybrid projects in NYISO’s VDER Program, feel free to reach out to us at info@camelotenergygroup.com . About Camelot Energy Group is a technical and strategic advisor to owners and investors in clean energy and energy storage projects, programs, and infrastructure. Guided by our core values of courage, empathy, integrity, and service we seek to support the energy needs of a just, sustainable, and equitable future. Our team has experience in supporting 7+GW of solar PV and 10+ GWh of energy storage and offers expertise in technology, codes and standards, engineering, public programs, project finance, installation methods, quality assurance, safety, contract negotiation, and related topics. Our services are tailored to a providing a different kind of consulting experience that emphasizes the humanity of our clients and team members, resulting in a high-quality bespoke service, delivered with focus, attention, and purpose. Key services include: -Technical due diligence of projects and technologies -Owner’s representative and engineer support -Strategic planning -Training and coaching -Codes and standards consulting -Contract negotiation and support. < Back Back

Dec 4, 2025 CAISO Market Operations CAISO Market Refresh CAISO is the second largest renewable energy market by deployment, just marginally behind TX, however, operating in CAISO isn’t trivial – the market works in a few layers, and all required capacity is procured in the DA market However, two additional balancing markets run throughout the day – the Integrated Forward Market (IFM) and the Fifteen Minute Market (FMM) Source: CAISO OASIS Data Integrated Forward Market (IFM): Bidding starts in the IFM the morning before the day starts and all operators submit bids for DA and AS for each operating hour. However, BESS with Resource Adequacy (RA) contracts are required to make bids for every hour Fifteen Minute Market (FMM): Once the day begins, FMM gets to work. Operators must submit bids 75 minutes prior to each operating hour. This is also referred to as the 75-minute lockout period FMM capacity is cleared in 15-minute increments Real-Time Dispatch (RTD): RTD works in 5-minute intervals and CAISO uses this to address sudden system wide issues like outages, demand spikes, etc. FMM awards can be adjusted in both directions in RT, and this can cause uncertainty about the immediate operating hours. It is important to note that assets with firm AS obligations must have 60-minutes of SoC in the IFM and 30-minutes of SoC in the RTM to deliver and avoid penalties. Key Market Mechanisms & Initiatives Extended Day-Ahead Market (EDAM): This is a major ongoing initiative to expand the real-time WEIM into a day-ahead market. Status: The EDAM is scheduled to launch in May 2026, with PacifiCorp and Portland General Electric as initial participants. Stakeholder workshops are ongoing to finalize tariff clarifications and implementation details. Source: U.S Energy Information Administration Flexible Ramping Product (FRP): This market mechanism is designed to manage the significant net load variability caused by high solar and wind integration. Function: It procures capacity to handle forecasted movement and uncertainty in net load (total load minus solar/wind generation) in the real-time market. Performance & Challenges: The CAISO net load can swing more than 20 GW in a single hour. While beneficial for grid stability, the FRP rarely presents consistent, high-value revenue opportunities for most battery energy storage systems (BESS) as prices are often zero due to sufficient available capacity. The Department of Market Monitoring has previously identified implementation errors in the product's demand curve calculations that resulted in under-procurement of upward capacity during critical ramps. FRP addresses real-time variability across the Western grid, with CAISO facing some of the steepest ramps Source: U.S EIA SP15 hosts nearly 75% of CAISO’s battery storage, reflecting where solar growth and ramping needs are most concentrated. This regional buildout plays a major role in shaping real-time flexibility and FRP activity across the grid. As storage scales further, SP15 increasingly influences CAISO’s price formation and operational dynamics. Source: CPUC Master Resource Database Ancillary service prices in SP15 have declined sharply as battery storage has scaled across CAISO. With increased competition, services like RegUp, Spin, and Non-Spin offer far less revenue than previous years. This shift pushes storage operators to rely more on energy arbitrage and real-time market opportunities. Source: CAISO OASIS Data With ancillary service prices declining, energy arbitrage now makes up the largest share of CAISO BESS revenue. Growing solar-driven volatility has increased DA–RT spreads, making arbitrage more valuable. As a result, storage operators rely more on price forecasting and real-time optimization to capture returns. Source: CAISO Special Data TB4 opportunities come from predictable daily price swings in CAISO, where low midday prices encourage charging and high evening prices reward discharging. This spreads-based strategy is a major revenue driver for batteries under tolling agreements. Capturing these spreads consistently requires strong forecasting, SOC planning, and real-time optimization. Source: CAISO OASIS Data California utilities and CCAs are rapidly increasing their TB4-settled procurement, growing from under 2 GW in 2023 to over 3.5 GW by 2025. TB4 contracts shift real-time operational risk from offtakers to independent power producers (IPPs). This structure gives utilities financial certainty while requiring storage operators to manage price volatility and dispatch performance. The growing adoption of TB4 highlights the market’s move toward financially settled performance-driven contracting for BESS. Source: CPUC Fillings Raafe Khan < Back Back

Sep 11, 2024 Solar Availability Series Part 4 Welcome back for Part 4 of Camelot’s series on solar availability. If you’re just joining us for the series, here are some links to parts 1 , 2 , and 3 . We’ve set the groundwork with a summary of the ongoing validation efforts from IEs, and the resulting changes the industry is making to their assumptions. We’ll revisit their reasoning here. We’ve also described how availabilities are calculated and reported, and touched on ways of maximizing availability by minimizing downtime. If you’ve followed along with the last few parts and you’ve been waiting for our own stance as an Independent Engineer (IE), look no further! Thank you for joining us. Re-Setting the Scene Until somewhat recently, the utility-scale solar industry didn’t have the kind of established history needed to accurately predict or validate what long-term average availabilities will be at newly-proposed projects. Engineering judgement said that a relatively simple solar project would see the equivalent of about 3-5 days of total site outages per year, leading to expected availabilities of about 98.5% to 99.2%. For modeling simplicity, most everyone assumed a relatively consistent availability throughout a project’s lifetime. However, as projects became operational, the industry started to question itself. Especially early in new projects’ operational lives, downtime was high and availabilities were lower than expected due to teething issues. Even after the initial startup period, many folks started seeing trends with their average availability levels below what they had hoped. Over the last year we have started to see the beginnings of some robust data-backed approaches to redefining availability assumptions, aided by all the new operating data which is available to us. There have been three IEs who have recently updated their assumptions based on aggregated data from the projects they supported. ICF led the charge with its performance paper published by kWh Analytics in 2023. DNV and Natural Power followed suit with their own methodology updates in early 2024. Others with access to the data have weighed in as well, from NREL to kWh Analytics. Here, we focus in on the results of the IE validations, each of which took slightly different approaches and used different data sets. The table below summarizes the projects which went into the IEs’ comparisons, and some key comments from their results. We’d like to highlight a few key findings from this comparison: Every IE relied on data from monthly operating reports produced by the operators, which are rarely independently calculated or verified. As described in part 2 of this series, there is no single, standard way that availabilities are defined or reported across the industry. The conclusions from these studies should be interpreted carefully, especially because the data QC processes have not been explicitly described. DNV’s analysis used more data and resulted in recommendations which are more clearly tailored to the sites. ICF found that fixed tilt systems showed lower availabilities than tracker systems while DNV found the opposite. Despite every IE noting lower availabilities early in a project’s life, only DNV adjusted their recommendation to treat the first year differently from other years. No IE has taken a stance on availability changes later in a project’s life yet. Here is a summary of the IE’s post-validation default availability recommendations. As you can see, only DNV makes a distinction between different kinds of projects at this time, though every IE noted that they are open to changing their assumptions based on project-specific data such as operator or technology history. In practice, however, IEs are often reluctant to deviate from their standard assumptions, as this requires going out on a proverbial limb. While that conservatism is understandable, it may be producing unintended consequences. For instance, if an IE will not give “credit” for more robust technology choices or operating strategies, then owners have little incentive to consider any options but those that can be considered “bankable” at the lowest possible cost. This approach penalizes owners for considering better than baseline equipment, spending more on O&M, or otherwise looking for creative solutions to improve availability. The need for more data was a theme repeated by each company, and this will likely ring true for as long as we do this kind of work. Our availability assumptions will need to be updated regularly, just like we update our approaches to Energy Yield Analyses. Camelot’s Recommendations The Camelot team is compiling the data needed to supplement these studies and validate our conclusions, and we welcome the opportunity to work with industry partners on this effort. In the meantime, we base our own recommendations off the meta-study described above and in Part 1. Without further ado, here is our own take on availability projections: Until we have more information, we should not be differentiating between different mounting types . ICF’s and DNV’s observations contradicted each other. It’s likely other factors influenced the analyses, especially the sample sizes and quality of the input data. The factors which can impact downtime should be studied further, which means collecting more data, ensuring its accuracy, and capturing all potentially-relevant project details. In addition to mounting types, the difference between inverter technologies must be studied further as one of the primary sources of downtime observed at operating sites. For instance, the higher availability noted by DNV on smaller fixed-tilt sites than larger fixed-tilt sites may indicate a reliability advantage for string inverters over relatively small sites with central inverters. This would align with our general experience with operating sites but the data to positively confirm this is not yet available in sufficient quantity. The major sources of downtime should be studied and modeled separately . Using an overall system availability as a metric can muddy the waters significantly, especially when trying to tease out the impact of different design decisions on future performance. When performing energy yield analyses for wind energy projects, some IEs will include assumptions for balance of plant availability, grid availability, and turbine availability separately. Not only can this improve our validations (data allowing), but it will improve the way we assess technology tradeoffs at the design stage. Swapping out a more robust system for a less-robust one should impact only the downtime assumption for that system. Camelot recommends the industry work towards a bottom-up availability model based on historical failure/downtime data at the module, tracker, inverter, MV, HV, and BOS levels. These levels correspond with likely failure points within the system and provide a lowest common denominator that can be adjusted during project design to optimize expected availability. Ensuring this approach has buy-in from IEs will provide a financial incentive to specify better equipment and design better sites. Year-1 availability should be modeled separately from later years due to initial startup issues observed in each validation. Nearly all financial models are already set up to account for annually-varying losses, so adjusting our assumptions based on the clear signals we see from the data appears to be a no brainer. The industry should start modeling a ramp-down in availability later in projects’ life, as DNV may have alluded to, because component failure rates impact availability trends. Without more data, it is difficult to say the magnitude of the decreases because of the other factors at play. However, based on our experience modeling availability at other infrastructure projects, Camelot considers it reasonable to model availability as a ramp-down as a project nears the end of its design life. The “bathtub curve” shown below is an Engineering concept which supports this idea. It shows how infant mortality failures likely contributed to the observed availabilities in the first 6-12 months of operation, and highlights the further need for more operational data as projects age. This is applicable to individual components in many physical systems. Aggregated across an entire system and accounting for typical replacements and maintenance, one might expect to see a flatter availability curve, but with some consideration for early- and late-stage failures. We have seen this already with 10-15 year old PV sites, where owners struggle to obtain compatible replacement equipment that can be “dropped in” to replace original equipment onsite. As technology continues evolving quickly, we can expect new module types, inverter technologies, sensing devices, and code requirements to all play a role in the maintainability of PV sites in the late stages of their useful life. Camelot’s Balanced Approach The summary below provides a graphical representation of each IE’s default availability recommendations over time, and includes Camelot’s own recommended defaults (when no other project-specific information is available). We note the following: Camelot’s approach accounts for the size impacts observed by DNV, which appears to be a strong signal in the data, but does not differentiate between technologies until more information is made available supporting the distinction. Much like DNV, Camelot’s recommended availability starts slightly lower in year 1 before reaching steady operations, as is supported by all studies. We recommend modeling availability declines after year 20 based on several factors, including the bathtub curve concept described above, the typical useful life for major components, and our expectation that the impacts of mid-life failures will likely offset by the efficiencies gained from experience during operations. While we see this assumption as a necessary recognition of late-stage wear-out failures, it’s worth noting that its impacts on a financial model are muted by the time value of money. On average, Camelot’s assumptions are less pessimistic than ICF, and strike a balance between the assumptions reported by Natural Power and DNV. Camelot will consider quantitative adjustment to our base availability assumptions for sponsor efforts that materially result in increased reliability, such as: Demonstrating better than average historical availability for project- specific equipment (e.g., inverters) through operational data (as described in item 3 above) Adding incentives to O&M Agreements for increased availability, beyond simply guaranteed levels Purchasing extra spare parts for more vulnerable system components likely to need frequent replacing Investing in predictive analytics and above-market O&M services to reduce the frequency and severity of unplanned maintenance events While these recommendations may be Camelot’s “default” values, as an IE which cares heavily about the accuracy of our projections, we will always consider factors such as operator experience or the relative track record of the technologies deployed at each site. As the saying goes, “show us the data.” Before we close, it is important to underscore an important point. Recent reporting that indicates PV projects are falling short of expected availability is a call to action for all of us. It is a call to action for more data, better analysis, and a deeper understanding of what causes PV systems to underperform. It is, notably, not a call to action for unnuanced conservatism. Simply whacking a few points off availability is, in our view, insufficient to the task of ensuring a better-performing PV fleet and it creates blind spots. We hope our fellow IEs will join us in not simply erring on the side of conservatism but, rather, will continue to advance our knowledge of these issues and build better, and more nuanced models that reward innovation, investment, and effort. We hope you’ve found this series to be helpful, and we welcome the opportunity to partner with any of our readers who would be able to support with future efforts. Although this is the last of our solar availability series for now, we fully intend to revisit the topic in the future. For our storage-oriented audience, you can expect a similar discussion on availability assumptions for BESS technologies in upcoming articles. About Camelot Energy Group is a technical and strategic advisor to owners and investors in clean energy and energy storage projects, programs, and infrastructure. Guided by our core values of courage, empathy, integrity, and service we seek to support the energy needs of a just, sustainable, and equitable future. Our team has experience in supporting 7+GW of solar PV and 10+ GWh of energy storage and offers expertise in technology, codes and standards, engineering, public programs, project finance, installation methods, quality assurance, safety, contract negotiation, and related topics. Our services are tailored to a providing a different kind of consulting experience that emphasizes the humanity of our clients and team members, resulting in a high quality bespoke service, delivered with focus, attention, and purpose. Key services include: -Technical due diligence of projects and technologies -Owner’s representative and engineer support -Strategic planning -Training and coaching -Codes and standards consulting -Contract negotiation and support. < Back Back

Jan 14, 2025 New Acquisition Opportunity in ERCOT At Camelot, we always try to keep a finger on the pulse of the solar and energy storage M&A market, as many of our clients turn to us for technical and market due diligence on these sorts of engagements. We just had a noteworthy M&A opportunity come across our desk from our friends at Enerdatics and wanted to share this opportunity with our network. It’s for one hybrid (Solar + BESS) project in ERCOT – a region where many folks have had development and acquisition interests. A few details to highlight: Project located in Reeves County (West Hub) Point of Interconnect PV Capacity is 16.1 MWdc and BESS Capacity is 28.2 MWh (Assumed to be a 2-hour battery with an overbuild). It’s designed to participate in ERCOT as a Settlement-Only Distribution Generator (SODG) with Clip Charge and Energy Arbitrage. Solar PV will employ bifacial modules with single-axis tracker and the BESS equipment will use Li-ion technology. Interconnection is planned with Texas New Mexico Powe Company (TNMP), with a 12.47 kV voltage specification, connected to a substation, which is 0.3 miles from project to Point of interconnect. Key milestones such as the completion of Initial Assessment (IA) studies and Phase I ESA have been achieved for both sites. Due to its location, there are no county requirements for environmental permitting. Given the project size, state permitting requirements are also favorable. Lease agreements for 30+ years have been secured Approx. 70 Acres secured, possibly allowing future additional buildout Anticipated COD in Q4 2025. Camelot has recently performed diligence on, and supported the development of, several projects in ERCOT (“TX 10’s”) and we find that revenues can vary widely based on the specific node, though volatility in the region is moderate and favorable to BESS project economics. The DC-coupled configuration is somewhat unique to the market, allowing clipping capture from the solar side, but making market participation more difficult; In ERCOT, regardless of the coupling configuration, the solar and the BESS systems apply for interconnection separately. Camelot also has recent data on CAPEX and OPEX applicable to the region, and can perform a wholistic economic analysis of the projects to verify the seller’s assumptions. Overall, depending on the quality of the development of course, this could be good opportunities in an active market. If you are new to the ERCOT market and/or BESS considerations, feel free to check out our relevant articles: www.linkedin.com Ahead of the Curve: How to Choose Forward Curves for BESS Projects Tips For Selecting Optimal Forward Curves for Energy Storage Projects with Mina M. Hanna Last week we introduced why accurate forward curves are critical. www.linkedin.com ERCOT Auxiliary Services for Energy Storage Systems Overview ERCOT purchases ancillary services in the day-ahead market to balance the forthcoming day's electricity supply and demand on the grid and address real-time operational challenges. These services, which can be offered by either generators or consumers, allow for rapid adjustments to the electricity s www.linkedin.com Understanding BESS Augmentation in the Renewable Energy Landscape Modern Battery Energy Storage Systems (BESS) lose available energy capacity as they age and are used to store and discharge energy. As such, many asset owners must carefully consider their approach to maintaining energy capacity throughout the useful life of the BESS. If you are interested, we would be glad to put you in touch with our friends at Enerdatics who are tracking the deal and, of course, if you decide to pursue and need any help on the due diligence side of things, please reach out to Taylor Parsons or Shawn Shaw, PE. < Back Back

Aug 8, 2025 Camelot Unpacks UL 9540 – Part 2 In Part 1 of our Camelot Unpacks UL 9540 series, we tackled some of the most common misconceptions about this critical Battery Energy Storage System (BESS) Standard - misconceptions that can easily derail schedules, inflate costs, or cause compliance headaches. Now, it’s time to move from myth-busting to the nuts and bolts. In Part 2, we’ll walk through some key questions regarding the requirements baked into UL 9540, highlight when and why it’s required, and shed light on the often-misunderstood Field Listing process. Whether you’re overseeing a project, supplying equipment, or working on the financing side, this is the knowledge that keeps your BESS project both compliant and bankable. What does UL 9540 include? While no product certification is ever a perfect guarantee of safety, the UL 9540 Standard is fairly broad in its scope as it's intended for an ESS as a whole, with key tests summarized below. These tests are additional to compliance requirements related to materials, construction, software, electrical design, fire safety design, noise levels, and more. These tests are also additional to any component-level tests required. For example, UL 1973 includes about 30 different tests on the battery modules alone, covering a range of potential risks, such as overcharging, over-temperature operation, external fire exposure, and physical impacts. Table 1: UL 9540 Key Tests Test Category Test Name Description   Electrical Safety Grounding & Bonding Ensures low resistance ground path to safely handle potential fault currents   Electrical Safety Electromagnetic Immunity Ensures safety sub-systems are not subject to electromagnetic interference and electrostatic discharge.   Electrical Safety Insulation Resistance Confirms insulation provides suitable impedance to prevent unintended current flow.   Electrical Safety Dielectric Voltage Withstand Confirms the suitability of dielectric materials to prevent current flow without breakdown.   Electrical Safety Impulse Test Assesses resistance to electrical surges. Fire & Thermal Safety Thermal Runaway Propagation Requires testing according to UL 9540A, with results incorporated into the system design. Mechanical Safety Leakage Confirms no leakage occurs when stress-testing liquid coolant systems with elevated pressure levels. Mechanical Safety Strength Confirms that elevated pressure in coolant systems does not cause damage to piping and equipment. Environmental Testing Seismic Confirms no major equipment damage after simulated seismic event. Environmental Testing Salt Fog Confirms resistance to marine environments. Environmental Testing Moisture Resistance Tests to confirm that enclosures properly resist water ingress. Other Operational Tests Normal Operating Verifies that ESS components do not exceed temperature ratings during normal charge/discharge behavior. Key Subordinate Standards Compliance with UL 1973 (Batteries) Ensures battery modules meet safety and performance standards. Key Subordinate Standards Compliance with UL 1741 (Inverters) Tests the safe integration of inverters in the system.   When is UL 9540 Listing Required? Compliance with UL 9540 is required under a number of major Codes, as summarized below. Note that, as of this writing, nearly all locations within the US require compliance with at least one of the Code editions noted below (or a more recent version). There are likely a few local jurisdictions not yet enforcing these Code editions but, essentially, Listing to UL 9540 is a Code requirement nearly anywhere in the US.     Referencing Code First Version Incorporating Listing for BESS Relevant Section(s) NFPA 70: National Electrical Code 2017 706.5 NFPA 1: Fire Code 2018 Chapter 52, which requires compliance with NFPA 855 which, in turn requires UL 9540 Listing in Section 9.2.1 (2023 Edition) IFC: International Fire Code 2018 1207.3.1   Is it Acceptable to Field List a BESS to UL 9540? Certainly, this is quite common and widely accepted. In practice (and in Code) an ESS is "one or more devices, assembled together, capable of storing energy to supply electrical energy at a future time". As you can see, this goes beyond simply the ESS enclosure to include the equipment facilitating connection to the broader electrical system, such as the inverter. Most ESS manufacturers will not have an infinite combination of their product listed with each possible DC converter, inverter, and transformer. As such, Field Listing is widely required to validate the "system" meets relevant Code requirements.   How does Field Listing Work? The term "Field Listing" is a slight misnomer, as the "field" portion is only a small part of the overall review. In fact, completing the Field Listing requires considerable review of documentation and generally requires that all the components of the ESS be Listed to their own respective Standards (see summary above). The Nationally Recognized Testing Laboratory (NRTL) doing the Field Listing will review the documentation and subordinate Listing status of all the major components in order to underpin their final Field Listing. As you can see, a successful Field Listing requires that the ESS uses high quality components that are properly Listed, and the Field Listing is really just validating the site-specific combination of those components (and that those components have been installed/used per their Listing). Once complete, the NRTL will issue a Field Listing that applies only to that specific project or installation. Even if the exact same equipment is used again at another site, a new Field Listing is still required. The pathway from Code requirement to (some of) the underlying Standards is summarized in the figure below. As you can see, a simple UL 9540 Listing has a lot behind it and is a critical element in having a high quality and bankable BESS. Figure 1: Compliance Pathway   Why do the Components Need to be Listed Separately for a Field Listing? Put simply, many of the required tests to List a BESS to UL 9540 are destructive in nature and you would not want them done to your commercial project. For example: UL 9540A testing requires initiating thermal runaway (aka making the system catch fire on purpose) Vibration and Impact Resistance tests may involve damaging your enclosures Overcurrent and overvoltage tests require exposing the BESS to electrical conditions beyond its design As you can imagine, few manufacturers would be willing to honor warranties after you abuse their system in such ways. So, since we can't deliberately set projects on fire in the field, the NRTL will have to rely on the test results used to obtain other component Listings. As shown above, the DC Block is already Listed to UL 9540. In these cases, all of the most strenuous tests have already been completed and found sufficient by a NRTL and the Field Listing can really focus on the combination of components. In some cases, NRTLs may be willing to issue Field Listings based on manufacturer test reports, engineering analyses, and similar documents but this is a very risky prospect and will take considerably longer and increase the cost to the owner. Also, if the NRTL finds they don’t have sufficient basis for granting the Field Listing, they may require additional testing from the manufacturer, leaving your project in a sort of Limbo state for months, if not longer. So, while any combination of ESS components can theoretically be granted a Field Listing, it is far safer to ensure your ESS is a combination of already-Listed components. In particular, using a DC block that is Listed to UL 9540 in its own right is a great way to reduce the risk of significant costs and/or delays in the final Field Listing process. < Back Back

< Back Shawn Shaw, PE Founder, CEO Shawn Shaw is the founder and CEO of Camelot Energy Group and has over 21 years of experience in the renewable energy and energy storage industry. During that time, Shawn has supported public programs in more than 10 states and acted as technical advisor to many of the largest banks and financiers in the world, providing technical due diligence, owner’s engineering, and independent engineering on well over 8 GW of solar PV and 5 GWh of energy storage projects in the US, Latin America, and Europe, ranging from design and construction of offgrid island power systems to acting as Independent Engineer for financing multiple 400MWh energy storage projects in complex US markets. Shawn has experience working with a wide variety of equipment suppliers, project developers, banks, financiers, government entities, and incentive program administrators. Shawn is a registered electrical engineer (Power Systems) in New York State and holds a B.S. in Applied Physics from Rensselaer Polytechnic Institute. Recently authored Energy Storage Systems: Based on the IBC, IFC, IRC, and NEC in collaboration with the International Code Council. shawn.shaw@camelotenergygroup.com

Apr 27, 2026 Round-Trip Efficiency Is Not a Spec Sheet Number - It's a System Behavior Under Load When we started looking at the data from ERCOT more closely, we couldn't help but notice that the AC RTE across the fleet is in the low-80s or high 70s, underscoring that RTE isn't a fixed property - it's an operating point. Here's what actually determines it: Cell/Module/Pack: I²R losses scale quadratically with current — high C-rate dispatch is inherently less efficient Internal resistance rises with decreasing temperature and SOH degradation Efficiency varies non-monotonically across SOC; mid-SOC operation generally minimizes losses Power Conversion System (PCS): Inverter efficiency is load-dependent — partial load (frequency regulation) can drop well below 90%; high load (energy arbitrage) approaches 97–98% Switching losses scale linearly with power; conduction losses scale quadratically — distinct mechanisms, distinct mitigation strategies Reactive power dispatch increases apparent power through the PCS without contributing to metered real energy output — a direct RTE penaltyFixed standby draw amortizes poorly over short or infrequent cycles Thermal Management: HVAC auxiliary load is a direct RTE deduction, highly climate- and architecture-dependent, and routinely underestimated in project models Liquid cooling typically carries a lower parasitic load than air-cooled equivalents while providing tighter thermal control Balance of Plant: Transformer no-load (core) losses are present even at zero throughput — continuous and unavoidable Conductor losses, site auxiliaries (BMS, EMS, SCADA, fire suppression) add a persistent baseline draw often excluded from headline RTE figures Dispatch Profile: RTE is path-dependent: same energy, different C-rate profiles → different losses Low average utilization (peakers, ancillary services) amplifies the relative weight of standby and self-discharge losses Cell-terminal, DC-meter, and AC-meter RTE can differ materially on identical hardware. This single variable explains most vendor datasheet discrepancies. A quoted AC RTE without a defined C-rate, SOC window, ambient temperature, dispatch profile, and metering boundary is a marketing number. What assumptions do you see most often buried in BESS efficiency specs? Email us at hello@camelotenergygroup.com for any questions! Raafe Khan < Back Back