All Dominion’s Solar Plants Are Failing Their Energy Promises
The average number of minutes Dominion customers lost power in 2023, compared to various peer utilities, including Appalachian Power and PEPCO. Source: SCC testimony
by Steve Haner
Every solar facility in Dominion Energy Virginia’s expanding fleet of silicone panels is failing to perform up to its initial energy promises, according to a State Corporation Commission staff analysis. In many cases the shortfalls are dramatic.
The data popped up in testimony that is part of the utility’s application for a base rate increase. There are dozens of issues in that pending case, set for a public hearing September 2. One issue is whether the company has earned a bonus on its profit margin due to good performance, and the SCC staff has recommended it not get it, in part because of the poor solar performance.
Neil Joshipura of the SCC staff wrote in his testimony:
Based on the data provided, all of the Company’s solar facilities had average actual capacity factors that were lower than their respective design capacity factors. The absolute differences between the design and actual values ranged from 1.2 to 10.3 percentage points, with an average difference of 4.3 percentage points. Piney Creek Solar had the largest absolute difference; its design capacity factor was 22.6 percent, while its actual capacity factor for 2024, the only year with available data, was 12.3 percent. This represents a 48 percent shortfall relative to the design value.
Capacity factor is a measure of how often a power plant produces electricity, and it is never 100% over time. When the plant is advertised as producing 100 megawatts or 500 or more, that is the nameplate value at 100%. That must then be multiplied by the capacity factor, and in the case of solar fields here in Virginia, that capacity factor is a very low number, usually below 25%.
Joshipura’s testimony included a table that listed the “capacity factor” for 25 Dominion solar plants for 2023 and 2024, the performance period being reviewed in the rate case. It then compared that to the amount of production the utility projected when the facilities were designed and installed. The nominal discrepancy was more than four percentage points, but that is misleading. Many produce 20% less electricity than we ratepayers were promised.
The design capacity factor of 25 Dominion solar plants compared to actual performance, 2023-2024. Source: SCC testimony.
The SCC staff should have taken an extra step and included the faceplate value of the plant. Then it could do some sums and calculate how much actual electricity was promised but not produced, for each individual location and then for the whole fleet. That is important information. The fleet is growing. Under the mandates of the Virginia Clean Economy Act, Dominion has only started to build the hundreds of square miles of solar fields it will need to keep the lights on (and only just some of the time.)
Dominion blamed the shortfalls on maintenance issues, usually failures of the inverters, and “lower than expected insolation.” That means the sun didn’t shine. Funny how that works. The company had better luck with its two existing offshore wind turbines, with their 46% reported capacity factors, meaning a bit more wind hit than expected.
The next time a Dominion presser in the newspaper brags about a 400-megawatt solar plant coming to cover a denuded forest in your county, remember that 400 MW must be discounted by the design capacity factor (suddenly it only 100-110 MW) and then further eroded by the historical production at the company’s other plants. In the end 400MW is only about 80-90 MW. It is cheap when it works, it just doesn’t work very often.
In rebuttal testimony also filed with the SCC in the case file, Dominion doesn’t dispute Joshipura’s numbers and really doesn’t dispute his recommendation that there be more attention to preventive maintenance. The company’s VP for generation merely responds that discussion belongs in another review, not this general rate case.
Joshipura’s testimony also covered the company’s record of electricity outages during the period which he stated has been showing improvement. There are two common measures. SAIDI tracks the duration of outages and SAIFI the frequency. For 2023, Dominion’s average annual outage for customers was 123 minutes per year and they lost power an average of 1.165 times per year. Individual customer experience will vary widely. Whether those are means or medians isn’t noted that I saw. One of the tables is at the top of this report and the other below.
The average number of power outages a Dominion customer experienced in 2023 compared with various peer utilities. Source: SCC testimony.
Republished with permission from Bacon’s Rebellion.
