Ethan Miller, TXSES Intern, and Larry Howe, Solar and Climate Solutions Advocate
It’s not hard to find estimates for utility-scale solar capacity in Texas; ERCOT regularly releases that information.1 What has been harder to find are estimates of distributed (rooftop) solar. Up until now, getting a realistic idea of how many buildings had rooftop systems was practically guesswork.
There are a few reasons for this:
- Distributed solar can be metered or unmetered (and there are multiple metering techniques);
- Distributed solar can be placed on residential, commercial and industrial buildings;
- Reporting varies by utility provider (municipal, electric cooperative, competitive market, investor-owned); and
- There is no singular reporting agency/organization.
Through the Texas Solar Energy Society, I connected with Larry Howe, who in his spare time was working on such an estimate. After meeting with him and reviewing his methodology and data sources, we devised a method to determine the volume of rooftop installations in the state.
For our analysis, we relied on scraping data from two main sources: the Electric Reliability Council of Texas (ERCOT) and the Energy Information Administration (EIA). For the latest numbers, we used ERCOT’s Load Profiling Profile Type Counts (last updated October 3, 2023), EIA’s Annual Electric Power Industry Report, Form EIA-861 (both for net-metered and non-net-metered, updated 2022 and 2021 for Austin Energy), and EIA’s Form EIA-861M (monthly, updated July 2023). [2] [3] [4]
Since ERCOT’s Load Profiles tracked the amount of distributed energy only in competitive (deregulated) regions of the state, we used the EIA-861 and EIA-861M to get installation counts for residential and commercial buildings in municipal and cooperative utilities. The biggest challenge, however, was that the EIA-861 only reported installation count for net-metered projects. The EIA-861M counts customers for residential and commercial. ERCOT had only an idea of how much MW capacity the non-net-metered generators were producing. To resolve this, I used Google’s Project Sunroof per roof system capacity of 12.3 kW DC.[5] It’s important to note that Project Sunroof is a tool designed to estimate maximum distributed capacity in the state. Because that 12.3 kW DC is a much larger system size than is typical, we believe our final estimate is likely conservative. Lastly, EIA data often included private utilities as well (those already reported in ERCOT numbers). We removed them to ensure we weren’t double-counting.
It’s important to disclose the limitations of our estimates.
As previously noted, we had to rely on Project Sunroof’s estimate of average project capacity. Additionally, not all data are dated for 2022. Because Austin Energy’s net-metered count didn’t appear in EIA’s 2022 data, (possibly because of the city’s use of Value-of-Solar in place of net-metering), we relied on data from 2021 which may be marginally outdated. Lastly, the data are incomplete. EIA doesn’t seem to report numbers for all municipal or cooperative utilities in the state, and ERCOT’s numbers are restricted to ERCOT’s area, so those serviced by the Western Electricity Coordinating Council, Southwest Power Pool, or Southeastern Electric Reliability Council have not been included.
With clean data, we tallied all the installations. As of today (October 19, 2023), we estimate the total number of rooftop solar installations in Texas to be ~294,817.86. To give a better idea of the scale, take the U.S. Census Bureau’s figure of 12,136,678 housing units in the state (as of 2022).[6] Using the numbers for residential installations only, it looks like 2.39% of all Texas residences have rooftop solar installed. For all buildings in the state, it is 2.31%. While that number might seem small, it’s impressive progress for a fledgling industry that didn’t even appear in the Solar Energy Industries Association count of annual solar installations until 2013.[7]
One decade in, we’ve made significant progress but there’s much more to do to enact sound distributed solar policies that will build a well-trained distributed solar energy workforce and mitigate impending grid disruptions and failures. Our newest initiative, Infinite Power: Take Your Share of the Texas Sun, is an ambitious statewide educational campaign intended to double the amount of distributed solar in Texas by 2030. Through a collaborative process with industry groups, business members, and solar homeowners alike, TXSES will lead that charge, intensifying consumer education and heightening awareness that distributed solar will support ambitious clean energy and carbon reduction goals, enhance the resilience and reliability of the electric grid and build a diverse, equitable, well-trained distributed solar workforce.
If you’re interested in getting involved with similar research or would like to access our data, please reach out to Ethan Miller (ethan@txses.org)
Sources:
“Annual Electric Power Industry Report, Form EIA-861 Detailed Data Files.” Electricity, 2022. https://www.eia.gov/electricity/data/eia861/.
“Estimated Rooftop Solar Potential of Texas.” Project Sunroof, June 2019. https://sunroof.withgoogle.com/data-explorer/place/ChIJSTKCCzZwQIYRPN4IGI8c6xY/.
“Profile Type Counts.” Load Profiling, October 3, 2023. https://www.ercot.com/mktinfo/loadprofile.
“Texas Solar.” Solar Energy Industries Association, 2023. https://www.seia.org/state-solar-policy/texas-solar.
“Texas.” QuickFacts, July 1, 2022. https://www.census.gov/quickfacts/fact/table/TX,US/EDU685221.
Vegas, Pablo, et al. “September 2023 Fact Sheet.” Electric Reliability Council of Texas, September 2023. https://www.ercot.com/files/docs/2022/02/08/ERCOT_Fact_Sheet.pdf.
[1] Vegas 2023.
[2] “Profile Type Counts” 2023.
[3] “Form EIA-861” 2022.
[4] “Form EIA-861M” 2023.
[5] Project Sunroof 2019.
[6] QuickFacts 2022.
[7] Solar Energy Industries Association 2023.