Tesla's solar panel really is 20.5 per cent efficient. What moved is the factory, not the datasheet.
Our record for the Tesla Solar Panel TSP-420 carries a module efficiency of 20.5 per cent, and only two of the 104 panels we score sit below it. That reads like a specification nobody has revisited. We went looking for the newer product it implied. There is not one, and the absence is the finding.
The specification is current, not stale
The median module efficiency across the 104 panels we score is 23.4 per cent. Tesla's 20.5 per cent sits in the bottom two of that set. Source: review.solar panel dataset, 19 August 2026.
Tesla's panel datasheet was reissued on 31 July 2026. It still specifies module efficiency of at least 20.3 per cent for the TSP-415 and at least 20.5 per cent for the TSP-420, a Pmax temperature coefficient of minus 0.34 per cent per degree Celsius, and a linear performance warranty of at least 98 per cent in year one falling no more than 0.45 per cent a year to at least 87.2 per cent at year 25. Source: Tesla Solar Panel datasheet, energylibrary.tesla.com, file last modified 31 July 2026.
We compared that file against the previous published revision. It is a different document with identical specifications: Tesla reset the layout and changed no number. The panel is not an old product still listed. It is the current product, and it is specified where it is specified.
A correction to our own record
Checking this turned up a defect on our side, and it is the more useful half of the exercise. The datasheet we had archived against the TSP-420 was not the TSP-420. It was the earlier Tesla Photovoltaic Module T420S, T425S and T430S, a different family: 144 cells across 2.111 square metres at 19.3 per cent, where the TSP-420 is 360 cells across 2.049 square metres at 20.5 per cent.
The California Energy Commission's equipment list separates them cleanly. The T420S family was listed on 1 July 2021. The TSP family was listed on 22 September 2025. Two product generations apart, filed under one archive. Source: California Energy Commission PV Module List, retrieved 19 August 2026.
The published figures were right, because they had been taken from the live datasheet. The stored evidence behind them was not. We have replaced the archive, corrected the record's release year from 2023 to 2025, and moved its warranty citation forward two revisions to the instrument in force, Rev 1.2 effective 2 June 2026. A citation that points at the wrong document is a defect whether or not the number above it happens to be correct.
What Tesla has reported about solar
Tesla last published a solar deployment figure in its fourth quarter 2023 shareholder letter: 41 MW for the quarter, down 59 per cent year on year, and 223 MW for the 2023 financial year, down from 348 MW in 2022. The metric does not appear in any of the ten quarterly shareholder letters published since. Source: Tesla quarterly shareholder letters, Q4 2023 through Q2 2026.
Two related changes appear in the annual filings. The balance sheet caption "Solar energy systems, net" was renamed "Energy generation and storage systems, net" in the 2025 financial year. Across the same filings the word "solar" appears 323 times for 2023, 276 times for 2024 and 40 times for 2025. Source: Tesla annual reports on Form 10-K, financial years 2023 to 2025.
Tesla has never reported solar revenue separately from storage, so the deployment series is the only quantity it published, and it stopped publishing it. Readers can draw their own conclusion about direction from those figures. We are not asserting one.
And what it has done since
The manufacturing record runs the other way over the same period. On the third quarter 2025 earnings call, on 22 October 2025, Tesla vice president Michael Snyder said the company "began production of our Tesla residential solar panel in our Buffalo factory". The 2025 annual report puts first customer deliveries in January 2026. Six models, TSP-405 through TSP-430, were listed by the California Energy Commission on 22 September 2025. Sources: Tesla Q3 2025 earnings call; Tesla Form 10-K for financial year 2025; California Energy Commission PV Module List.
In August 2026 a filing lodged with the Texas Comptroller described a vertically integrated solar cell plant in Fort Bend County with stated capital expenditure of 10.1 billion US dollars and production from the first quarter of 2029. It is a filing and a stated intention, not a commitment, and it should be read as one.
One further item sits outside all of it. A Solar Roof tile designated SR86T3R, rated 86 W, was listed by the California Energy Commission on 11 March 2026. It appears in no Tesla datasheet, no product page and no announcement we could locate, including the 742 page Solar Roof installation manual revised on 10 July 2026, which names only the 72 W and 73 W tiles. Whether it is in production or certified ahead of production is not established. Source: California Energy Commission PV Module List, retrieved 19 August 2026.
What Tesla did while it was not reporting solar deployment
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The last published deployment figure41 MW for the quarter, down 59 per cent year on year. The metric appears in none of the ten quarterly shareholder letters since.
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Six panel models certifiedTSP-405 through TSP-430 listed by the California Energy Commission, replacing a family last listed in 2021.
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Buffalo production stated on the earnings callTesla vice president Michael Snyder: the company “began production of our Tesla residential solar panel in our Buffalo factory”.
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First customer deliveriesRecorded in Tesla’s annual report for financial year 2025.
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A roof tile that appears in no Tesla documentSR86T3R, rated 86 W, listed by the California Energy Commission. Production status is not established.
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Panel datasheet reissuedA new document with the layout reset and not one specification changed.
What the datasheet cannot tell you
Tesla's panel specification places it in the lower part of our register, and the score reflects that, because the score measures the published specification. That is the instrument working. The error would be to read the same number as a statement about whether a company is developing anything, which a specification sheet is not built to answer.
On the evidence above, Tesla assembles panels of its own design and does not claim to manufacture the cells in them. Its datasheet states that the panel is "assembled in Buffalo, New York". Its August 2025 white paper argues for lower tariffs on "imported sub-components for module assembly". Where the cells come from is not published, and we are not inferring it.
For a buyer the practical position is unchanged: the panel is specified at 20.5 per cent, warranted for 25 years in the United States only, and scored on that basis. For anyone reading the register as a map of who is developing what, the panel specification is the wrong column to read, and the certification and manufacturing record is the one that moved.
Our TSP-420 record and its archived source were corrected on 19 August 2026 and the change is listed in our corrections register.
Sources and method8 references
- Tesla Solar Panel datasheet,
energylibrary.tesla.com, file last modified 31 July 2026. Retrieved and archived 19 August 2026. Source of every TSP-415 and TSP-420 electrical, thermal and warranty figure above. - Tesla Solar Panel Limited Warranty (USA), Rev 1.2, effective 2 June 2026. Names TSP-405 through TSP-430 and carries the 25 year terms and the degradation schedule.
- Tesla product certification directory,
energylibrary.tesla.com. Source for the certification list, and for the absence of IEC 61701 from it. - California Energy Commission PV Module List, retrieved 19 August 2026. Source for every listing date: the T420S family on 1 July 2021, the TSP family on 22 September 2025, and the SR86T3R tile on 11 March 2026.
- Tesla quarterly shareholder letters, fourth quarter 2023 through second quarter 2026. Source for the 41 MW quarterly and 223 MW annual deployment figures, and for the metric's absence from the ten letters since.
- Tesla annual reports on Form 10-K, financial years 2023 to 2025. Source for the balance sheet caption change, the word frequency counts, and the January 2026 first delivery date.
- Tesla third quarter 2025 earnings call, 22 October 2025. Source for the quoted statement on Buffalo production.
- Published methodology, including the evidence-state rules separating a sourced value from a reviewed absence, and the corrections register.
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