Did Wildfire Smoke Cut Rooftop Solar Output in LA? The January 2025 Fires and Other Smoke Days, Measured
Yes, for a few days. On January 8, 2025, as smoke from the Eaton and Palisades fires spread over the Los Angeles basin, rooftop systems there made a median 64% of their usual output for the sunlight available; in the San Fernando Valley, 88%. By January 12 the fleet was back to 100%. The ash that followed cost little at first; the first soaking rain since spring 2024, on January 26–27, then lifted the same roofs to 104–109% of their pre-fire level by washing off ash and months of dust. Across every clear day since 2022, each 0.1 of aerosol optical depth — the standard measure of haze, smoke and dust — cost about 2% of output.
Smoke cuts solar output the way a thin cloud does: fine particles scatter and absorb sunlight before it reaches the panels.
January 2025, day by day
Output per unit of sunlight on clear days, as a share of each system’s clear days from December 10 to January 6.
| Date | All systems | LA basin | San Fernando Valley | Systems below 70% | Systems at zero | Aerosol over the basin (CAMS) |
|---|---|---|---|---|---|---|
| January 5 | 100% | 100% | 99% | 0% | 0 of 153 | 0.07 |
| January 7 | 87% | 88% | 78% | 16% | 0 of 152 | 0.03 |
| January 8 | 84% | 64% | 88% | 28% | 12 of 152 | 0.11 |
| January 9 | 95% | 80% | 98% | 11% | 8 of 152 | 0.51 |
| January 10 | 98% | 92% | 100% | 1% | 4 of 153 | 0.46 |
| January 11 | 99% | 95% | 101% | 1% | 0 of 153 | 0.33 |
| January 12 | 100% | 98% | 102% | 1% | 0 of 154 | 0.21 |
| January 13 | 100% | 97% | 101% | 2% | 2 of 155 | 0.07 |
| January 14 | 99% | 98% | 100% | 1% | 1 of 153 | 0.06 |
| January 15 | 99% | 97% | 100% | 1% | 0 of 153 | 0.06 |
| January 16 | 97% | 97% | 97% | 0% | 0 of 153 | 0.09 |
| 100% = each system’s own clear days from December 10, 2024 to January 6, 2025. Systems at zero are counted among systems that produced in the week before and after; they are left out of the medians. | ||||||
January 7 was the day of the windstorm and the first fire. Valley systems dropped to 78% and basin systems to 88%. That day’s loss could be blowing dust, the first smoke or power cuts for part of the day; daily totals cannot tell them apart. January 8 is clearer: the loss moved to the basin, where systems made 64% and 28% of all systems were below 70%, while the few Santa Clarita systems made 97%. The basin was still at 80% on January 9 and 92% on January 10. The CAMS model registered the smoke over the basin only from January 9 (aerosol 0.51, against 0.11 the day before), a reminder that a global model can miss a fresh local plume.
Some systems went dark for a different reason. 12 of 152 made nothing at all on January 8, 8 on January 9 and 4 on January 10. A grid-tied inverter must switch off when the grid goes down, so a zero during a fire is a power cut, not smoke; shorter cuts of a few hours look like a weak day in daily totals and may account for part of the losses above.
https://cali-energy.com/research/wildfire-smoke-solar-output-los-angeles. Aggregated data are free to use under CC BY 4.0 with a link to this page.Ash, and what the rain showed
After the smoke cleared, output for the sunlight stayed at 93–100% of the pre-fire level through January 24, drifting down as ash and dust settled. The first soaking rain since spring 2024, on January 26–27, changed that: on the next clear days the same systems made 104% (January 28), 109% (February 9) of their pre-fire level. The panels had been carrying months of dry-season dust before the fires, and the ash added to it. How much a first rain gives back in a normal year, and how this one compared, is measured in how much output dirty solar panels lose.
September 2024: smoke on top of heat
| Date | Systems | Per unit of sunlight | Aerosol, Valley (CAMS) | Aerosol, basin (CAMS) | Daily high, Valley (ERA5) |
|---|---|---|---|---|---|
| September 7 | 136 | −1.5% | 0.28 | 0.41 | 106 °F |
| September 9 | 149 | +0.1% | 0.06 | 0.10 | 106 °F |
| September 10 | 149 | −2.0% | 0.04 | 0.05 | 97 °F |
| September 11 | 149 | +4.2% | 0.12 | 0.21 | 82 °F |
| September 12 | 142 | −5.1% | 0.16 | 0.32 | 80 °F |
| September 13 | 149 | −4.5% | 0.23 | 0.55 | 81 °F |
| Clear days only, against the same system’s clean-air clear days within 15 days and within 10 °F of the day’s high. | |||||
The fires of early September 2024 burned during a heat wave, so the comparison here holds temperature roughly constant. The losses were smaller than in January, about 5% on the smokiest days over the basin; those fires were farther from the homes we monitor. What the heat itself cost is in how much heat waves cut output.
Every hazy day since 2022
All clear days, August 2022 to October 2026, by the day’s aerosol optical depth (CAMS, 550 nm).
| Aerosol optical depth | Systems | System-days | Per unit of sunlight | Middle half of systems |
|---|---|---|---|---|
| under 0.15 | 219 | 82,727 | −0.5% | −0.8% to −0.3% |
| 0.15–0.19 | 215 | 18,278 | −1.9% | −3.1% to −1.0% |
| 0.20–0.24 | 215 | 6,514 | −1.8% | −3.1% to −0.8% |
| 0.25–0.29 | 177 | 1,197 | −3.1% | −7.1% to −1.6% |
| 0.30–0.39 | 179 | 582 | −4.4% | −6.8% to −3.1% |
| 0.40 or more | 70 | 262 | −8.9% | −11.6% to −6.0% |
| A typical day is about 0.10 over the Valley and 0.15 over the basin; 0.3 is visible haze; the haziest days here reached about 0.7. The CAMS grid is coarse, so the Valley and Santa Clarita share one value. | ||||
The relationship is steady. Days with aerosol of 0.15–0.24 cost about 2%, 0.30–0.39 about 4%, and the haziest days, 0.40 or more, 9%; all 70 systems with such days were in the basin. Fitted system by system, each 0.1 of optical depth cost 1.9% (middle half 1.3–2.6%). Most of these days are ordinary urban haze and spring dust rather than smoke, and together they cost the median system about 0.4% of a year’s output, more in the basin.
What it means for a homeowner
A smoky day can take a third off a system’s output, and that is the air, not the equipment. If the whole neighborhood is hazy and your production is down for a day or two, wait for it to clear; the daily fleet index shows whether other roofs dipped the same day. A day of zero during a fire or windstorm usually means the grid was cut, and the system will restart when power returns; why it has to shut off is explained in what a solar inverter does. Ash on the panels costs little at first and washes off with the first soaking rain; for the roof itself, see roof damage after wildfire smoke and ash.
Methodology
- Systems
- 219 Enphase-monitored rooftop systems in Los Angeles and Ventura counties with a verified DC rating; daily production checked as in the production benchmark; days of zero excluded from the medians.
- Sunlight
- ERA5 reanalysis (Open-Meteo) at four area points. ERA5 computes sunlight with average aerosol rather than the day’s actual smoke, so output divided by ERA5 sunlight falls on smoky days. A clear day has at least 90% of the point’s clear-sky sunlight.
- Aerosol
- CAMS (Open-Meteo Air Quality) daily mean aerosol optical depth at 550 nm, from August 4, 2022. The model is coarse and can lag a fresh local plume.
- January 2025
- Each system’s clear days from December 10, 2024 to January 6, 2025 set its 100%. A system counts as at zero when it made nothing that day but produced on at least four of the seven days before and after.
- All hazy days
- Each clear day against the same system’s clear days with aerosol under 0.15, within 15 days of the same year and within 10 °F of the day’s high (at least three).
- Limits
- Daily totals only: hours of power cuts cannot be separated from smoke.
Frequently asked questions
Did the January 2025 fires reduce solar output in Los Angeles?
Yes, for a few days. On January 8, 2025, systems in the LA basin made a median 64% of their pre-fire output for the sunlight available and San Fernando Valley systems 88%. By January 12 the fleet was at 100%.
How much does wildfire smoke reduce solar panel output?
It depends on how thick it is. Across clear days since 2022, each 0.1 of aerosol optical depth cost about 2%, and the haziest days 9%. Under the thick smoke of January 8, 2025 basin systems lost about 36%.
Why did my solar system make zero during the fire?
Most likely the grid was down. 12 of 152 systems in our fleet made nothing on January 8, 2025. A grid-tied system must switch off when the grid fails and restarts when power returns.
Does ash on solar panels reduce output?
A little. Output stayed at 93–100% of the pre-fire level until the late-January storm, which lifted it above the pre-fire level by washing off ash and dust together.
How much does haze cost over a year?
About 0.4% of a year’s output for the median system in our fleet, and around 1% for the haziest quarter, mostly in the LA basin.
More research
Next steps
Output still low after the smoke cleared?
Prepared by Cali Energy, October 15, 2026. Figures describe systems in our monitoring fleet and are not a guarantee of what any specific roof will produce; orientation, tilt, shade, equipment and weather change results. Not engineering, financial or utility advice. See our Content Disclaimer.