How Much Electricity Does One Solar Panel Produce per Day in Los Angeles? Measured
A typical 400-watt solar panel on a Los Angeles-area roof produces about 1.56 kWh a day — roughly 569 kWh a year. That is the median of 3,608 panels on 174 home systems, each with its own microinverter. Half of all measured system-years fell between 1.43 and 1.65 kWh a day. That is about 16% less than the 1.85 kWh a day a standard solar calculator predicts for an ideal south-facing roof. Below: output by month, by panel wattage, the best and worst days, and why real roofs fall short of the model.
How much a solar panel produces each month
One 400 W panel: the typical day in each month, the range across systems, and the ideal-roof model.
| Month | Typical day | Middle half of systems | Slow day – strong day* | kWh in the month | Ideal-roof model | Measured as % of model |
|---|---|---|---|---|---|---|
| January | 1.06 | 0.92–1.21 | 0.46–1.54 | 33 | 1.42 | 74% |
| February | 1.24 | 1.12–1.40 | 0.36–1.79 | 35 | 1.60 | 78% |
| March | 1.58 | 1.48–1.68 | 0.69–2.12 | 49 | 1.85 | 85% |
| April | 1.92 | 1.79–2.03 | 0.94–2.39 | 58 | 2.02 | 95% |
| May | 1.82 | 1.71–1.93 | 0.87–2.41 | 56 | 2.01 | 90% |
| June | 1.98 | 1.82–2.11 | 1.20–2.40 | 59 | 2.08 | 95% |
| July | 2.07 | 1.96–2.22 | 1.68–2.34 | 64 | 2.25 | 92% |
| August | 1.91 | 1.79–2.05 | 1.48–2.22 | 59 | 2.26 | 84% |
| September | 1.57 | 1.43–1.69 | 0.97–1.97 | 47 | 2.09 | 75% |
| October | 1.40 | 1.20–1.59 | 0.84–1.81 | 43 | 1.77 | 79% |
| November | 1.06 | 0.90–1.22 | 0.46–1.52 | 32 | 1.54 | 69% |
| December | 0.91 | 0.77–1.05 | 0.35–1.36 | 28 | 1.32 | 69% |
| Typical day = median of the month’s average day across 351 system-months per month. *Single real days: 1 in 10 days was below the first number, 1 in 10 above the second (not adjusted for sunlight). Panels of other sizes: multiply by their wattage ÷ 400. | ||||||
The best month is July, the lowest is December, 2.3 times apart. May dips below April (1.82 vs 1.92 kWh a day), which lines up with the coastal “May Gray” season of morning low clouds; June and July then climb to the peak. Single days swing much more than monthly averages. A strong June day — the top tenth of June days — gave 2.40 kWh from a 400 W panel; a typical December day gave 0.90, and a dark, rainy December day as little as 0.35.
Do higher-wattage panels produce more?
Per panel, yes. Per watt of panel, not clearly.
| Panel class | Systems | Panels | Typical panel | kWh per panel a day | kWh per panel a year | kWh per kW a year |
|---|---|---|---|---|---|---|
| 300–379 W | 53 | 1,189 | 365 W | 1.34 | 489 | 1,382 |
| 380–419 W | 114 | 2,327 | 400 W | 1.54 | 564 | 1,423 |
| 420+ W (few systems) | 7 | 92 | 445 W | 1.72 | 627 | 1,409 |
| Panel wattage = system DC rating ÷ number of panels. The 420+ W row has only 7 systems with a complete year, so treat it as a signal; in the latest 12 months (Oct 2025–Sep 2026) it had 11. | ||||||
A higher-wattage panel makes more electricity, roughly in proportion to its rating: about 1.34 kWh a day for a typical 365 W panel against 1.54 for a 400 W panel. Per kW of panels, though, the classes were close: 1,382 and 1,423 kWh per kW a year, a 3% difference that could be chance (permutation test p = 0.07). Across all 174 systems the rank correlation between panel wattage and output per kW was 0.06. In the latest 12 months the three classes made 1,409, 1,443 and 1,430 kWh per kW. In practice: a higher-wattage panel fits more power on the same roof; it does not squeeze more out of each watt. Roof direction, tilt and shade matter more. Brands and models are compared in best solar panels for California homes.
Why real panels produce less than the calculator
Solar calculators model one ideal roof. Most real roofs are not that roof.
| Scenario | kWh a day | kWh a year |
|---|---|---|
| Model: facing south, 20° tilt, unshaded* | 1.85 | 676 |
| Model: same roof facing west | 1.62 | 592 |
| Model: same roof facing east | 1.57 | 573 |
| Measured: typical system-year | 1.56 | 569 |
| Measured: best quarter of system-years starts at | 1.65 | 604 |
| *PVWatts v8 (National Laboratory of the Rockies, formerly NREL): 400 W standard module, fixed roof mount, 14% default losses, San Fernando Valley weather file (downtown LA and the South Bay come out within 1%). Only 3% of measured system-years reached the ideal-roof figure. | ||
The calculator answer — 1.85 kWh a day for a 400 W panel, the same model our explainer how to calculate a solar panel’s output uses — assumes every panel faces due south at a 20° tilt with no shade. Measured panels made 84% of that. Where the gap comes from:
Roof direction. The same model puts a west-facing panel 12% and an east-facing one 15% below a south-facing one. Not every roof has a usable south face, and arrays are often split across several roof planes, so direction is likely part of the gap.
Winter shade. The gap is small in summer and wide in winter: May–August, measured panels made 90% of the model; November–February, 72%. A low winter sun stretches shadows from trees, chimneys and neighboring houses, and east- or west-facing panels lose more of a short day. See the winter study.
Not location. The model gives almost the same answer for the San Fernando Valley, downtown and the South Bay, so where in the LA basin a home sits does not explain the gap.
Not downtime. The model already subtracts 3% for outages. The measurements exclude outage and no-data days, so without that 3% the model would be 1.91 kWh a day and the gap slightly wider, not narrower.
Not age. Half the measured systems had been running less than 1.3 years at mid-2024. Aging is a slow effect on top of everything else: see how fast solar systems lose output.
If a quote promises close to the ideal-roof number, ask how it modeled your roof’s direction, tilt and shade.
Over a panel’s lifetime
A small signal from the oldest systems in our monitoring account.
Microinverters keep a lifetime energy counter, so each panel’s total is on record. On the 3 oldest systems in our monitoring account (first data 2013–2016, panels of 255–265 W, customers we service rather than systems we installed), the original panels have produced 3.4–5.7 MWh each over 11–14 years — 321–411 kWh per panel a year from these smaller, older panels. That is 3 systems and 71 panels: an illustration of what a panel delivers over a decade, not a benchmark.
In electric-car miles: at 30 kWh per 100 miles, a typical value on EPA fuel-economy labels, one 400 W panel’s 1.56 kWh a day covers about 5 miles of driving, around 1,900 miles a year. Check your own car’s kWh per 100 miles on fueleconomy.gov.
Methodology
How the numbers were produced.
- Data source
- Daily AC energy from Enphase monitoring for home systems in Cali Energy’s monitoring fleet. Each panel has its own microinverter, so the number of microinverters is the number of panels. These are monitoring readings, not utility meter readings.
- Systems
- 312 systems in the account; 282 kept for production after excluding customers we service but did not install, duplicate registrations, battery-only sites, systems with an obviously wrong size on record, systems expanded or repaired mid-period, and systems with no usable data. 190 have at least one complete year.
- Per panel
- System output divided by the number of panels. A “400 W panel” figure is output per kW of panels × 0.4, using only systems whose DC rating is confirmed (174 systems, 3,608 panels). 16 systems whose recorded size appears to be a default value rather than the real panel rating were left out of per-kW figures.
- Clean days
- A zero in the monitoring data usually means no data reached the portal, so zero days, the day before and after any gap, runs of identical back-filled values, days above 8 kWh per kW, and March 8, 2026 (a daylight-saving recording gap) were removed. A month counts if no more than 3 days are missing; its total is scaled to the full month.
- Typical year
- Calendar years 2023–2025 with 12 valid months (84, 156 and 151 system-years). 2023 was the least sunny year in the area since 2001, so each year is scaled to 2001–2025 average sunlight from NASA POWER: 2023 × 1.055, 2024 × 1.018, 2025 × 1.021. Unadjusted, calendar 2025 gave 1.52 kWh a day for a 400 W panel. Single-day ranges are real days, not adjusted.
- Model
- PVWatts v8 from the National Laboratory of the Rockies, formerly NREL (typical-year weather, NSRDB), 400 W standard module, fixed roof mount, 20° tilt, 14% default system losses; south-, west- and east-facing runs for the San Fernando Valley, south-facing runs for downtown LA and the South Bay.
- Statistics
- Medians and percentiles, not averages. Panel-wattage comparisons use each system’s median year; differences are tested with a permutation test and a rank correlation.
- Limits
- Not a random sample of LA roofs: these are systems we monitor, mostly installed 2022–2024. Roof direction, tilt and shade are not recorded and not adjusted for.
- Updates
- Recalculated when a calendar year closes.
Sources: PVWatts v8 calculator and API, National Laboratory of the Rockies, formerly NREL (pvwatts.nlr.gov); NASA POWER daily and monthly solar resource data (power.larc.nasa.gov); EPA fuel-economy label guide for electric vehicles (fueleconomy.gov).
Download the data
https://cali-energy.com/research/solar-panel-output-per-day-los-angeles. Aggregated data are free to use under CC BY 4.0 with a link to this page.Frequently asked questions
How much energy does a solar panel produce per day?
In Los Angeles, a typical 400 W panel produced 1.56 kWh a day over a typical year in our measurements (half of measured system-years fell between 1.43 and 1.65). Expect about 0.91 kWh a day in December and 2.07 in July.
How much does a 400 watt solar panel produce per month?
About 47 kWh in an average month in LA: roughly 28 kWh in December and 64 in July, or 569 kWh over a year.
How many watts does a solar panel produce per hour?
A 400 W panel rarely delivers its full 400 W. Averaged over LA’s 5.6 peak sun hours a day, it made about 277 watt-hours per sun-hour; spread over all 24 hours that is about 65 W.
Do higher wattage solar panels produce more electricity?
More per panel, roughly in proportion to the rating, but not clearly more per watt: panels of 300–379 W and 380–419 W made 1,382 and 1,423 kWh per kW a year, a difference that could be chance.
Why does my solar panel produce less than the calculator says?
Calculators such as PVWatts model a due-south roof at 20° with no shade (1.85 kWh a day for 400 W). Measured panels made 84% of that, and the gap is widest in winter, which points to roof direction and seasonal shade.
How much does a solar panel produce in winter in Los Angeles?
About 0.91 kWh a day from a 400 W panel in December, 1.06 in January and 1.24 in February — about 44% of a July day in December.
More research
Next steps
Panels producing less than this, or planning a system?
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.