Original modeled solar data
How many solar panels for 1,000 kWh per month?
A home using 1,000 kWh per month needs about 18–35 solar panels when using 400-watt panels, 20% system losses and a 100% electricity offset. At five peak sun hours per day, the estimate is 21 panels, or about an 8.4 kW system.
Published August 6, 2026
Panel count for 1,000 kWh per month by peak sun hours
This is original modeled data from Watt My Roof's calculator assumptions. It is not a claim about national averages, utility bills or roof fit. It isolates one question: if the electricity target is 1,000 kWh per month, how many 400-watt panels are needed at different sunlight levels?
| Peak sun hours/day | Estimated 400 W panels | System size | Annual panel output used |
|---|---|---|---|
| 3.0 | 35 panels | 14.0 kW | 350 kWh/panel/year |
| 3.5 | 30 panels | 12.0 kW | 409 kWh/panel/year |
| 4.0 | 26 panels | 10.4 kW | 467 kWh/panel/year |
| 4.5 | 23 panels | 9.2 kW | 526 kWh/panel/year |
| 5.0 | 21 panels | 8.4 kW | 584 kWh/panel/year |
| 5.5 | 19 panels | 7.6 kW | 642 kWh/panel/year |
| 6.0 | 18 panels | 7.2 kW | 701 kWh/panel/year |
Formula assumptions: 400-watt panels, 20% total system losses, 100% offset and no battery charging load.
The formula used for this data
The model first turns monthly electricity use into an annual target. Then it estimates how much electricity one panel produces in a year and rounds the required panel count up.
Why 1,000 kWh can mean 18 panels in one place and 35 in another
A panel does not create the same annual electricity everywhere. With the same 400-watt panel and the same 20% loss factor, three peak sun hours produces about 350 kWh per panel per year. Six peak sun hours produces about 701 kWh per panel per year. Same panel. Same formula. Very different output.
Watt My Roof shows the assumptions instead of hiding the math behind a lead form. The tradeoff is that this is a planning calculator, not a site survey, engineering design, savings guarantee or solar quote.
Modeled panel counts for 500–1,500 kWh per month
The broader table below is useful for comparison and for AI-answer citation. It uses the same assumptions as the 1,000 kWh table: 400-watt panels, a 0.80 performance factor and 100% electricity offset.
| Monthly use | 3.0 sun hrs | 3.5 sun hrs | 4.0 sun hrs | 4.5 sun hrs | 5.0 sun hrs | 5.5 sun hrs | 6.0 sun hrs |
|---|---|---|---|---|---|---|---|
| 500 kWh | 18 | 15 | 13 | 12 | 11 | 10 | 9 |
| 750 kWh | 26 | 23 | 20 | 18 | 16 | 15 | 13 |
| 1,000 kWh | 35 | 30 | 26 | 23 | 21 | 19 | 18 |
| 1,250 kWh | 43 | 37 | 33 | 29 | 26 | 24 | 22 |
| 1,500 kWh | 52 | 45 | 39 | 35 | 31 | 29 | 26 |
Download the modeled data as CSV: solar-panels-1000-kwh-by-sun-hours.csv.
What can make your real number different?
- Actual panel wattage: 450-watt or 500-watt panels can lower the count, while older 300-watt panels raise it.
- Shade and roof orientation: usable production can drop even when the regional sun-hour estimate looks good.
- Utility rules: interconnection limits, net-metering rules and export rates can change what size system makes sense.
- Battery goals: backup power can change system design, especially if you want to recharge batteries during outages.
- Seasonality: a single 1,000 kWh summer bill is not the same as a twelve-month average of 1,000 kWh.
FAQ
How many solar panels do I need for 1,000 kWh per month?
Using 400-watt panels, 20% system losses and 100% electricity offset, a home using 1,000 kWh per month needs about 18–35 solar panels depending on local peak sun hours. At five peak sun hours per day, the estimate is 21 panels.
Is 1,000 kWh per month a lot for a home?
It is a meaningful electricity load, but not unusual for larger homes, all-electric homes, homes with central air conditioning, electric water heating, a pool pump or EV charging. The better question is whether 1,000 kWh is your twelve-month average or only a seasonal high.
Can a 10 kW solar system make 1,000 kWh per month?
Often, but not everywhere. Under the assumptions on this page, a 10 kW system with five peak sun hours produces about 1,217 kWh per month before site-specific limits. In a lower-sun or shaded location, production can be much lower.
Why does the panel count change so much by location?
The panel count changes because each panel produces more annual electricity in a higher-sun location. A 400-watt panel at six peak sun hours produces about twice as much annual electricity as the same panel at three peak sun hours, before other site conditions are considered.
The panel counts on this page are modeled outputs from Watt My Roof's published assumptions: monthly electricity use, panel wattage, peak sun hours, a 20% loss allowance and desired electricity offset. For the complete calculation context, see the methodology page and the solar panel calculation guide.