Solar system size calculator
Size from your actual usage and your roof's sun, not the biggest system that fits.
With full net metering, about 100% usually pays best.
You need about
8.2 kW (19 panels)
to cover 100% of 10,500 kWh a year at 1,350 kWh per kW (U.S. typical; enter your location).
- Panel area
- 399 sq ft
- Roof area needed
- ~570 sq ftwith fire-code setbacks
- Yearly production
- 11,030 kWh
Show as a table
| Month | Estimated usage | Solar production |
|---|---|---|
| Jan | 945 | 919 |
| Feb | 840 | 919 |
| Mar | 770 | 919 |
| Apr | 700 | 919 |
| May | 753 | 919 |
| Jun | 945 | 919 |
| Jul | 1,103 | 919 |
| Aug | 1,103 | 919 |
| Sep | 910 | 919 |
| Oct | 753 | 919 |
| Nov | 753 | 919 |
| Dec | 928 | 919 |
| Year | 10,500 | 11,030 |
Estimated usage: 10,500 per year. Solar production: 11,030 per year
Run the full calculator to find the size with the best long-term value for your rates and price.
Bigger isn't always better
Where exported power is credited well below retail, panels beyond what you use mostly create low-value exports. Sizing to 60–90% of usage often pays best there; with full net metering, around 100% is usually right.
Questions
How many solar panels does an average house need?
A home using about 10,500 kWh a year in a sunny area (1,500 kWh per kW) needs about 7 kW, or 16 to 17 panels of 430 watts. Less sunny areas need more.