To cover 2,000 kWh a month (24,000 kWh a year) at a typical U.S. location (median state, 1,340 kWh per kW a year), you need about 18 kW — 41 × 440-W panels on roughly 1,103 sq ft of roof.
| Panel | Panels | System | Roof area |
|---|---|---|---|
| 400 W | 45 | 18 kW | 1,101 sq ft |
| 420 W | 43 | 18.06 kW | 1,105 sq ft |
| 440 W | 41 | 18.04 kW | 1,103 sq ft |
| 460 W | 39 | 17.94 kW | 1,097 sq ft |
| State | kWh per kW | System kW | Panels | Roof sq ft |
|---|---|---|---|---|
| Arizona | 1,755 | 14.1 | 32 | 861 |
| California | 1,677 | 14.5 | 33 | 888 |
| Texas | 1,421 | 17.2 | 39 | 1,049 |
| Florida | 1,455 | 16.7 | 38 | 1,023 |
| North Carolina | 1,446 | 16.7 | 38 | 1,023 |
| New York | 1,291 | 18.9 | 43 | 1,157 |
| Massachusetts | 1,302 | 18.5 | 42 | 1,130 |
| Illinois | 1,265 | 19.4 | 44 | 1,184 |
| Washington | 1,077 | 22.4 | 51 | 1,372 |
Location changes the answer by about 59%: the same 2,000 kWh takes 32 panels in Arizona but 51 in Washington. At 18 kW this is bigger than the 12 kW median system quoted on EnergySage in 2026.
Sun-hours check: 2,000 kWh a month is 65.8 kWh a day. With 4.93 peak sun hours and the 0.74 derate factor implied by the modeled yield (losses, inverter, heat), 65.8 ÷ (4.93 × 0.74) = 17.91 kW — the same answer.
Where exports earn less than retail (California, Arizona, Utah, Georgia and others), many installers size to about 70% of use: 12.8 kW here. Run the numbers in the solar payback calculator.
The full method, material data and tips are on the main solar panel calculator page.