Panels needed by peak sun hours
| Sun hours (region) | System size | 400 W panels | Roof area |
|---|---|---|---|
| 3.5 h (Pacific NW) | 8.2 kW | 21 | 452 sq ft |
| 4.0 h (Northeast) | 7.2 kW | 18 | 387 sq ft |
| 4.5 h (Midwest) | 6.4 kW | 16 | 344 sq ft |
| 5.0 h (Southeast) | 5.7 kW | 15 | 322 sq ft |
| 5.5 h (Texas, Florida) | 5.2 kW | 14 | 301 sq ft |
| 6.0 h (Colorado, SoCal) | 4.8 kW | 12 | 258 sq ft |
| 6.5 h (Arizona, Nevada) | 4.4 kW | 12 | 258 sq ft |
Formula: 750 kWh ÷ 30.42 days ÷ (sun hours × 0.86). Check your exact sun hours with NREL PVWatts.
Frequently asked questions
How much does a 6.4 kW system produce per year?
About 8,999 kWh per year at 4.5 sun hours.
Do bigger panels mean fewer panels?
Yes. With 450 W panels you would need 15 instead of 16.