Solar panels needed for 800 kWh per month
19 panels
of 400 W (7.4 kW) cover 800 kWh/month at 4.5 peak sun hours · about $20,741 before the 30% credit at $2.80/W
System size by peak sun hours
| Peak sun hours | System size | 400 W panels | Roof area |
|---|---|---|---|
| 3 h | 11.1 kW | 28 | 602 sq ft |
| 3.5 h | 9.5 kW | 24 | 516 sq ft |
| 4 h | 8.3 kW | 21 | 452 sq ft |
| 4.5 h | 7.4 kW | 19 | 408 sq ft |
| 5 h | 6.7 kW | 17 | 366 sq ft |
| 5.5 h | 6.1 kW | 16 | 344 sq ft |
| 6 h | 5.6 kW | 14 | 301 sq ft |
kW = monthly kWh ÷ 30 ÷ sun hours ÷ 0.8 (inverter, wiring, soiling and temperature losses). Southwest US ~5.5-6.5 h, Midwest/Northeast ~3.5-4.5 h.
FAQ
How many solar panels for 800 kWh a month?
About 19 panels of 400 W (7.4 kW) with 4.5 peak sun hours; 14 in a 6-hour sunny climate and 24 at 3.5 hours.
What does a 7.4 kW system cost?
At a typical $2.50-$3.20 per watt installed: $18,519-$23,704 before incentives.