Solar panels needed for 1,200 kWh per month
28 panels
of 400 W (11.1 kW) cover 1,200 kWh/month at 4.5 peak sun hours · about $31,111 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 | 16.7 kW | 42 | 903 sq ft |
| 3.5 h | 14.3 kW | 36 | 774 sq ft |
| 4 h | 12.5 kW | 32 | 688 sq ft |
| 4.5 h | 11.1 kW | 28 | 602 sq ft |
| 5 h | 10.0 kW | 25 | 538 sq ft |
| 5.5 h | 9.1 kW | 23 | 494 sq ft |
| 6 h | 8.3 kW | 21 | 452 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 1,200 kWh a month?
About 28 panels of 400 W (11.1 kW) with 4.5 peak sun hours; 21 in a 6-hour sunny climate and 36 at 3.5 hours.
What does a 11.1 kW system cost?
At a typical $2.50-$3.20 per watt installed: $27,778-$35,556 before incentives.