Solar panels needed for 300 kWh per month
7 panels
of 400 W (2.8 kW) cover 300 kWh/month at 4.5 peak sun hours · about $7,778 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 | 4.2 kW | 11 | 236 sq ft |
| 3.5 h | 3.6 kW | 9 | 194 sq ft |
| 4 h | 3.1 kW | 8 | 172 sq ft |
| 4.5 h | 2.8 kW | 7 | 150 sq ft |
| 5 h | 2.5 kW | 7 | 150 sq ft |
| 5.5 h | 2.3 kW | 6 | 129 sq ft |
| 6 h | 2.1 kW | 6 | 129 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 300 kWh a month?
About 7 panels of 400 W (2.8 kW) with 4.5 peak sun hours; 6 in a 6-hour sunny climate and 9 at 3.5 hours.
What does a 2.8 kW system cost?
At a typical $2.50-$3.20 per watt installed: $6,944-$8,889 before incentives.