Estimate how many solar panels you need based on energy usage, sun hours, and panel wattage.
| Monthly Usage | System Size | Panels (400W) |
|---|---|---|
| 500 kWh | 4 kW | 10 |
| 900 kWh | 7.5 kW | 19 |
| 1500 kWh | 12.5 kW | 32 |
| 2000 kWh | 17 kW | 42 |
The Federal Investment Tax Credit (ITC) lets homeowners deduct 30% of solar installation costs from federal taxes through 2032. It steps down to 26% in 2033.
Each 400W panel occupies about 20 sq ft. A 20-panel system needs roughly 400 sq ft of unshaded south-facing roof.
Enter your monthly electricity usage (kWh), location, roof angle, and available roof area. The calculator estimates the system size, number of panels, costs, and savings.
System Size (kW) = Annual kWh / (Peak Sun Hours Γ 365 Γ 0.80 efficiency). Panels = System kW / Panel Wattage. Typical: 400W panels, 4-6 peak sun hours (varies by location).
Monthly usage 1,000 kWh in Phoenix (6 sun hours): System = 12,000 / (6 Γ 365 Γ 0.8) = 6.85 kW. That is 18 panels (375W each). Cost: ~$14,000-18,000 before tax credit.
The federal solar tax credit (ITC) covers 30% of costs through 2032. South-facing roofs at 30-45Β° angle are optimal. Panels last 25-30 years with ~0.5% annual degradation. Compare at least 3 installer quotes.