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Residential Solar PV Systems

System Sizing

A residential solar PV system is sized based on annual electricity consumption and local solar resource. A home using 10,000 kWh per year in a location receiving 4.5 peak sun hours per day needs approximately 7.2 kW of panels: 10,000 kWh ÷ 365 days ÷ 4.5 hours ÷ 0.85 system efficiency = 7.2 kW. At current panel efficiency, this requires approximately 18 panels of 400 watts each, covering about 360 square feet of south-facing roof. The installed cost in 2025 averages $2.80-3.50 per watt before incentives, so a 7.2 kW system costs $20,000-25,000. The 30 percent federal tax credit reduces this to $14,000-17,500, with some states offering additional incentives.

Residential Solar PV Systems

System Sizing

A residential solar PV system is sized based on annual electricity consumption and local solar resource. A home using 10,000 kWh per year in a location receiving 4.5 peak sun hours per day needs approximately 7.2 kW of panels: 10,000 kWh ÷ 365 days ÷ 4.5 hours ÷ 0.85 system efficiency = 7.2 kW. At current panel efficiency, this requires approximately 18 panels of 400 watts each, covering about 360 square feet of south-facing roof. The installed cost in 2025 averages $2.80-3.50 per watt before incentives, so a 7.2 kW system costs $20,000-25,000. The 30 percent federal tax credit reduces this to $14,000-17,500, with some states offering additional incentives.