Kilowatt (kW)

A kilowatt (kW) equals 1,000 watts and is the standard unit for measuring the size and power output of residential solar systems.

When solar installers describe a system as “8 kW,” they mean it can produce 8,000 watts of electricity under peak conditions. Typical residential solar systems in the United States range from 5 kW to 12 kW, depending on the household’s electricity usage, available roof space, and budget. A 5 kW system might suit a small home with modest energy needs, while a larger 10–12 kW system can power a home with high electricity consumption or an electric vehicle. Solar system costs are commonly quoted in dollars per kilowatt — for example, $2,770/kW is equivalent to $2.77 per watt. The system size you need depends on your annual kilowatt-hour (kWh) consumption, your roof’s sun exposure, and your local electricity rates.