What size solar panel system do I actually need for my home

Your system size depends on how much electricity you actually use, not on the size of your roof. Start with your utility bill and find your annual kilowatt hour consumption. This single number tells you everything.

From usage to system size

Divide your annual kilowatt hours by the production factor for your region. Southern regions typically see factors around 1,500 to 1,600, while northern areas average 1,200 to 1,300. The result is your system size in kilowatts. A home using 12,000 kilowatt hours per year in an average region needs roughly an 8 kilowatt system.

Accounting for growth

Consider future changes: electric vehicle charging, heat pump installation, or home expansion all increase electricity needs. Many homeowners size systems 20 to 30 percent larger than current usage to accommodate this. Oversizing also provides a buffer for panel degradation over time and less than perfect weather.