Solar Size Calculator
Enter your ZIP and electricity use to estimate the solar array that would cover it: system size, panel count, roof area, production by month, cost and payback.
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How the estimate is built
- Your usage. Annual kWh if you have it. Otherwise your average bill divided by your electricity rate.
- Local sun. A typical annual yield per kW of solar for your state. You can replace it with a figure from a site-specific estimate under Advanced.
- System size. Usage times the share you want to cover, divided by yield, rounded up to whole panels.
- Money. A cost range per watt, and savings based on your rate and a range of export values. No tax credit or rebate is applied.
Before you ask for quotes
- Find twelve months of kWh on your utility account. It is the single most useful number.
- If you plan to add an EV or switch to a heat pump, size for the usage you will have, not the usage you had.
- If your heating and cooling system is old, read Should You Replace HVAC Before Solar? first. A more efficient system can mean a smaller array.
- Review the contract red flags before you sign.
See whether solar is actually the best fit for your goals.
Build My Power Plan →Common questions
Divide your annual electricity use in kWh by the annual production of one kW of solar where you live, which ranges from roughly 1,100 kWh in the cloudiest parts of the country to about 1,750 kWh in the sunniest. That gives the system size in kW. Divide by the panel wattage to get the panel count. A home using 11,000 kWh a year needs somewhere around 16 to 25 panels of 400 watts.
Not automatically. Where the utility credits exported energy at the full retail rate, covering all of your usage can make sense. Where exports earn much less, a smaller system that you mostly use yourself often pays back faster. Ask your utility how exported energy is credited before choosing a size.
Not by themselves. Standard grid-tied systems shut down when the grid fails. To use solar in an outage you need a battery or other backup equipment designed for it.
It is a first estimate based on typical production for your state, shown as a range. It does not know your roof pitch, direction or shading. Before you sign anything, get a site-specific production estimate and compare it with this one. A proposal far above this range is worth asking about.