Some states and utilities allow for “net metering.” This means that your solar panels produce electricity during the day to power your home, and any excess produced is sold back to your utility for credits. Then, in the evening, you pull electricity from the grid but don't get charged because of the credit.

If you live in a state that does not allow for net metering, it makes most economic sense to size your solar array to match the electricity you use throughout the day when the sun is shining. This is typically about ⅓ of your electrical usage. 

That way, you power your home with free solar electricity while the sun is shining, and pull from the grid when it is not.

Alternatively, you can size your panels to meet 100% of your electrical needs and use a battery to store the excess power to use at night. This increases the cost up front, but usually pays back in operating savings.

A solar installer will be able to give you specifics of the right size system to maximize savings based on your particular house and utility programs.

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