Most states have adopted net metering laws as a requirement for electric utilities operating in the state. Net Metering is a policy whereby the utility compensates homeowners for the excess power they produce at the same rate the customer pays for the power they purchase from the grid. With net metering, customers receive roll-over credits for excess electricity produced during the peak solar producing summer or weekdays while you are in office and your home uses less electricity. These roll-over credits can then be credited towards your consumption during night when you use more or during the winter when solar panels produce less.
While utilities allow such roll-over credits to accumulate across months, most will require you to settle up your roll-over credits every 12 months. Any unused roll-over credits will likely get paid to you at a wholesale rate instead of the regular retail rate that consumers typically pay. Wholesale rates can be as low as 30%-50% of regular retail rates, which is why it is important to size your solar system correctly. Please check with your utility for details on the policy.