The size of your renewable energy system affects your upfront costs as well as electricity costs. PG&E gives you the tools to help you select the system that’s right for your home or business. Deciding factors include your energy-use history, the size of your roof and whether you want to offset all or only a portion of your use.
We encourage you to reduce the size and cost of the renewable system needed for your home or business by completing energy-efficiency upgrades.
Learn about the Home Energy checkup
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Estimate the size of system you need using the PG&E solar calculator.
Solar calculator tips:
- Be aware that solar generator system size is based on the amount of energy you want to offset. The recommended amount is 80 to 85 percent to maximize your savings and not lose the value of excess energy exported to the grid. The size is also calculated based on your energy use history or average bill.
- View the estimated system details and costs associated with different financing options that are displayed.
- Note the recommended photovoltaic (PV) solar system size, which refers to the number of panels and energy that the PV solar panels produce. This is the estimate needed for your home. The average size of a residential system is between four and five kilowatts (kW). If the system size proposed by your contractor differs greatly from this, have a conversation with your contractor about why.
- The amount of physical space a solar panel system requires is also important. As a general rule, you need approximately 100 square feet of roof space for each kW installed.
Note: There is no financial benefit to installing a system larger than your home needs. Compensation for excess generation through Net Surplus Compensation (NSC) is set by the California Public Utilities Commission (CPUC) at roughly two to four cents per kWh. This amount does not justify the cost of an oversized system.