Frequently Asked Questions

The amount of roof space needed is based on the size, or generating capacity, of the solar energy system. Residential solar energy systems can vary in size from 50 square feet to 1,000 square feet. A rule of thumb is that a square foot of PV module area produces 10 watts (W) of power in bright sunlight. For example, a 2,000 W system would require about 200 square feet of roof area.

Several factors will influence the size of the solar electric generating system. The first step in determining the appropriate size is to conduct a free energy efficiency audit and implement measures to reduce the amount of electricity you need. The second step is to review your previous 12 months of electricity usage. Typically,  solar installers and contractors will be able to help you with these steps.

For CSI systems the average residential solar energy system size in our service territory is about 5 kilowatts (kW), and the average non-residential solar system size is 262 kW. The CSI program allows customers to size a solar system up to their previous 12 months electrical requirements, but in most cases homeowners only need to size a system to avoid the upper three billing tiers.

In California, a PV system will produce the most electricity in spring through fall when sunlight hours are the longest and the sun is positioned higher in the sky. A 1-kW system can produce from 1,400 kilowatt-hours (kWh) to 2,000 kWh per year depending on the location within the state. Generally, a PV system in Southern California will produce more electricity than one in Northern California.

A kW is a basic unit of measure of real electric power or a rate of doing work. A kW is 1,000 W.

A kWh is a basic unit of energy consumption. For example, ten 100W light bulbs burning for one hour will consume 1,000 W-hours, or 1 kWh of electricity.

A. The cost varies depending on many factors, including the solar energy system’s size, equipment options and labor costs. Typically, the installed costs are determined based on the size of the system’s output. The “cost per watt” ($/W) is often used for comparing systems of different sizes.

It is difficult to predict how much an individual system will cost. Visit California Solar Statistics to find out the current average $/W for systems installed through the CSI program. Visit the U.S. Solar Photovoltaic System Cost Benchmark provided by the National Renewable Energy Laboratory (NREL).

The California Solar Rights Act, enacted in 1978, limits the ability of covenants, conditions and restrictions (typically enforced by homeowners associations) and local governments to restrict solar installations. Get more information on the California Solar Rights Act.

Yes. PV output can be impacted by dirt accumulation. The frequency of cleaning depends on the location. For example, locations closer to freeways or industrial facilities, or in high-wind areas are likely to accumulate dirt more rapidly and should be cleaned more frequently.

No, a solar generation system operates automatically, and shuts itself on and off automatically.

If a power outage occurs, your solar energy system is designed to immediately shutdown for safety reasons. A grid-tied solar electric system does not provide power during outages unless it includes a battery storage system. Your power will be reinstated moments after grid power is restored; however, you may need to manually reset your solar system’s inverter back to service after your power is reinstated (most auto reset after power is restored). 

For additional information on “going solar”, visit Go Solar California.