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California Solar Initiative FAQs

Solar FAQ

What is a solar electric or photovoltaic (PV) system and how does it work?

Solar electric or PV technology uses the sun’s energy to make electricity. When sunlight strikes an array of solar panels, electrons are freed by the interaction of sunlight with semiconductor materials (typically silicon). The movement of electrons creates current, thus creating direct current (DC) power.

DC is the only type of current produced by solar cells. Appliances and machinery, however, operate on alternating current (AC) as supplied by your utility. The DC energy produced by the panels is fed into an inverter that transforms the DC power into AC power, which then feeds into the main electrical panel that powers your house or business.

A bi-directional meter connected to the electrical panel measures the amount of electricity you purchase from our grid and the excess electricity produced by your solar system and fed back to our grid for net energy metering.

Is my home or business a good place for a PV system?

First consider how much sunlight your property receives. Your property should have a clear, unobstructed access to the sun for most of the day, and throughout the year.

In California, the sun is in the southern half of the sky and produces more PV electricity than in the northern part. Because shading will reduce the amount of electricity your system will produce, PV panels ideally should be installed in a location that is not shaded by trees, chimneys or nearby structures.

The best orientation for a PV system is on a south- or southwest-facing roof. Flat roofs can also work because the PV array can be mounted on frames tilting south or southwest. In addition PV array can also be mounted on the ground.

Do I have enough roof area?

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.

What size PV system do I need?

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.

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. We allow 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 two billing tiers.

How much electricity will a PV system produce?

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 1,800 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.

What is a kW?

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

What is a (kWh)?

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

How much do solar systems cost?

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 averages.

Do I need to obtain a building permit?

You probably will, but you should contact the agency responsible for issuing building permits in your specific city or county to determine your local requirements. Typically, contractors will handle this responsibility on behalf of customers..

How do I find a solar installer I can trust?

Qualified contractors are your key to getting the most productive solar energy system for your home or business. Choose a reputable installer by interviewing and obtaining bids from at least three potential installers before making your selection.

The California Energy Commission website contains a list of registered solar installers, as does California Solar Statistics.

All systems must be installed in conformance with the manufacturer’s specifications and with all applicable electrical and building code standards.

Net Energy Metering (NEM) & Interconnection

Please find more information on NEM at sce.com/nem

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