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Solar FAQs


A solar electric system (also known as a photovoltaic system) uses solar panels installed on your roof to convert sunlight to electricity. This electricity is then converted to AC power which you can use to supply part of your electric use.

Solar electric systems have been in operation for many years. The first commercial application of solar electric power was in the aerospace industry. In the early 1950s, the aerospace industry was already using solar cells to extend the useful life of satellites. Currently, there are over 3,500 solar electric systems installed in the SMUD service territory.

Most new solar electric systems have a 20 year warranty. The average system degrades in output by approximately 1% per year. Example: In 20 years, a 1,000 watt system will produce at least 800 watts of electricity.

Maintenance and repairs

There is very little maintenance with a solar electric system. Washing the panels a few times a year will help keep the system operating at its best. Washing can be done with a garden hose and should be done early in the morning before the panels get hot.

Caution: Spraying cold water on hot solar panels can cause damage that cannot be repaired.

SMUD's PV Incentive Program requires contractors to give you a 10-year warranty. After the warranty expires, you will be responsible for finding a contractor to repair your system. Visit for a current listing of solar contractors.

Companies on SMUD's PV Contractor list are licensed by the California State License Board to install solar. SMUD recommends you cross check these contractors with the Better Business Bureau (BBB) and check all references.

No. Having a solar electric system does not mean you are "off the grid." While it is possible to design a system to produce all your power and enable you to go "off the grid," SMUD does not recommend that you install a system that large. A solar electric system produces only 3% of its yearly power in December. Therefore, you would need a very large system to produce enough power for your December needs. Conversely, such a large system would not be needed in June, when the system produces 13% of its yearly output. To effectively go "off the grid", a business would need massive battery banks, which can add 40% or more to the cost of a system.

At night, or on very stormy days, a conventional solar electric system goes dormant. During these dormant times, you will get power from the electricity grid. When the sun comes back out, the system resumes producing energy. If you don't use all the electricity that you are producing at that moment, the excess gets sent back to the electricity grid. You are credited this amount on your bill. This process is called "net metering."

Site and product selection

The typical home will need to have a southern-facing roof with little or no shade. East and west facing roofs also are viable, but their yearly output is decreased by 25% or more over the course of a year. A perfect slope for your roof would be 25% to 30%. While a solar electric system will produce power at a wide variety of slopes and orientations, it is important to try to maximize your output in relation to the size of the system.

Newer solar electricity systems produce about 10 watts per square foot of southern-facing exposure. See what your electricity usage is, and make rough calculations based on this.

Solar manufacturers have created mounting methods and equipment for most commonly used roofing materials.

SMUD does not recommend nor endorse any manufacturer. We offer rebates only for products listed on the State of California Energy Commission website. These products have been tested and approved by industry standard testing procedures.

While SMUD does maintain a list of contractors, we do not recommend any specific installer. SMUD recommends talking to several contractors during the process and checking all available references.

The size of your system should be based upon your electricity usage patterns, not the size of your roof. Customers with high electric bills may consider a larger system. For more information, click here.

Always try to get an idea what is going to be produced by the system. While it is impossible to predict the weather and its impact on the output of your system, there are formulas to determine expected output.

Any electrical device can be dangerous if opened or tampered with in any way. All products used in SMUD solar arrays are required to be UL listed and installed in a safe, code-compliant manner. However, most systems are located on the roof and therefore out danger from tampering.

In the SMUD service area over the past 20 years, hundreds of systems have been installed with very few leaks. Newer mounting systems are have improved resistance to leaks. Ask your contractor how your system will be mounted and how it will be sealed.

Yes, many companies have large lots or acreage to accommodate ground-based systems or parking lot covers with solar installed.

System size, product availability, and location impact the installation times dramatically. Talk to your contractor about installation times. Permitting, design and product delivery can add a month or more to the process.

Your solar electric system will be on your roof for at least 20 years, so the roof should be in a condition to last that long.


Yes, solar electricity lowers your bill, but you must still factor in the upfront cost of the system.

The most cost-effective installations are in businesses that have large electric bills. However, SMUD has found that many businesses install solar for environmental benefits.

Net metering is a billing method that gives you credit for excess electricity your solar electric system produces. SMUD rolls back your meter if you produce more energy than you use. When your house uses power from your solar electric system, you are not buying power from SMUD. That lowers your SMUD bill.

Yes, however, you should not oversize your solar electricity system to make more than you use. SMUD will only pay incentives for the system size needed to offset all or part of your 12-month historic use. State legislation that took effect in January of 2011 requires utilities like SMUD to pay for excess generation, but the amount paid may not be at retail rates. Refer to the "Net Metering for Qualifying Facilities" rate schedule for more information.

Tax incentives may vary over time. Consult with your tax consultant before making a purchase decision. They'll let you know the latest federal tax incentives and their possible benefit to you.

System prices vary by size and technology. The more expensive systems are ones that integrate with concrete tile roofs. The least expensive ones are traditional framed modules mounted on the roof. Prices in the SMUD service generally range between $8 and $11 per watt. This is before taking tax credits and rebates into account.

Payback time is determined by many factors, most importantly the amount of your current electricity bill. Customers with lower bill amounts typically have a 20-plus year payback period. Customers who have larger bills may see a return on their investment in as little as 7 to 10 years.

No. SMUD does not sell solar electric systems. SMUD's does provide rebates to customers to offset the cost of installing their own systems.

Click here for the current rebate.

If you are buying a system from a contractor on the SMUD list, the contractor will take care of the paperwork. If you are installing the system yourself, you can download the forms and the handbook at

You can install more solar on an existing system, but only the new portion will qualify for the current rebate amount.

Finding a contractor

Download SMUD's solar contractor list and talk to as many contractors as possible. The contractor you select will place a rebate reservation with SMUD. This will start the SMUD inspection procedure.

Many contractors on the SMUD list also offer SMUD financing.

SMUD provides information to help you, but offers no direct recommendations or assistance. Many prospective solar customers take SMUD's homeowners class at our Energy & Technology Center at 6501 S Street. Check here for upcoming classes.

A contractor should have a C-10 electrician's license or a C-46 solar installer license. SMUD also recommends you use a NABCEP certified installer.

Additional resources

California Energy Commission

California Solar Energy Industries Association

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