Frequently Asked Questions

About solar power

How does solar photovoltaic energy work?

Visit our Solar Overview page to learn more.

How much maintenance is required?

Most solar installations will require little maintenance during the life of the system, and some proactive care may help you maximize the value of your investment. For example, if you live in a dusty environment, periodic washing of the panels may help increase electricity production, and inverters may need replacing, which normally occurs after the 10+ year warranty term.

How long do solar systems last?

The lifespan of a solar installation depends on the local environment and the durability of the system you purchase. A high quality solar installation can last more than 30 years.

What if there is a cloudy day?

Solar systems produce less electricity on cloudy days. The great majority of homes with solar still connect to the electric grid, drawing power from the grid when needed.

What if I'm not using electricity when the system is producing power?

In many U.S. states there is a policy called "Net Metering" which means the utility credits a homeowner for solar energy that is not consumed by the home. Those net metering credits are used up when the home takes power from the utility. Find out more at this overview of Net Metering policies.

What if net metering is not allowed in my area?

It is still possible to install solar power, but any solar power not consumed by the household at the time it is produced will be exported to the electric grid, and is often compensated at rates lower than the retail electricity rate. The actual amount of solar electricity exported to the grid will depend on a variety of factors, including the total amount of electricity consumed, the size of the solar installation, and the degree to which electricity consumption occurs at the same time as solar production.

While actual values for a house will depend on the specific electricity usage patterns in that house, Project Sunroof estimates values for the percent of electricity exported to the grid using data from NREL. The estimates are based on the relationship between the total solar electricity production and the total amount of electricity consumed by the household. The larger the solar installation is relative to the household electricity consumption, the higher the estimate of percentage of solar electricity exported to the grid.

What are the risks to getting solar power?

Before deciding to go solar, make sure to select a provider with a good track record and an understanding of how to install and maintain solar systems. When properly installed and maintained, solar panels should not pose any danger to your home. Issues related to the installation and operation of a solar system are relatively uncommon, but can include PV systems catching fire, roof leaks, and hail and/or wind damage. For more information, talk with your provider.

Will my projected solar savings match actual savings throughout the life of system?

Actual savings can vary from projected savings for a variety of reasons. Fast-growing trees can shade solar installations, reducing production over time. Utilities can change how much they charge their customers for electricity, changing the savings from solar. Policies that are beneficial to solar installations may change (e.g., Net Metering). For states without net metering, savings may also vary by the amount of solar electricity consumed in the household compared to the amount exported to the grid.

Solar power and your home

What’s the process for going solar?

Check out our guide for going solar.

What makes a roof good for solar?

The best solar roofs have large areas with South or Southwest exposure, little shade, and a roof in good condition.

What if my roof is really old?

If your roof needs to be replaced, it may make sense to replace the roof and install solar at the same time. Some providers offer a service to remove and replace a solar installation if you get a new roof in the future.

What if I have to move after a few years?

This varies by solar company, but typically you'll have the option to transfer a financed system to the new homeowner (with their consent), or buy out the rest of the contract and leave the system with the new homeowner or even bring it with you for installation in your next home. If you purchase the solar system, it's yours to handle how you would like.

Why are some parts of the roof sunnier than others?

Roof orientation matters. In the U.S., north-facing roof faces get less sun than south-facing roofs. Shading also plays a big role, whether from trees, chimneys, or nearby buildings.

What if I want to buy a high power consumption device in the future, such as a swimming pool or electric vehicle? Can I oversize my system relative to my current electricity consumption?

Sometimes you can. Different utilities have different rules on this question. Some utilities may limit the installation size to a proportion (e.g., 120%) of the electricity consumed over the prior year.

What if I own a multifamily home?

Depending on your homeowner's association, you may still be able to get solar for your home. Project Sunroof does not always know which portion of the roof belongs to which address or homeowner, so check with a solar provider to learn what’s possible in your situation.

What if I rent an apartment or rent my home?

Most solar solutions are geared toward homeowners, but there are some options for renters. For example, some utilities offer green energy options, and in some states community solar programs allow people to buy solar power from remote solar installations.

What if it snows on solar panels?

In climates warm enough to melt the snow, you can just wait until the snow melts. If you need to clear the panels, there are tools that can help. Check with your provider for recommended options.

Project Sunroof technology

What data sources does Project Sunroof use?
Why does this tool give a different estimate of solar energy production than the solar company who gave me a proposal? Or the PVWatts tool from the National Renewable Energy Laboratory (NREL)?

Solar energy production estimates depend on many factors, such as shading, typical weather in your area and equipment used. NREL, your solar provider, Project Sunroof and others may have different estimates, leading to different outputs. Additionally, Project Sunroof mapping data may be from a different period in time than other estimates, and thus may not show recent growth or removal of trees.

Many solar providers will give you a final solar production estimate based on shade readings they take while inspecting your roof.

For solar providers

I'm a solar provider and interested in reaching potential solar customers. How can I be a part of Project Sunroof?

For general inquiries, please contact us at projectsunroof-partners@google.com .