LOS ANGELES — With fires raging throughout California, thousands of people have experienced power outages. That’s a trend that’s likely to continue, as the state’s power grid managers warn of rolling blackouts resulting from record-breaking heat this week and as climate change increases year-round fire risk. 

The usual go-to for backup power is a gas- or diesel-powered generator, but there's another, more environmentally friendly option: battery energy storage. That's the system that lets homeowners store electricity from the power grid, or from rooftop solar panels, so it can be used during a power outage. 

What You Need to Know

  • Battery energy storage systems let homeowners store electricity from the power grid or from rooftop solar panels so it can be used during a power outage

  • A variety of companies make battery energy storage systems, including Tesla, LG, Panasonic, and Sonnen

  • The California Public Utilities Commission offers a Self-Generation Incentive Program to help offset the cost

  • For California homeowners who live in high-fire-risk areas, the CPUC SGIP can reduce the cost to almost zero

How Battery Energy Storage Can Help During a Blackout

Battery energy storage systems work by storing electricity in a battery at the home — oftentimes in the garage or on the side of the house. While they often work in conjunction with solar panels to store electricity generated during the day for use at night, they can also connect to homes that receive their power directly from a utility. 

How it Works When the Power Goes Out

Using the Tesla Powerwall as an example, it will detect the outage, disconnect from the grid, and automatically restore power within a split second, so homeowners won't even know the power has gone out. 

How Long Will the Power Last?

It depends on the size of the system. The larger the battery, the more storage it provides, the more electricity can be stored. The average U.S. home uses about 29 kilowatt-hours of electricity per day, according to the U.S. Energy Information Administration.

One Tesla Powerwall is capable of storing about 13.5 kilowatt-hours of electricity, or about half of an average American home’s daily electricity usage; a similar system from LG Chem can store 12.4 kilowatt-hours. For more storage capability, battery energy storage systems can be scaled up or down, depending on a household’s electricity usage and needs for backup power.

Which Companies Offer Battery Energy Storage? 

Tesla began offering its Powerwall system in 2015, but the past couple years have seen several other players come into the market, including LG Chem (the battery subsidiary of the Korean electronics company LG), the Japanese electronics company Panasonic, and lesser-known entities such as Sonnen, Generac, and Enphase. Systems can be purchased directly from the manufacturers or through a solar installer since many battery energy storage systems are purchased in combination with rooftop solar panels.

How Much Does Battery Energy Storage Cost?

It depends on the size of the system. The more energy a person wants to store, the larger the battery that’s needed, the higher the cost. A 10-kilowatt-hour system costs about $7,000, but that does not include hardware or installation, which can push the cost upwards of $10,000.

Homeowners can, however, bring down the costs of battery energy storage systems with various incentives. In the Golden State, residents are eligible for the California Public Utilities Commission Self-Generation Incentive Program, which offers rebates for energy storage installations that can function during a power outage. 

Residential customers of Pacific Gas and Electric Company, Southern California Edison, Southern California Gas Company, or San Diego Gas & Electric are eligible for a rebate of about $250 per kilowatt-hour; that rebate covers roughly 25 percent of the cost of an average energy storage system.

Due to wildfire, the CPUC has authorized more than $1 billion in funding for the program through 2024. Communities in high-fire threat areas and that have experienced two or more utility public safety power shut-off events, as well as low income and medically vulnerable customers, are eligible for rebates of $850 to $1,000 per kilowatt-hour, making the systems “almost, if not completely, free of cost,” according to the CPUC.

Homeowners who install solar panels, in addition to a battery energy storage system, are also eligible for the federal Solar Investment Tax credit. Individuals who install such a system before the end of 2020, are eligible for a 26 percent federal tax credit on the total cost of installation.