Home batteries versus gensets

The risk of grid blackouts in the United States is rising and the Department of Energy has said the incidence of extreme weather-related power outages rose 80% from 2011 through 2023. With the grid aging and in need in of repair, homeowners are turning to backup power at home.

Two main options exist: traditional gas generators and BESS. How do they compare?

Gas generators typically run on diesel, propane, or natural gas. Home BESS are most commonly paired with a rooftop solar array.

When it comes to upfront cost, gas generators have the advantage. Based on figures from product review website CNET, an average home battery system costs $10,000 to $20,000. Standby gas generators cost around $7,000 to $15,000. BESS costs are reduced 30% by a federal Investment Tax Credit, however, whether paired with solar or not.

Home batteries typically have lower operating and refueling costs though that varies with the price of electricity and cost of rooftop solar. Batteries can be charged by the grid or a rooftop solar array, refueling themselves. The cost to refuel gas generators is typically more expensive, though that depends on the local cost of diesel, propane, or natural gas.

The lifetime of a home battery is generally around 10 years while a generator can operate for 20 years or more, albeit with regular maintenance and repair costs.

The chart below, from solar and energy storage marketplace operator EnergySage, highlights expected costs over 20 years, for battery storage and generators, assuming a home battery includes the cost of installing solar.

From an operational standpoint, a home battery has advantages. Units are typically smaller than gensets, can be wall-mounted inside a garage or outside. Gas generators are typically quite noisy during operation.  

Gas generators also pose a health hazard as they produce carbon monoxide. If a gas generator is portable it is critical to operate it outside, as advised by federal body the Occupational Safety and Health Administration, as carbon monoxide exposure due to indoor gas generator operation can be fatal.

“If you own a portable generator, remember to place it outdoors at least 20 feet from your home’s doors, windows, or vents,” said regualtor and government agency the Texas Department of Insurance. “Keeping a distance helps protect you from carbon monoxide gas, which is colorless, odorless, and potentially deadly.”

Generators typically have an advantage in power output. While whole-home backup power with batteries is possible, some homes may require two batteries or more to back up the whole property. With a single battery, customers typically work with a solar installer to select several critical breakers in the main panel to back up with battery power.

In several states, batteries can participate in electricity grid export programs, which involve aggregating numerous such systems into a virtual power plant (VPP) which can strengthen the grid and remunerate participating homes for their contribution to supplying network electricity during periods of peak demand. Solar installer Sunrun, for example, pays its customers $400 per year to enroll in its VPP program in selected states.

The verdict: with more flexible installation location options, a quiet, sleeker design, and effortless refueling, home batteries present an easier-to-maintain backup power option. Generators have an advantage in upfront cost but, over the life of refueling and repairs, they may pose a higher lifetime cost. What’s more, generators are noisy and pose local health risks with their carbon monoxide emissions.

Now is a great time to begin the solar and battery energy storage journey. EnergySage, a free service that makes it easy to go solar, can help find trusted, reliable, local solar installers that offer competitive pricing. The company has hundreds of pre-vetted solar installers competing for business, ensuring high-quality solutions and potentially saving 20% to 30% compared with finding an installer independently. EnergySage free to use and does not make sales calls until an installer is selected and takes customer contact details. Personalized solar quotes are easy to compare online and EnergySage offers access to unbiased energy advisors to help every step of the way. Get started here.

From pv magazine USA.