Why You Need Home Batteries (No, It’s Not Just About Blackouts)

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Home battery storage is shifting from an exotic feature of the homes of the rich to a more mainstream option for any home with solar panels, boosted by a new 30% federal tax credit. But if you think of batteries primarily as a backup technology, you’re missing out on the most important way to justify their cost: saving money on energy every day.

The new garage user: Home batteries can be installed indoors or outdoors, but many will be installed in their garage next to their car charging connector.


Hands-on with home batteries

ZDNet’s recent roundup of the best home battery systems inspired me to visit a home battery installation in the San Francisco Bay Area where a Generac PWRcell system was mounted in the garage by Northern California installer Rob Heckendorn of Future Energy Savers. The system was powered by the existing home solar panels on the roofsomething you can’t do with Tesla Powerwall home batteries, which have to be combined with the specific solar roof technology.

The Generac system is modular, allowing the homeowner to add batteries in increments of 3 kWh to 18 kWh in a single battery cabinet. In this case, they chose three modules for a total of 12 kWh of capacity, a number that Rob Heckedorn says is as close to average as he sees and enough power to run three or four of the house’s dozen circuits for a few days. .

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Think beyond blackouts

But thinking about batteries in terms of blackout coverage creates a blind spot: Yes, the US may have more power outages than other developed countries, but they remain rare. A better priority is to specify your battery system for “rate arbitrage” to save money and be greener every day.

The idea is simple: store excess free energy from your roof into your batteries instead of selling it back to a utility company that doesn’t like the idea and offers a pittance. Instead, use that stored energy later in the day during peak times to avoid the highest electricity rates while doing your part to offload the grid. It’s the missing piece that makes residential rooftop solar a more comprehensive proposition.

Some of that elegance will depend on having a solar system large enough to charge your batteries with a healthy clip, living in a home with plenty of sun, and being a customer of a utility that forces your hand with controversial duration of use of electricity rates.

How much is it?

Saving money on energy every day is important because battery storage in the home is not cheap. As a rule of thumb, you can expect a typical home battery installation to cost about the same as a full solar installation, perhaps $20,000 to $25,000. Calculating payback through daily savings is complicated, so your home battery decision should be based on your raw daily savings, believe in the more optimistic math of the salesperson, and whatever value you place on some power in a black. -out. It may not be as simple a calculation as rooftop solar payback, but to help your decision should be a new 30% federal tax credit passed as part of the recent Inflation Reduction Act.

Generac PWRcell case

This PWRcell cabinet can hold up to six battery modules with a total capacity of 18 kWh. A second cabinet can be added for a house of up to 36 kWh.


Generac, best known for generators, has recently started combining them with its home battery systems to better power homes in some situations. If your sole focus is on power during extended grid outages, an on-site generator may still be your most basic option, at least until regulators ban all combustion-powered generators.

Generac batteries and generator

Generac recently started offering technology that allows its home batteries and home generators to seamlessly transfer to each other. Buying a generator is still a good idea, especially if you want to become a grandfather before regulations can ban them.


Charging your electric car

Focused on charging your EV? Temper that: Most home battery systems hold much less than an EV battery, so you can get a small charge for your car if you want to leave something in the batteries to keep part of your house running. This is another case where looking for an installed home generator, with or without home batteries, makes the most sense.

Focus on the warranty

As with any expensive new energy technology, pay attention to warranty coverage. Most home battery brands have a 10-year warranty, but just like cars, there’s a consumable component that can change that duration. As you can see, that usage component varies by manufacturer, so an apples-to-apples comparison is impossible:

  • Generac: 10 years, 7.56 megawatt-hours throughput
  • Tesla: 10 years, 70% battery life
  • Enphase: 10 years, 7,300 fully discharged cycles, 80% retention

If you’ve installed solar for your home, you’re probably familiar with the concepts you need to know to buy home batteries, but the factors are more nuanced and the value you place on peace of mind in the event of a power outage is elusive.

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