Batteries and backup power
A battery changes three things on a solar home: what the house can run when the grid is down, how much of the daytime surplus the household keeps instead of exporting, and how big the quote gets. Those three jobs pull in different directions, and installers often sell all three at once. This hub separates them so you can price the one you actually need.
Start with the outage question, because it is the most common misunderstanding. Ordinary grid-tied panels shut off when the utility line goes dead; that is a safety requirement, not a defect, and the outage guide explains the standards behind it and the three ways a solar owner can still keep power on. Then read the battery decision guide, which tests whether storage pays where you live, given your export rule and your rate plan. Rates themselves are EnergyBS territory, so this section links there for rate context instead of repeating it.
Two cautions apply to every page here. The federal residential clean energy credit, which used to cover batteries, ended for property placed in service after December 31, 2025, so no battery math on this site assumes it. And no page here names a battery brand or installer as a pick: the pages show how to read a specification and a price, not which product to buy.
Every guide in this section
Do you need a battery? The three jobs storage actually does
A 13.5 kWh battery added $13,120 to the modelled 8 kW system in the 2025 benchmark. When storage earns its place, and when it is an expensive accessory.
What a home battery costs installed in 2026, and what moves the price
Two primary yardsticks for a home battery's installed price: the NLR bottom-up model at $885 per kWh and Berkeley Lab's 2025 sales data, with the line items, the fixed costs that make small batteries expensive per kWh, and the cost of each kWh a battery actually delivers.
Does solar work in a power outage? Why grid-tied panels shut off, and the three ways around it
Ordinary grid-tied panels shut down when the utility line goes dead, even at noon. Why that happens, and how a battery, a backup-capable inverter or a generator changes it.
Home battery incentives after the federal credit: what each program pays and whether it is open
Federal battery credit gone, so what pays? A dated read of California SGIP, Illinois, Connecticut, New York, Maryland and Oregon programs, with status as of October 2026.
Can you add a battery to an existing solar system? AC or DC coupling, permits and tariff risk
Most existing systems can take a battery. Your inverter decides whether it is a simple AC-coupled add-on or a bigger rebuild, and the utility will want its own paperwork either way.
What do US utility battery programs pay, and are they worth joining?
What Massachusetts, Arizona, Vermont, Hawaii, Colorado and California pay for home battery dispatch, read from each program's own terms, with the fees and exit costs.
Can a home battery go in the garage? The US code rules on rooms, kWh limits and bollards
The US model residential code lists a garage first among the places a home battery may go, with an 80 kWh cap, alarms and impact protection. This guide tables every location rule, works the kWh and bollard arithmetic, and shows which states enforce it.
How much does off-grid solar cost? Battery days, December sun and the DOE 2025 price line
What an off-grid solar system costs at the DOE Q1 2025 benchmark line, sized from daily kWh, days of battery storage and December output in two saved PVWatts runs, with a year-long Denver simulation of generator days for seven designs.
Home battery warranty throughput: how many years before the MWh cap ends coverage?
The throughput caps, end-of-term capacity floors and start-date rules in four US home battery warranty documents, converted into years of coverage at half, one and one-and-a-half cycles a day, with the utility program and exclusion terms that shorten them.
How to choose between these battery guides
Pick the guide by the job you want the battery to do, because the three jobs have different prices and different evidence. If the worry is a dark house during an outage, start with the outage guide: it explains why grid-tied panels stop producing when the line goes dead and what each backup route costs the solar owner. If the question is whether storage pays at all, read the battery decision guide, which tests your export rule and rate plan. If the panels are already on the roof, the retrofit guide covers coupling, permits and the tariff risk of changing a grandfathered system.
Two public numbers frame all three. The U.S. Department of Energy's Q1 2025 residential benchmark puts an 8 kW rooftop system at $2.95 per watt DC without storage and $4.59 per watt with a 13.5 kWh battery, in 2024 dollars. On 8,000 watts that is roughly $23,600 against $36,720, so the battery line accounts for about $13,120 of a combined quote (our arithmetic on the DOE figures, checked October 30, 2026, at energy.gov/cmei/systems/solar-photovoltaic-system-cost-benchmarks). Any storage line in a quote should be judged against that gap, not against the headline price.
The federal residential clean energy credit once covered batteries of at least 3 kWh. The IRS states that it is not available for property placed in service after December 31, 2025 (irs.gov/credits-deductions/residential-clean-energy-credit, page reviewed July 4, 2026, checked October 22, 2026), so none of the battery math here assumes it. Outage frequency also varies by place: the U.S. Energy Information Administration reported that customers averaged about 5.5 hours of interruptions in 2022 when major events are included, and roughly 2 hours a year without them (eia.gov Today in Energy, January 25, 2024). A battery sized for a rare long outage and a battery sized for daily rate shifting are different purchases.
| Your situation | Question to settle first | Start with |
|---|---|---|
| Panels not installed yet, outages are the worry | Which backup routes exist besides a battery, and what do they cost | Does solar work in a power outage |
| Comparing a solar-only quote with a solar-plus-battery quote | Does storage pay under my export and rate rules | Battery or not |
| Panels already installed, battery added later | Which coupling, which permit, and does it touch my tariff | Add a battery to existing solar |
| Your utility pays low export rates | How much of the surplus can the household keep instead | Export compensation hub |