Solar Backup Batteries Explained – Are Solar Backup Batteries Worth It?

A solar battery stores electricity so you can use it later. With home solar, that usually means soaking up extra solar power at midday and using it in the evening, or keeping part of the house running when the grid goes down.

Batteries are expensive, though, and whether one makes sense depends mostly on how your utility credits solar and how often your power goes out.

How a home battery works with solar

During the day, your panels power the house first. Extra solar goes into the battery until it’s full, and only then out to the grid. After sunset, the battery covers your home’s use before you start buying power from the utility.

There are two common ways to connect a battery:

• AC-coupled: the battery has its own inverter and sits alongside your existing solar inverter. This is the usual way to add storage to a system you already own. Enphase IQ Batteries work this way.
• DC-coupled: panels and battery share one hybrid inverter. Tesla’s Powerwall 3 has a solar inverter built in, so new panels can wire straight into it.

For backup, the battery also needs a gateway or transfer switch that disconnects your home from the grid during an outage. Grid-tied equipment isn’t allowed to send power onto utility lines while crews are working on them. Our FAQ on whether solar panels work during a power outage explains why.

Whole-home vs partial backup

With partial backup, an electrician moves your most important circuits (fridge, lights, internet, a few outlets, maybe a well pump) to a separate critical-loads panel. Only that panel runs during an outage, so one battery lasts much longer.

Whole-home backup keeps every circuit available. It usually takes more battery capacity and more power output, especially for central air, electric ranges or well pumps with big startup surges. EnergySage gives a rough figure of about $34,000 for whole-home backup.

Either way, you’ll probably still ration in a long outage. The average US home uses about 865 kWh a month, or roughly 28 kWh a day (EIA), so a single 13.5 kWh battery holds about half a day of typical use. Solar panels can recharge it during the day, but cloudy stretches cut into that. Most systems let you set a reserve so part of the battery is always held for outages.

What home batteries cost

EnergySage’s July 2026 marketplace data puts a typical 13.5 kWh home battery at about $15,650 installed, before incentives. Price per kWh varies a lot by brand, installer and state.

Extra costs can include a critical-loads subpanel, a main panel upgrade, or a gateway or backup switch. A good quote lists these separately. Adding a battery at the same time as new solar can save some duplicated electrical work.

The 30% federal Residential Clean Energy Credit used to cover home batteries, but it ended for systems installed after December 31, 2025. If you lease a battery, the company that owns it may still claim a business tax credit, so ask how that shows up in your price. Some states and utilities run their own battery programs, which we cover in our guide to solar rebates and incentives.

Major home batteries and warranties

Battery	Capacity per unit	Warranty
Tesla Powerwall 3	13.5 kWh	10 years, 70% capacity retained
Enphase IQ Battery 5P	5 kWh (stackable)	15 years or 6,000 cycles, 60% retained
FranklinWH aPower 2	15 kWh	15 years or 60 MWh of throughput

Enphase also sells a 10 kWh IQ Battery 10C, and sonnen’s sonnenCore+ carries a 10-year or 10,000-cycle warranty with 70% retention. These current models use lithium iron phosphate (LFP) cells, which hold up well over thousands of cycles and are more heat-stable than the nickel-based cells used in some older home batteries. Our Tesla Powerwall guide goes deeper on Tesla’s lineup, and how long solar batteries last covers warranties in detail.

When a battery tends to pay off

• Your utility pays little for exported solar. Under California’s Net Billing Tariff, which applies to applications since April 15, 2023, exports are credited at rates usually well below retail, roughly 75% lower than under the old rules. Storing midday solar for evening use is worth more than exporting it, and the CPUC notes that adding storage is how customers get the most out of net billing.
• You’re on a time-of-use rate with a big gap between peak and off-peak prices. The battery covers your usage during expensive evening hours.
• A utility or state program pays you to share the battery. In these virtual power plant programs, the utility draws on enrolled batteries during peak demand. Massachusetts’ ConnectedSolutions pays $275 per kW each summer, which averages about $1,200 a year. Connecticut’s Energy Storage Solutions offers upfront and performance incentives, and Vermont’s Green Mountain Power has its own battery programs.
• You lose power often, or you rely on medical equipment, a home office or a well pump. In that case you’re paying mainly for resilience, and any bill savings are a bonus.

When it usually doesn’t

With full retail net metering, the grid already works like a free battery. Each kWh you export earns a credit worth about the same as a kWh you buy, so storing it yourself doesn’t save much more. A battery there mostly buys backup power.

A battery is also hard to justify on savings alone if outages are rare and short where you live. A portable generator or a small portable power station can cover a fridge and phones for far less, as long as you’re fine with manual setup and, for generators, fuel and noise.

Sources

• EnergySage: How much do solar batteries cost?
• CPUC: Net Energy Metering and Net Billing
• IRS: FAQs for modification of sections 25C, 25D and others under the One Big Beautiful Bill
• Tesla: Powerwall Limited Warranty (USA)
• Enphase: IQ Battery 5P
• FranklinWH: aPower 2 home battery
• EIA: Average US household electricity use and bills