Home Solar Batteries in 2026: Backup vs Bill

Two different jobs

Backup and bill management are different designs. A battery sized for one may be wrong for the other.

Backup means selected circuits stay on when the grid is down. That requires an inverter that can form a local grid and a transfer switch or a gateway that disconnects from the utility. The circuits have to be chosen. Refrigerators, a few lights, the modem, and a furnace blower are a different load than central air conditioning.

Bill management means charging when solar, or cheap overnight power, is available and discharging when retail power is expensive or when you would otherwise export at a low credit. In California's net billing tariff this is often the economic story. In a place that still credits exports near retail, the bill-management case is weaker and the backup case may be the only one you care about.

Saying yes to a battery in the first meeting, before those jobs are separated, is how the price jumps without a purpose. Ask which job the proposal is solving.

What the 2025 installations looked like

Berkeley Lab reported that storage was attached to 37 percent of U.S. residential solar installs in 2025, up from 25 percent in 2024, and that the median residential storage capacity was 13.5 kWh.

Those figures are in the August 2026 Berkeley Lab data update. They describe the market. They are not a recommendation. 13.5 kWh is on the order of a single common home battery. It might cover a night of light loads. It will not cover several days of air conditioning.

The same update reported that, among cash-purchase residential systems, median prices were about $2.10 per watt higher for solar paired with storage than for stand-alone solar. Loan-financed differentials were smaller in that dataset. Ongoing interest is not in those up-front prices. A battery can be the right buy and still be a large share of the invoice.

Capacity in kilowatt-hours is the tank. Power in kilowatts is the faucet. A battery that holds 13 kWh but can only deliver 5 kW will not start a large air conditioner even if the tank is full. Ask for both numbers, and for the continuous power of the backed-up panel.

Outages, storms, and realistic hours

Hours of backup equal stored energy divided by the load you actually leave on, minus conversion losses.

If you leave on 1 kW of loads, 13 kWh of usable storage is on the order of half a day, not a week. Air conditioning can be several kilowatts by itself. People in hurricane and wildfire country sometimes want days of autonomy. That is a much larger battery, a generator, or a willingness to live with a very small set of circuits. None of those options is shameful. Pretending a single battery is a bunker is the problem.

Snow and ice can cover a roof, and a battery in the garage does not clear the modules. See snow and cloudy winters. We are not claiming batteries are required by any insurer.

Medical equipment is a separate conversation with your doctor and the utility's medical-baseline or outage programs, where those exist. Do not size that need off a solar brochure.

Why the estimate on this site ignores batteries

The calculator illustrates a share of the electric bill. It does not price storage or model an outage.

Adding a battery rarely increases annual solar production. It moves production from one hour to another. Our dollar range would be misleading if we added a battery 'savings' number without your tariff and your outage goal. We leave it out on purpose.

If an installer shows battery savings, ask whether those savings are avoided retail purchases, export shifting, or a backup value they converted into dollars. Backup value is mostly the outages you did not suffer. It is real to you and hard to put on a spreadsheet without inventing an outage schedule.