Home › Batteries and backup power
Batteries and backup power
What a home battery costs, what it will actually run, and the honest answer to whether it pays for itself.
The short answer: a battery is the only way solar keeps your lights on during a blackout. It costs roughly $1,000 per kilowatt-hour installed, so a typical unit lands somewhere around $12,000 to $16,500. Buy it for outage protection, not because the arithmetic works — in most places it doesn’t yet.
First, the thing most people don’t know
Solar panels alone do not work during a power cut. When the utility goes down, a standard grid-tied system shuts itself off — at noon, in full sun, with the panels perfectly capable of producing.
It’s a safety requirement. A system feeding power into the neighborhood wires during an outage could electrocute the crews repairing them, so every grid-tied inverter is built to detect the outage and stop.
If backup power is your reason for wanting solar, the battery isn’t an upgrade, it’s the entire point. Learn this before you sign, not after.
What it costs
Home batteries are priced by storage capacity in kilowatt-hours (kWh) — how much electricity they hold. Roughly $1,000 per kWh installed, though the spread is wide depending on brand, how many you install, and how complicated the electrical work is.
| Size | Rough installed cost | Realistically covers |
|---|---|---|
| 5 kWh | $5,000 – $8,000 | Fridge, lights, internet, phones — overnight |
| 10 kWh | $10,000 – $14,000 | The above plus a well pump or furnace fan |
| 13 kWh | $12,000 – $16,500 | Essentials comfortably for a day or so |
| 26 kWh (two units) | $24,000 – $33,000 | Most of a normal household, briefly including AC |
Note what’s missing from that table: air conditioning and electric heat, except at the largest sizes and not for long. Those are the loads that empty a battery fastest.
Batteries used to qualify for the 30% federal residential credit alongside panels. That credit expired on December 31, 2025, so a homeowner buying a battery today gets nothing back from the IRS.
Some state and utility programs still pay toward storage — Illinois, for instance, has a storage rebate — but read the conditions. Taking a utility storage rebate sometimes changes how you’re credited for exported power, which can cost more than the rebate is worth. More on what changed →
What a battery actually runs
Two numbers matter and they’re different things. Capacity (kWh) is how much it holds. Power output (kW) is how much it can deliver at once.
A battery can have plenty stored and still fail to start your air conditioner, because the compressor demands more instantaneous power than the unit can supply. Ask about both figures.
Rough overnight draw for common loads:
- Refrigerator — about 1–2 kWh
- Lights and electronics — about 1–2 kWh
- Furnace fan (gas heat) — about 2–4 kWh
- Well pump — about 1–2 kWh
- Window air conditioner — about 6–12 kWh
- Central air conditioning — 20 kWh and up
Which is why most installations back up a critical loads panel — a subpanel wired to the circuits you truly need — rather than the whole house. It’s cheaper and the battery lasts far longer.
Does it pay for itself?
Usually not on savings alone, and it depends almost entirely on your net metering rules.
| Your situation | Battery economics |
|---|---|
| Full retail net metering | Weak. The grid already stores your surplus at full value. A battery is buying outage protection, nothing more. |
| Net billing / low export rates | Much stronger. If exports earn 5¢ and power costs 25¢, storing your own is worth 20¢ a kilowatt-hour. |
| Time-of-use rates | Moderate to good. Charge cheap, use during expensive evening hours. |
| Frequent or long outages | The real case. Value isn’t measured in cents — it’s the freezer, the sump pump, the medical equipment. |
That last row deserves saying plainly. If you lose power several times a year, or if someone in the house depends on equipment that needs electricity, a battery can be entirely worth it while never paying back a cent. That’s a legitimate reason to buy one. Just be clear with yourself about which reason you’re buying for.
Practical questions before you buy
- Whole home or critical loads? Critical loads is cheaper and lasts longer. Which circuits, specifically?
- Capacity and output? Both numbers, in kWh and kW.
- Will it recharge from the panels during an outage? Some setups do, some only charge from the grid — which is useless in a multi-day cut. This is a crucial question and easy to forget.
- Warranty length and retained capacity? Ten years is common, often guaranteeing about 70% of original capacity at the end.
- Where does it go? Garage, basement or outside wall. Some have temperature limits that matter in an Illinois winter.
- Can it be added later? If you’re unsure, ask whether the system is storage-ready and what retrofitting would cost.
You don’t have to decide now
Most systems can take a battery later. If backup isn’t your main motivation, it’s reasonable to install panels now, live with the system for a year, and see whether you actually miss it.
Battery prices have fallen steadily. Waiting is not obviously the wrong move.
Sources
- EnergySage, Home battery storage costs.
- EnergySage, Battery backup vs. generators.
- Internal Revenue Service, Fact Sheet FS-2025-05 — expiry of the residential credit.
- DSIRE, State storage incentives.