Home battery calculator
A battery does not make electricity. It moves a kWh you would have exported cheaply into one you use at the retail rate. Whether that is worth $15,000 depends on a single number: what your utility pays for exports.
The formula this rests on
value per shifted kWh = retail rate × (1 − export credit ratio)
Under full retail net metering the export credit ratio is 1.0, so that expression is exactly zero. No battery, at any price, can save money on a flat tariff in that situation — the grid is already a free, lossless battery.
Each kWh the battery shifts is worth $0.249. It can shift about 3,645 kWh in year one, giving a 15-year net present value of -$5,003, and it never pays back.
How this is calculated, and what it leaves out
Value per shifted kWh = retail rate × (1 − export credit ratio), plus any time-of-use spread. In California: NEM 3.0 compensates exports at avoided-cost rates far below retail.
- No federal tax credit is applied. §25D covered standalone storage of 3 kWh or more, and expired for systems placed in service after 2025-12-31.
- Backup value during outages is excluded — it depends on how often your power fails and what an outage costs you.
- Throughput is capped by both the battery's cycling limit and how much surplus solar you actually have.
Where batteries do pay
- Low export compensation. California's NEM 3.0 credits exports at avoided-cost rates well below retail. Every kWh you store instead of exporting captures most of the retail rate.
- A wide time-of-use spread. Charging off-peak and discharging on-peak earns the difference, even without solar.
- Demand charges, where a residential tariff has them. We do not model these — if yours does, treat our figure as conservative.
Where they do not
- Full retail net metering on a flat tariff. No spread exists to arbitrage.
- Little or no solar surplus. An empty battery earns nothing, however large it is.
- Cheap electricity. A small spread on a low rate takes a very long time to repay $15,000.
What changed in 2026
Storage lost its federal credit alongside solar. §25D had covered standalone batteries of 3 kWh or more since 2023; it expired for systems placed in service after December 31, 2025. A 2026 cash or loan purchase gets nothing. Storage under a lease or PPA can still reach §48E, because the provider owns the hardware.
What we exclude, and why
Backup power. For some households an outage means a freezer full of spoiled food; for others it means medical equipment losing power. We cannot price that for you, and inventing a number would let the resilience case quietly rescue a bad economic one. The calculator tells you what the battery costs you in running-cost terms. Whether resilience is worth that is your call, made with the price in front of you.
Common questions
Is a home battery worth it in 2026?
It depends almost entirely on how your utility credits exported power. Where exports earn a fraction of retail — California under NEM 3.0 is the clearest case — a battery captures a real spread. Where you get full retail net metering, the grid already stores your surplus at full value for free, and a battery cannot beat that on economics alone.
Does a battery still get the 30% federal tax credit?
Not for a homeowner purchase. §25D covered standalone storage of 3 kWh or more, and it expired for systems placed in service after December 31, 2025. Storage installed under a lease or PPA can still reach the commercial §48E credit, since the provider owns the equipment.
What about backup power during outages?
That can be worth a lot, and we deliberately do not put a number on it — it depends on how often your power fails and what an outage costs you. Buying a battery for resilience is a legitimate decision. Just make it with the running-cost figure in front of you, so you know what the insurance costs.
How much can one battery actually shift?
Two limits bind at once: how much the battery can cycle, and how much surplus solar you have to store. A 13.5 kWh battery cycling daily at 90% round-trip efficiency moves roughly 3,600 kWh a year — but only if your panels are exporting at least that much.
Related: the solar buy vs. lease comparison, and our assumptions.