Is a home battery worth it?
Verdict · California (US · NEM 3.0)
On hold — not yet computable
We don’t publish a payback we can’t stand behind. The US value model is ready, but it runs only on sourced, dated tariff and spec data — and California’s are still pending verification. No number is shown rather than a wrong one.
HOLD: peak import tariff (import_peak) not sourced
For the US (NEM 3.0 era) a battery’s value is three independent streams, each computed or held — never silently zeroed:
- Self-consumption. Solar that would otherwise export is stored and used at peak, valued at the avoided peak import rate minus the export it forgoes — the main earner now that export is near-worthless.
- Arbitrage. Throughput beyond your solar surplus is charged off-peak and discharged at peak, valued at the peak-minus-off-peak spread.
- VPP. A utility virtual-power-plant credit, where one exists and is sourced. Absent ⇒ $0, never guessed.
Capacity fades linearly from 100% in year 1 to 70% at the 10-year warranty end, scaling the annual value each year. Payback is the first year cumulative value clears the net install cost.
Inputs awaiting sourcing
- peak import rate
- off-peak import rate
- export rate (NEM 3.0)
- install cost
- battery usable capacity
- battery round-trip efficiency
Each must be two-sourced and dated before this page computes a California verdict (AUDITABLE_CALCULATION_STANDARD / TABULATED_DATA_DOCTRINE).
Incentives
Federal: $0. IRS §25D residential clean energy credit — 0% for battery systems placed in service on/after 2026-01-01. State incentives (e.g. CA SGIP) are applied only once sourced and dated — none are assumed here.
The result above is computed from the model before any of the links below and ignores them — placement never changes the recommendation.
Gear worth a look
Sources
- PLACEHOLDER — verify against Tesla Powerwall spec sheet + an independent measurement/source
- IRS §25D residential clean energy credit — 0% for battery systems placed in service on/after 2026-01-01