Home Battery ROI Calculator
See how long a home battery takes to pay back, what it saves every year, and whether it still makes money after its warranty — with your real electricity rates and incentives.
1 Your battery & situation
US average residential ~18¢/kWh (Nov 2026); peak/off-peak are typical utility TOU values. Source: EIA, 2026-11.
The 30% federal credit for purchased systems ended Dec 31, 2025. See what still qualifies →
2 Your results
Estimates only — actual savings depend on your utility's rate structure, weather and usage. See the methodology below for every assumption.
Battery capacity fade
linear model to warranty floorCumulative savings vs. investment
breakeven = where the curve crosses the lineCompare battery sizes
price scaled linearly from your cost per kWh| Capacity | Est. installed cost | Year-1 savings | Payback | Lifetime net gain |
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How this calculator works (methodology & assumptions)
We keep the model simple and transparent so you can check the math yourself:
Solar mode: daily saving = min(solar surplus, capacity × cycles) × efficiency × rate
Degradation: capacity(y) = capacity × [1 − (1 − EOL%) × y / lifespan]
Payback = first year where cumulative savings ≥ net cost (interpolated)
- Degradation declines linearly from 100% to your warranty floor (default 70%) over the lifespan; yearly savings scale with remaining capacity.
- Round-trip efficiency (default 90%) accounts for charging/discharging losses.
- Time-of-use assumes cycling between off-peak charge and peak discharge each day; with solar, stored surplus is valued at the peak rate.
- Flat rate + no solar yields ~zero energy savings — a battery's value there is backup power, which this calculator does not monetize.
- Taxes, demand charges, export tariffs and financing costs are excluded.
Product data (updated 2026-11-06): Tesla Powerwall 3 — 13.5 kWh / $11,500 · Enphase IQ 5P — 10.1 kWh / $10,000 · LG Home 8 — 9.6 kWh / $9,500. US reference installed price — actual prices vary by market and installer (FX rates updated 2026-11-06).