How long does a solar battery take to pay back?

Divide the installed battery cost by the annual savings from shifting solar energy to evening use and avoiding peak rates: a $10,000 battery saving $1,200 per year pays back in about 8.3 years. The calculator applies your battery size, usable capacity, tariff structure, and local rates to project the payback period and lifetime return.

What does usable capacity mean?

Usable capacity is the portion of the battery's rated kilowatt-hours you can actually cycle — most lithium batteries limit depth of discharge to 80–90% to protect lifespan. A 13.5 kWh battery with 90% usable capacity stores about 12.2 kWh per cycle. The calculator uses usable capacity, not the raw rating, for the savings math.

How much energy can I shift with a battery?

One full usable cycle moves that many kilowatt-hours from solar production time to evening peak hours. A 12 kWh usable battery can shift roughly 12 kWh per day, which at a $0.30 peak versus $0.10 solar-export gap saves about $2.40 per cycle. Daily savings compound into the annual figure the calculator reports.

Does a battery work with time-of-use tariffs?

Yes — batteries are most valuable where peak rates are much higher than off-peak: charge from solar or cheap overnight power and discharge during the peak window. The calculator models the rate gap you enter, so the payback reflects your actual tariff structure rather than a generic assumption.

What about battery degradation?

Lithium batteries typically retain 80% capacity after 3,000–5,000 cycles, or roughly 10 years of daily cycling, so the usable capacity — and the savings — slowly decline over the battery's life. The calculator models this decline, giving a more honest payback than a flat-everything assumption.

Is the payback guaranteed?

No — payback depends on your actual tariff, solar production, usage patterns, and installation cost, all of which change over time. The calculator is a planning model from your inputs; a professional solar installer should confirm sizing, and local incentives like net metering and battery rebates can shorten the real payback significantly.

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Solar Battery Payback Calculator | Estimate Storage ROI

Work out whether a home solar battery is worth it — from installed cost, usable capacity, and your tariff structure, see the payback period, lifetime return, and how much peak-rate energy you can shift each day.

Last updated: August 2026 · Free · No sign-up required

Solar battery payback calculator: estimate simple storage payback using cost, capacity, cycles, incentives, and energy value.

How this tool works

All results depend on user-entered assumptions. Use current local tariffs, system specifications, and professional estimates for decisions.

Worked example

Enter representative inputs, review the result, and adjust assumptions to compare scenarios.

Frequently asked questions

What does this calculator estimate?

It provides an assumption-based planning estimate using the inputs shown on the page.

Should I use regional defaults?

Use current local rates and provider quotes whenever possible; undated averages can mislead.

Are taxes and fixed charges included?

Only if you include them in the entered rates or costs. Utility tariffs and fees vary.

Can prices change?

Yes. Electricity, fuel, public charging, and equipment costs can change over time.

Is this a quote or engineering analysis?

No. It is an educational estimate and not a purchase quote, design, or professional advice.

What should I verify next?

Confirm assumptions, local rates, equipment specifications, incentives, and installer or utility requirements.

Quick reference

Battery Size	Usable Capacity (90% DoD)	Shifted per Day (approx.)	Est. Annual Savings*
5 kWh	4.5 kWh	4 kWh	~$260
10 kWh	9 kWh	8 kWh	~$520
13.5 kWh	12.2 kWh	10 kWh	~$650

*Assumes $0.18/kWh peak-to-off-peak spread, 100% cycling, grid-tied arbitrage only.

battery_charging Payback math

Cost vs savings over time.

percent Tariff arbitrage

Shifted kWh × rate spread.

lightbulb Pro tip

Don't forget backup value.

lightbulb Worked example

A $10,000, 13.5 kWh battery (90% usable) shifting $0.30 peak vs $0.10 export energy daily.

Result: About 11.3 years payback; faster with rebates or higher rate gaps.

Formula & methodology

Formula: Usable Capacity = Rated kWh × Depth of Discharge. Annual Savings = Shifted kWh × (Peak Rate − Off-Peak Rate). Payback Years = Installed Cost ÷ Annual Savings.

How battery payback is calculated

The tool applies usable capacity = rated kWh × depth-of-discharge, then annual saving = usable kWh × rate gap × 365, and payback = installed cost ÷ annual saving. The rate gap is the difference between your peak and off-peak or export rates — the value of shifting solar energy to evening hours.

Example: a 13.5 kWh battery at 90% usable shifting $0.30 peak vs $0.10 export energy saves 12.15 × $0.20 × 365 ≈ $887 per year — an $10,000 battery pays back in about 11.3 years.

Reading the result: payback depends entirely on your rate structure — batteries are poor value where peak and off-peak rates barely differ. Degradation slowly reduces the usable capacity over the battery's life, and local incentives can shorten the real payback significantly.

Authoritative source: https://www.energy.gov/eere/solar/homeowners-guide-going-solar

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