Model payback with tariffs, incentives, and battery performance. Track yearly cash flows and financial outcomes. Download a clean report for quick sharing today, anytime.
| Item | Sample value | Why it matters |
|---|---|---|
| Net upfront cost | $8,800 | Higher upfront delays payback. |
| Usable capacity | 10 kWh | Sets how much energy you shift. |
| Cycles per year | 250 | More cycles usually raise savings. |
| Efficiency | 90% | Losses reduce shifted energy. |
| Peak / off-peak | $0.32 / $0.16 | The spread drives arbitrage value. |
| Maintenance | $80/year | Recurring costs reduce net benefit. |
| Year | Net benefit | Cumulative | Interpretation |
|---|---|---|---|
| 1 | $3,600 | -$5,200 | Still recovering upfront cost. |
| 2 | $3,490 | -$1,710 | Degradation slightly lowers savings. |
| 3 | $3,385 | $1,675 | Crosses simple break-even. |
| 4 | $3,280 | $4,955 | Positive net savings build. |
| 5 | $3,180 | $8,135 | Longer life increases total return. |
Upfront cost is the starting hurdle. Net upfront cost equals system cost plus installation minus incentives. A larger rebate reduces the recovery period immediately, while higher installation costs often delay simple payback by one or more years. Maintenance is applied annually, so even modest service costs can materially reduce cumulative totals over long horizons.
Year‑one shifted energy is usable capacity multiplied by cycles per year and efficiency. The calculator then reduces shifted energy by the degradation rate each year. Because arbitrage savings are shifted energy times the peak–off‑peak spread, payback is most sensitive to the rate spread and cycling frequency. A small increase in peak price can raise annual savings more than an equivalent reduction in equipment cost.
The cash‑flow table reports yearly net benefit, cumulative benefit, and discounted cumulative benefit. Simple break‑even occurs when cumulative benefit reaches zero or higher. If cumulative stays negative through the analysis horizon, the system does not break even under the assumptions. Positive net savings over battery life indicates the battery repays its cost and continues delivering value.
Discounting converts future benefits into today’s dollars using the discount rate. The discounted break‑even year can be later than the simple break‑even year because later savings are worth less. NPV summarizes all discounted benefits minus net upfront cost; an NPV above zero suggests the project clears the chosen discount rate. The chart helps you see when discounted cumulative crosses the zero line.
Use the visualization to compare the cumulative and discounted cumulative lines. When both cross above zero early, the economics are strong. If only the simple line crosses, the project may be acceptable for risk‑tolerant buyers but weaker under conservative discounting. Add backup value or demand savings only when you can justify them with your tariff or outage history. Check assumptions yearly and update rates whenever your utility plan changes significantly.
Break-even is the first year when cumulative net benefits reach zero or above. Discounted break-even uses discounted cumulative values, reflecting the time value of money at your chosen discount rate.
Discounting reduces the present value of future savings. Even if the battery pays back in simple dollars, discounted totals may take longer to cross zero because later benefits count less today.
Use your expected dispatch frequency. Daily cycling is about 365, but many households cycle less due to weather, export rules, or comfort preferences. Overstating cycles can overstate savings.
A small rate spread reduces arbitrage savings. In that case, payback often depends more on demand-charge reductions or quantified backup value than on time-of-use shifting alone.
Yes. Shifted energy declines each year by the annual degradation rate. That lowers yearly arbitrage savings over time, which is why long horizons can show slower gains than year one.
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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.