About the BESS IRR / NPV
IRR and NPV are the two core financial metrics for a battery energy storage (BESS) project. NPV discounts every future cash flow — revenue from arbitrage, peak-shaving, and ancillary services minus operating cost — back to today and subtracts the capex; IRR is the discount rate at which that NPV is zero. Together they tell you whether stacked BESS revenue justifies the investment.
Formula
NPV = Σ CFₜ ÷ (1 + r)ᵗ − Capex
- CFₜ
- Net cash flow in year t (revenue − opex, ₹)
- r
- Discount / hurdle rate
- t
- Year (1…N)
- Capex
- Upfront project cost (₹)
IRR = the rate r for which NPV = 0
- IRR
- Project's inherent annual return; compare to the hurdle rate
How to calculate it
- 1Model each year's revenue by stacking the streams the BESS can earn — energy arbitrage, peak-shaving/demand-charge savings, and ancillary/frequency services.
- 2Subtract annual operating cost and account for round-trip efficiency and capacity fade (augmentation).
- 3Discount every year's net cash flow to present value and subtract the capex to get NPV.
- 4Solve for the discount rate that makes NPV zero to get the IRR, then compare it against your hurdle rate.
Worked example
A standalone BESS earning only single-use arbitrage may return a single-digit IRR, but stacking arbitrage with ancillary services and demand-charge savings on the same asset can lift the IRR into the low-to-mid teens — the difference between a marginal and a fundable project.
What you can calculate
- IRR %
- NPV ₹
- Payback years
- Discount rate
Standards & references
Frequently asked questions
What is a good IRR for a BESS project?
It depends on the revenue model. A single-use battery often struggles to clear a double-digit IRR, whereas a project that stacks arbitrage, ancillary services, and demand-charge savings can reach the low-to-mid teens. Compare the IRR to your cost of capital / hurdle rate — an IRR above it means the project creates value.
Should I use NPV or IRR to decide?
Use both. IRR is a rate you can compare to your hurdle rate, but it can mislead with unusual cash-flow patterns. NPV gives the actual rupee value created at your chosen discount rate. A positive NPV at your hurdle rate is the decisive test; IRR is the intuitive headline.
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