NPV (Net Present Value)

Formula

NPV = Σ_t (CF_t / (1+r)^t) − CF_0

Where:

• CF_t = cash flow at time t
• r = discount rate (WACC)
• CF_0 = initial investment (positive number, subtracted)

Key Takeaways

• NPV = present value of future cash flows minus initial investment.
• Positive NPV = project creates value.
• Discount rate = cost of capital.
• Complements IRR for investment decisions.
• Use Excel NPV() or XNPV() function.

Why NPV Matters for Solar Project Decisions

NPV converts a stream of future cash flows into a single number expressed in today’s money, which is what makes it useful for comparing projects of different sizes and durations. Two solar projects can post identical payback periods yet have very different NPVs once the actual timing and size of their cash flows are discounted at the investor’s cost of capital. A project front-loaded with strong early-year generation (and correspondingly less exposure to long-term degradation) will generally show a higher NPV than one whose returns depend on cash flows arriving many years out, even if the undiscounted totals look similar. This is also why the discount rate assumption matters so much: raise it and distant cash flows shrink faster, which can flip a marginal project from positive to negative NPV.

Worked Example

Say a project requires an initial investment (CF_0) of ₹10 crore and is expected to generate discounted cash flows over its life that sum to ₹12 crore once each year’s cash flow is divided by (1+r)^t at the chosen discount rate. NPV = ₹12 crore − ₹10 crore = ₹2 crore. Because the result is positive, the project is expected to earn more than the discount rate used, i.e., it creates value over and above the investor’s cost of capital. If the discount rate were raised (say, because the investor demanded a higher return for perceived risk), the same future cash flows would discount to a smaller present value, and the NPV could turn negative even though nothing about the physical project changed — only the assumed cost of capital did.

Related Reading

NPV is only as reliable as the cash-flow forecast feeding it, and for grid-connected solar in India that forecast is shaped heavily by the applicable net metering and billing rules — see the DISCOM net metering process guide for how state-level metering structures affect the revenue side of the model. In competitive bidding, the same discounting logic underpins tariff decisions, as explained in SECI tariff math and its effect on bid pricing. For teams that need to run these calculations directly rather than building spreadsheets from scratch, SurgePV’s solar generation financial modeling tool and QuickEstimate’s write-up on financial modeling software for solar estimation both cover how NPV and IRR are generated from yield and cost inputs.