What NPV tells you that other metrics do not
Net Present Value measures the absolute value an investment creates or destroys, expressed in today's currency. A positive NPV of $250,000 means the investment generates $250,000 of value above and beyond the minimum return required by your cost of capital. A negative NPV means the investment destroys value — you would be better off deploying that capital elsewhere at your required rate of return.
NPV's key advantage over IRR is that it accounts for investment scale. A $10,000 investment with a 50% IRR has a smaller NPV than a $10 million investment with a 20% IRR. NPV is the theoretically correct metric for maximising firm value, which is why it is the primary criterion in corporate capital allocation. IRR is widely used in parallel because it expresses return as a percentage, which is easier to compare against benchmarks and communicate to stakeholders.
Terminal value matters enormously for long-duration investments like real estate, SaaS businesses, and infrastructure. When an asset continues generating cash flows beyond the projection period, ignoring terminal value dramatically understates NPV. The Gordon Growth Model calculates the present value of all future cash flows beyond Year N as: Terminal Value = Final Year CF × (1 + g) / (r − g), where g is the long-run growth rate and r is the discount rate.
The formulas
NPV = −C₀ + CF₁/(1+r) + CF₂/(1+r)² + ... + CFₙ/(1+r)ⁿ
Discount factor (year n) = 1 / (1 + r)^n
Present value (year n) = Cash flow_n × Discount factor_n
Terminal value (Gordon Growth) = CF_n × (1 + g) / (r − g)
Terminal value PV = Terminal value / (1 + r)^n
Profitability index = PV of future CFs / Initial investment
NPV = PV of future CFs + PV of terminal value − Initial investment
Decision rule: NPV > 0 → invest; NPV < 0 → reject; NPV = 0 → earns exactly the discount rate
NPV is additive: the NPV of a portfolio equals the sum of the NPVs of its components. This allows you to rank and prioritise independent projects. When projects are mutually exclusive (either/or), choose the project with the highest positive NPV, not the highest IRR. When capital is rationed, rank by profitability index (NPV / initial investment) to maximise value per dollar deployed.
NPV decision rules and common mistakes
| Situation | Correct approach | Common mistake |
|---|
| Single independent project | Accept if NPV > 0 | Requiring IRR > hurdle instead — same answer, but NPV is more reliable |
| Mutually exclusive projects | Choose highest positive NPV | Choosing highest IRR — wrong when projects have different scales or durations |
| Capital rationing | Rank by profitability index (NPV / cost) | Choosing by NPV alone — ignores that smaller projects free capital for other uses |
| Long-duration assets | Include terminal value at an appropriate growth rate | Truncating cash flows at year 10 and ignoring continuing value |
| Risky / uncertain projects | Raise discount rate or run scenario analysis | Using the same discount rate regardless of project risk |
Frequently Asked Questions
What does a positive or negative NPV mean?+
A positive NPV means the investment generates more value than the minimum required by your cost of capital, expressed in today's dollars. A $200,000 NPV at a 10% discount rate means that after rewarding all capital providers at 10% per year, the investment creates an additional $200,000 of wealth. A negative NPV means the investment fails to earn the minimum required return — it destroys value relative to deploying the capital elsewhere at the hurdle rate. A zero NPV means the investment earns exactly the discount rate, neither creating nor destroying value. In theory, firms should accept all positive-NPV projects because doing so maximises shareholder value. In practice, capital constraints and execution risk mean firms apply additional hurdle criteria.
What discount rate should I use?+
The discount rate for NPV should reflect the opportunity cost of capital — what you could earn on a comparable-risk alternative investment. For corporate capital projects, this is typically the weighted average cost of capital (WACC), which blends the after-tax cost of debt and the required return on equity weighted by capital structure. For a business with 40% debt at 5% after-tax and 60% equity at 12% required return, WACC is 9.2%. For riskier projects, many firms add a risk premium of 2 to 5 percentage points above WACC. For personal investments, use your realistic after-tax investment alternative rate. Using a higher discount rate makes the NPV lower and the investment harder to justify — which is why discount rate selection is one of the most important and often contested inputs in financial modelling.
What is the profitability index and when should I use it?+
The profitability index (PI) is NPV divided by initial investment, plus one, or equivalently the present value of future cash flows divided by initial investment. A PI of 1.25 means you receive $1.25 of discounted value for every dollar invested. PI is particularly useful when you have capital rationing and must choose between multiple positive-NPV projects that compete for limited funds. Ranking by PI rather than NPV selects the combination of projects that creates the most value per dollar deployed. For example, two projects of $100,000 each might have NPVs of $40,000 and $30,000 respectively, but if a $50,000 project has an NPV of $25,000 (PI 1.5 vs 1.4 and 1.3), capital rationing analysis shows different optimal combinations depending on available budget.
What is terminal value and how does it affect NPV?+
Terminal value represents the present value of all cash flows beyond the explicit projection period. For most operating businesses, real estate, and infrastructure assets, value extends well beyond a 5 to 10 year model horizon. The Gordon Growth Model calculates terminal value as the final year's cash flow multiplied by (1 plus the long-run growth rate), divided by (discount rate minus growth rate). This produces a perpetuity value that is then discounted back to today. Terminal value often represents 40 to 70% of total NPV for growing businesses, which is why the assumed long-run growth rate and discount rate have outsized importance. A 1 percentage point change in the terminal growth rate assumption can change total NPV by 20 to 40% for a long-duration investment.
When should I use NPV instead of IRR?+
Use NPV as the primary decision criterion when comparing mutually exclusive projects of different sizes, when capital is not strictly rationed, and when you want to understand the absolute value created. Use IRR as a secondary metric to express return as a percentage for benchmarking against cost of capital or investor expectations. The cases where IRR fails but NPV succeeds are: comparing two projects where the smaller project has a higher IRR but lower NPV (NPV correctly identifies the more valuable project); when cash flows change sign more than once (multiple IRRs make the IRR ambiguous); and when evaluating project timing, where an IRR-only analysis may prefer a short-duration project even if a longer-duration project creates more total value. In practice, sophisticated capital allocation processes use NPV, IRR, PI, and payback period together rather than any single metric.
How does inflation affect NPV?+
Inflation affects NPV through the discount rate and through the cash flow projections. The most important rule is consistency: either use nominal cash flows (including projected price increases) with a nominal discount rate (which includes expected inflation), or use real cash flows (stripped of inflation) with a real discount rate (nominal rate minus inflation). Mixing the two gives the wrong answer. Most financial models use nominal figures because costs and revenues are naturally observed in nominal terms. The Fisher equation relates the two: (1 + nominal rate) = (1 + real rate) × (1 + inflation rate). For a 10% nominal discount rate with 3% inflation, the real rate is approximately 6.8%. When inflation is high and variable, sensitivity analysis across discount rates becomes especially important because small inflation forecast errors translate into significant NPV uncertainty.