4.4Investment decisions (NPV, IRR, ROI)
The essentials in 30 seconds
- Principle: investing means committing money today for future gains — knowing one euro tomorrow is worth less than one euro today (time value of money).
- Four criteria: NPV (value creation), IRR (return, vs cost of capital), payback (time risk) and ROI (order of magnitude).
- Judgment essential: these tools rationalise without replacing judgment — assumption reliability, risks, strategy.
Running mini-case — Rachid: invest or not?
With his costs, budget and dashboard in hand, Rachid considers an investment in Algiers (equipment raising his capacity). The seller promises tempting future gains. Rachid refuses to decide by feel: he compares future flows with the initial outlay by discounting them, crosses NPV, IRR, payback and ROI, then questions his assumptions before deciding. We decide with him.
Sequel of cases 4.1-4.3 — Rachid moves from day-to-day steering to a future choice.
1. Committing today for tomorrow
Investing means committing money today for future gains (machine, premises, acquisition). The common principle of selection tools: compare future cash flows with the initial outlay, knowing one euro tomorrow is worth less than one euro today (the time value of money).
Rachid applies it: a gain promised in several years is not worth the same sum today — it must be discounted before comparing.
2. NPV, IRR, payback, ROI: each one angle
The NPV (Net Present Value) discounts all future flows and subtracts the investment: positive, the project creates value. The IRR (Internal Rate of Return) is the project's return, vs the cost of capital. The payback (recovery period) measures time risk. The ROI gives an order of magnitude (gain over investment).
Each sheds light on one angle: NPV on value creation, IRR on return, payback on risk, ROI on an order of magnitude. Rachid crosses them instead of watching one alone.
3. Judgment stays essential
These tools rationalise the decision, but judgment (assumption reliability, risks, strategy) stays essential. Testing the solidity of expected future flows often changes the conclusion.
Figures inform the decision; they do not take it for you: Rachid decides by crossing priced criteria, risks and strategy.
🔎 Concrete example — The time value of money (Rachid's case)
Why Rachid discounts before comparing.
A gain promised in several years is not worth the same sum today.
NPV: discount each future flow, then subtract the investment.
Positive NPV → the project returns more than the cost of capital.Result: fairly compare flows placed in time.
Reflex: cross NPV, IRR, payback and judgment.
Section vocabulary
- NPV
- Net Present Value: sum of discounted future flows minus the initial investment; positive, the project creates value.
Simple example: Rachid's project NPV discounts each future gain before subtracting the outlay.
What it is not: a simple total of future gains with no discounting.
Reflex: positive NPV = creates value; negative = caution.
- Discounting
- Bringing a future value back to today's value, because one euro tomorrow is worth less than one euro today.
Simple example: Rachid brings each future gain back to present value before adding.
What it is not: adding euros from different years as if they were worth the same.
Reflex: as soon as you compare money over time, discount.
- IRR
- Internal Rate of Return: the project's rate of return, vs the cost of financing or capital.
Simple example: Rachid compares his equipment's IRR with his financing cost.
What it is not: a gain in euros (it is a rate, a return).
Reflex: always compare IRR with the cost of capital.
- Payback (recovery period)
- Time needed for gains to repay the initial investment; time-risk indicator.
Simple example: Rachid watches how long his outlay takes to be recovered.
What it is not: the project's total profitability (it ignores the after).
Reflex: use it to judge time risk, never alone.
- ROI
- Return On Investment: simple return ratio (gain over investment).
Simple example: Rachid uses it for a quick order of magnitude to communicate.
What it is not: a rigorous time-aware criterion (it is approximate).
Reflex: ROI to communicate, NPV and IRR for rigour.
In practice — Evaluating an investment's profitability (Rachid's case)
- Estimate the initial outlay and the project's expected future cash flows.
- Calculate NPV: discount future flows and subtract the investment; positive, the project creates value.
- Estimate IRR (return, vs financing cost) and the payback period (risk).
- Complete with ROI for an order of magnitude, then decide by crossing these criteria with risks and strategy.
Ready-to-say script — defend an investment choice (1 min)
“Here is the project: initial outlay vs discounted future flows. NPV says whether it creates value, IRR its return vs our financing cost, payback our time risk. I also tested our flow assumptions: here is what weakens them. I propose deciding by crossing these four angles, not on one figure.”
To say before deciding: crossed criteria + assumption solidity — without drowning in technique.
Copy-paste template — investment decision sheet
PROJECT: _______________
INITIAL OUTLAY: _______________
EXPECTED FUTURE FLOWS: _______________
NPV (value creation): _______________
IRR vs COST OF CAPITAL: _______________
PAYBACK (time risk): _____ / ROI (order of magnitude): _____
FRAGILE ASSUMPTIONS + RISKS: _______________
DECISION: _______________Small business / small budget
Small amount: simplified NPV + payback are often enough — the point is discounting and testing the assumption.
SME Algiers
Include real local collection delays: a late gain weighs less than a fast gain.
Strategic project
Add the non-priced (position, learning) beside criteria — without mixing it into figures.
Management beginner
Have future flows challenged by an outsider before deciding.
✓ Best practices
- Always discount future flows (time value of money).
- Cross several criteria: NPV and IRR (rigour), payback (risk), ROI (communication).
- Test the solidity of future flow assumptions (scenarios).
✗ Common pitfalls
- Adding flows from different periods without discounting.
- Relying on one criterion alone (each has limits).
- Forgetting the decision mostly depends on assumption reliability.
Key takeaways
- Choosing an investment = comparing future flows with the initial outlay, accounting for the time value of money.
- NPV: discounted future flows minus investment; positive = value creation.
- IRR: project return (vs cost of capital); payback: recovery period (risk).
- ROI: simple return ratio; these tools rationalise decisions without replacing judgment.
48h challenge — apply tomorrow
Take 1 investment project (Rachid's or yours), list outlay vs expected flows, note what each criterion (NPV, IRR, payback, ROI) would teach you and 1 fragile assumption to test.
- I can explain the time value of money.
- I can name the 4 criteria and their angle.
- I have framed (or scheduled) 1 investment decision with assumptions.
Frequently asked questions
Why “discount” future flows? Isn't one euro one euro?
No: one euro today is worth more than one euro in a year. First, today's euro can be invested and earn. Then inflation erodes purchasing power. Finally, a future gain is uncertain while a euro in hand is certain. Discounting brings future flows back to today's value: without it, you would add euros of different values, distorting everything.
NPV, IRR, payback, ROI: which one to use for deciding?
Ideally combine them: NPV judges value creation (positive = returns more than the cost of capital), IRR expresses return as a percentage, payback measures time risk (“how long to recover my money?”) and ROI gives a quick order of magnitude. In practice: NPV and IRR for rigour, payback for risk, ROI for communicating. But none replaces judgment on assumptions, risks and strategy.
Rachid hesitates over equipment: tempting future gains vs immediate outlay. He discounts flows, subtracts the investment and gets a positive NPV. What does it mean?