# ROI and payback: is an investment worth it? > Two simple tools to decide: return on investment measures the gain, payback measures how fast the investment pays for itself. - Source : https://industryhub.site/en/learn/economics/roi-payback - Track : Industrial economics - Level : Practitioner - Reading time : 7 min - Language : English ## The question everyone asks Before signing off an investment, one question always comes back: **"what does it return, and how fast?"**. Two simple indicators answer it: payback and ROI. ## Payback The **payback period** is the time after which the gains have repaid the initial investment. Its simple form fits on one line: $$\text{Payback} = \frac{\text{Investment}}{\text{Annual gain}}$$ Example: you install heat recovery for **€60,000** (CAPEX), cutting the gas bill by **€20,000 per year**. The payback is $60\,000 / 20\,000 = 3$ years. It is visualised by the **cumulative cash flow**, which starts at the negative investment and crosses zero at year 3: After that, the €20,000/yr are net gain. The **shorter** the payback, the more attractive the project: you recover your stake fast and reduce risk. In practice, industry readily accepts projects under **2 to 3 years**, hesitates between 3 and 5 years, and demands strategic justification beyond. ## ROI (return on investment) **ROI** measures not the speed but the **magnitude** of the gain, as a percentage: $$\mathrm{ROI} = \frac{\text{Total gains} - \text{Investment}}{\text{Investment}} \times 100$$ Take the heat recovery again: over 10 years it returns €200,000 of savings for €60,000 invested, i.e. $(200\,000 - 60\,000)/60\,000 \times 100 = \mathbf{233\%}$. Each euro invested returned 2.33 more. ## Payback, ROI… and discounting The two are complementary: **payback** measures the **speed** (in years), **ROI** the **magnitude** (in percent). But both ignore one reality: **a euro tomorrow is worth less than a euro today**. For large, long projects you discount the flows with the **net present value**: $$\mathrm{NPV} = \sum_{t=1}^{n} \frac{CF_t}{(1+r)^t} - I_0$$ A project creates value if its NPV is positive; the **IRR** (internal rate of return) is the rate $r$ that makes NPV zero, to be compared with the cost of capital. Simple payback remains the everyday screening tool; NPV and IRR settle the heavy trade-offs. ## The pitfalls 1. **Forgetting hidden costs**: an automation project is not just hardware; integration, training and maintenance stretch the real payback. 2. **Overstating the gains**: taking the optimistic scenario rather than the prudent one. A payback announced at 2 years that drifts to 5 destroys trust. 3. **Ignoring the lifetime**: a 4-year payback on equipment that lasts 5 years leaves little margin. ## Key takeaway Payback tells you in how many years an investment pays for itself; ROI tells you how much it returns as a percentage. Short payback and high ROI = an attractive project. For long projects, you discount the flows (NPV, IRR).