The Time Value of Money (TVM) is the core logical foundation of modern appraisal, stating that a dollar received today is worth more than a dollar received in the future due to its potential earning capacity.
Compounding is the process of determining the future value of an investment by applying an interest rate over multiple periods, where interest is earned on previously accumulated interest.
Discounting is the inverse of compounding; it calculates the Present Value (PV) of a future sum by stripping away the expected interest that would have been earned over that period.
The mathematical relationship is expressed as: where is the future value, is the discount rate, and is the number of time periods.
| Feature | Net Present Value (NPV) | Internal Rate of Return (IRR) |
|---|---|---|
| Decision Rule | Accept if | Accept if |
| Reinvestment Assumption | Reinvested at the Cost of Capital | Reinvested at the project's IRR |
| Measure | Absolute (dollars/currency) | Relative (percentage) |
| Project Scale | Accounts for the size of the project | Ignores the absolute scale of the project |
Depreciation Error: A common mistake is treating depreciation as a cash outflow. While depreciation is an expense in accounting, it is not a cash movement; however, the tax shield created by depreciation is a relevant cash inflow.
Ignoring Inflation: If cash flows are estimated in 'real' terms (today's prices), they must be discounted using a 'real' discount rate. If they are 'nominal' (including inflation), use a 'nominal' rate.
IRR Limitations: IRR can produce multiple results or no result for projects with non-conventional cash flows (where the sign of the cash flow changes more than once).