Note that the IRR equation is the same as the NPV equation, except that to find the IRR the equation is solved for the particular discount rate, IRR, which forces the project’s NPV to equal zero (the IRR) rather than using the WACC in the denominator and finding NPV.
Thus, the two approaches differ in only one respect:
In the NPV method, a discount rate is specified (the project’s WACC) and the equation is solved for NPV, while in the IRR method, the NPV is specified to equal zero and the discount rate (IRR) that forces this equality is found.