1. Comparing Projects Using Time Value of Money
Net Present Worth, Equivalent Annual Worth, and IRR

2. Reviewing…NPW Two approaches to handle differing project lives:
Common Multiple Period: Projects are assumed to be repeated until a common multiple point in time is established.
Study Period: Select a study period for both projects and estimate cash flows to conform to the study period.

3. Equivalent Annual Worth Analysis
Equivalent Annual Worth (EAW) can be used to compare projects.
Equivalent Annual Cost (EAC) can be used instead of EAW if revenues are not included.
EAC = – EAW

4. Internal Rate of Return
Internal Rate of Return (IRR):
The interest rate i* at which NPW = 0
Note: This is the same as finding the roots of a polynomial equation. If there is more than one sign change in the net annual cash flows over the life of the project, then there is more than one internal rate of return (root)!
We may find the IRR by either the manual method we used for the bond yield, or we may use the computer to find the roots by either plots or numerical methods

5. IRR Example
Project A costs $10,000 and will last for 10 years. Annual, end of year revenues will be $3000, and expenses will be $ There is no salvage value.
Project B costs $20,000 and will also last for 10 years. Annual revenues will be $4000 with annual expenses of $ Salvage value is $14,500.
What is each project’s IRR?

6. Table Example i* (P/A, i*, 10) (P/F, i*, 10) 6% 7.3601 .5584 8% 6.7101
Engineering Economy
4/22/2017
Table Example i*
(P/A, i*, 10)
(P/F, i*, 10) 6%
7.3601
.5584 8%
6.7101
.4632
10%
6.1446
.3855
12%
5.6502
.3220
18%
4.4941
.1911
Copyright (c) , D.H. Jensen & K.D. Douglas

8. Internal Rate of Return
Example PW(i) = (P/A, i, 5) + 4(P/F, i, 5)
3,000 5
4,000
16,000

9. Internal Rate of Return
Example PW(i) = (P/A, i, 5) + 4(P/F, i, 5) i* = 5 1/4 % i* < MARR
3,000 5
4,000
16,000

10. Spreadsheet Example

11. IRR Problems Consider the following cash flow diagram. We
1,000
4,100
5,580
2,520 n 1 2 3
Consider the following
cash flow diagram. We
wish to find the Internal
Rate-of-Return (IRR).

12. IRR Problems Consider the following cash flow diagram. We
1,000
4,100
5,580
2,520 n 1 2 3
Consider the following
cash flow diagram. We
wish to find the Internal
Rate-of-Return (IRR).
PWR(i*) = PWC(i*)
4,100(1+i*)-1 + 2,520(1+i*)-3 = 1, ,580(1+i*)-2

13. IRR Problems NPV vs. Interest ($5) $0 $5 $10 $15 $20 $25 0% 10% 20%
30%
40%
50%
60%
Interest Rate
Net Present Value

14. Decisions with IRR
When applied to project selection among independent projects – i.e. there are enough funds such that any or all of the projects may be selected – then investing based on IRR is easy:
Select all projects with IRR > MARR!
Note: Make sure that there is only one IRR (root)!

15. Decisions with IRR
When applied to project selection among mutually exclusive projects – i.e. there is not enough money to do them all – IRR can produce the same result as NPW and EAW.
However, incremental analysis MUST be used!
REASON: IRR is a relative measure of project merit

16. Why Must Incremental Analysis be Used for Competing Projects?
Assume that an MARR of 16% per year is required, and $ is available to invest:
Project A requires $ upfront to obtain an IRR of 35% per year.
Project B requires an $ first cost and returns an IRR of 29% per year.
What could we do with the un-invested money from Project A? ($35 000)

17. Why Must Incremental Analysis be Used for Competing Projects?
It would be reasonable to invest the remaining $ at the MARR:
Overall IRRA = (.35) (.16)
85 000
= 27.2% per year
Project B returns an IRR of 29% per year on ALL the money available to invest.

18. Incremental Analysis
A technique or approach that can be used with NPW, EAW, and later with IRR and Cost/Benefit to determine if an incremental expenditure should be made.
Note: If using NPW or IRR, lifetimes must be equal – so use Least Common Multiple or Study Period!

19. Steps of the Process
Order alternatives from lowest to highest initial investment.
Let Alternative A0 (do nothing) be considered the current best.
Consider next Alternative ( j = j+ 1)
Determine cash flows for “current best” and Alternative j.
Determine incremental cash flows between “current best” and Alternative j.
Calculate PW, AW, FW, IRR (or Benefit/Cost)
of only the incremental cash flows.

20. Steps of the Process
If incremental investment yields NPW, EAW, or a NFW > 0*, then the new “current best” becomes Alternative j.
* (B/C ratio > 1, or IRR > MARR)
If there are remaining alternatives, go to Step 3.
If all alternatives have been considered, select the “current best” alternative as the preferred alternative.

21. Net Cash Flows for Alternatives A0 - A3
End of Year, t
A 0
A 1
A 2
A 3 $0
-$10000
-$50,000
-$75,000 1
4,500
20,000 2
25,000 3
30,000 4
35,000 5
40,000

22. IRR Incremental Analysis
Rank projects from lowest to highest initial cost
Eliminate any projects with IRR < MARR
Starting from the least expensive project to the next most expensive, justify each incremental investment
IRR HC-LC < MARR Accept LC Project
& Reject HC Project
IRR HC-LC = MARR Indifferent
IRR HC-LC > MARR Reject LC Project
& Accept HC Project