In: Economics
| Thickness | Installation Cost | annual savings | Maintenance once in each 2 years | 
| 2cm | 217000 | 68000 | 4600 | 
| 5cm | 446000 | 125000 | 0 | 
Useful lives of both alternatives are 10 years. Find the best alternative using discounted payback period when MARR= %13 per year
Take the case when thickness is 2 cm
Following schedule can be generated
| Year , n | Cash Flow, CF | Discounted cash flow, DCF= CF/(1+13%)^n | Cumulative discounted cash flow | 
| 0 | -217000 | -217000.00 | -217000.00 | 
| 1 | 68000 | 60176.99 | -156823.01 | 
| 2 | 63400 | 49651.50 | -107171.51 | 
| 3 | 68000 | 47127.41 | -60044.10 | 
| 4 | 63400 | 38884.41 | -21159.69 | 
| 5 | 68000 | 36907.68 | 15747.98 | 
| 6 | 63400 | 30452.19 | 46200.18 | 
| 7 | 68000 | 28904.12 | 75104.30 | 
| 8 | 63400 | 23848.54 | 98952.84 | 
| 9 | 68000 | 22636.17 | 121589.01 | 
| 10 | 63400 | 18676.90 | 140265.91 | 
Discounted payback period in case when thickness is 2
cm=4+21159.69/36907.68=4.57 years
Now consider
Take the case when thickness is 5 cm
Following schedule can be generated
| Year , n | Cash Flow, CF | Discounted cash flow, DCF= CF/(1+13%)^n | Cumulative discounted cash flow | 
| 0 | -446000 | -446000.00 | -446000.00 | 
| 1 | 125000 | 110619.47 | -335380.53 | 
| 2 | 125000 | 97893.34 | -237487.20 | 
| 3 | 125000 | 86631.27 | -150855.93 | 
| 4 | 125000 | 76664.84 | -74191.08 | 
| 5 | 125000 | 67844.99 | -6346.09 | 
| 6 | 125000 | 60039.82 | 53693.72 | 
| 7 | 125000 | 53132.58 | 106826.30 | 
| 8 | 125000 | 47019.98 | 153846.29 | 
| 9 | 125000 | 41610.60 | 195456.89 | 
| 10 | 125000 | 36823.54 | 232280.43 | 
Discounted payback period in case when thickness is 5 cm=5+6346.09/60039.82=5.11 years
Discounted payback period is lower in case thickness is 2 cm. It should be selected.