Energy saving calculation for chiller replacement

A company has a 500 KW reciprocating chiller. The company engineer has determined that the efficiency (COP) of this machine is 2. He is considering the installation of a new 500 KW centrifugal chiller with a COP of 5. The chiller cost, including installation is estimated to be Rs. 5000000. Energy costs are 500/KW-monthly demand and Rs. 5/KWh. If the unit is operated 2500 hours for six months out of the year, calculate the simple payback.

Kw elec input old = 500KW/2 =250

Kw elec input new = 500KW/5 = 100

KW elec Savings = 250 KW - 100 KW = 150 KW

Kwh savings = 150 Kw x 2500 hrs/yr = 375000 Kwh/year

Rs/Year savings = Rs. 150 KW x 500/KW-monthly x 6 months/Year + Rs. 5/Kwh x 375000 Kwh/Year

Rs/Year savings = 6375000

Simple Payback period = 8000000/6375000 = 1.25 Yrs

Chiller COP and Size range in KW

Chiller COP and Size range in KW

Compressor(Electric Driven)                     COP                   Size Range(KW)

Water Cooled chiller

Reciprocating chiller                                    3.5 to 4.5                        10 to 1500

Centrifugal  chiller                                        4.0 to 7.0                        300 to >30000

Screw chiller                                                5.0 to 6.0                        200 to 5000

Air Cooled chiller

Reciprocating chiller                                    2.2 to 3.5                        10 to 1600

Centrifugal  chiller                                        3.5 to5.0                        300 to >10000

Screw chiller                                               3.0 to 5.0                        200 to 1800

Scroll chiller                                                2.5 to 4.0                        10 to 200