How much does an efficient motor save on a dairy ammonia compressor?

Bureau of Energy Efficiency (BEE)'s Gujarat dairy reports swap a motor of 87 to 87.5% efficiency for one at 94.5 to 95.4%. Savings are 15,257 kWh a year at 30 kW, 29,096 at 55 kW and 34,522 at 75 kW. The 55 kW sum only works at 20 hours a day, not the 16 the report lists.

The three cases

• 30 kW: measured 26.7 kW, saving 2.12 kW, 15,257 kWh a year, cost Rs 1.86 lakh, payback 2.05 years. Existing motor 87% efficient; the report says many motors in the cluster have been rewound 2 to 3 times.
• 55 kW: measured 48.8 kW, saving 4.04 kW, 29,096 kWh a year, cost Rs 2.42 lakh, payback 1.39 years.
• 75 kW: measured 57.9 kW, saving 4.79 kW, 34,522 kWh a year, cost Rs 3.79 lakh, payback 1.87 years.

How the saving is found

The same load is delivered by a more efficient motor, so the power drawn falls in proportion to the efficiency ratio. For the 30 kW case that is 26.7 x (1 minus 0.87 / 0.945) = 2.12 kW. The report's text says up to 5% for such a swap, but its own table works out at 7.9% for the 30 kW motor and 8.3% for the other two.

The 55 kW case needs checking

The report lists 16 hours a day for the 55 kW compressor, yet 4.04 kW over 360 days at 20 hours gives 29,096 kWh, the figure it uses. At 16 hours the saving is 23,277 kWh, worth Rs 1.39 lakh, and the payback is 1.74 years, not 1.39. Both are still good, but know which hours are real for your plant.

Rewinding

The report warns that old motors rewound many times lose efficiency, and recommends standard rewinding practice with standard material where a rewind is unavoidable.

The sums

• 30 kW: 2.119 x 20 x 360 = 15,257 kWh. At Rs 5.96 = Rs 90,933. 1.86 lakh / 90,933 = 2.05 years
• 55 kW at 20 hours: 4.041 x 7,200 = 29,096 kWh. At Rs 5.98 = Rs 1.74 lakh. 2.42 / 1.74 = 1.39 years
• 55 kW at 16 hours: 4.041 x 16 x 360 = 23,277 kWh. At Rs 5.98 = Rs 1.39 lakh. 2.42 / 1.39 = 1.74 years
• 75 kW: 4.795 x 7,200 = 34,522 kWh. At Rs 5.86 = Rs 2.02 lakh. 3.79 / 2.02 = 1.87 years
• CO2 at 0.675 kg a kWh (Central Electricity Authority (CEA), financial year (FY) 2025-26): 15,257 x 0.675 = 10.3 tonnes (t), 29,096 x 0.675 = 19.6 t, 34,522 x 0.675 = 23.3 t

Report figures at the report's tariffs. Each case is one compressor motor.

What Senseible does here

Senseible reads electricity bills into monthly kWh and carbon dioxide equivalent (CO2e) at the grid factor for the bill's financial year, so a saving shows in later bills. Motor efficiency and loading are for your own tests; a plant bill covers everything on the meter.

• Green loan readiness check
• Soft starters on the same compressors
• IE2 to IE4 motor replacement savings
• Gujarat chilling centres: energy and carbon

Sources: BEE, Detailed project reports: energy efficient motor 30 kW, 55 kW and 75 kW, Gujarat dairy cluster (2010, SAMEEEKSHA), BEE, Detailed project report: energy efficient motor 30 kW, Gujarat dairy cluster (2010, SAMEEEKSHA), BEE, Detailed project report: energy efficient motor 75 kW, Gujarat dairy cluster (2010, SAMEEEKSHA), CEA CO2 Baseline Database, version 22.0

Last reviewed 2026-11-04. Report figures are from a BEE SME programme project report; costs and paybacks are at the report year's prices. Check today's prices and a current quote before you rely on the payback. Re-check the grid factor when CEA publishes a new edition.