How much does a variable frequency drive save on a 75 or 150 horse power ice plant compressor in the Bureau of Energy Efficiency Bhimavaram reports?

In Bureau of Energy Efficiency (BEE) Bhimavaram reports, a variable frequency drive (VFD) on a 75 horse power (HP) ice plant compressor saves 17,150 kilowatt hours (kWh) a year for rupees (Rs) 1.86 lakh, and on a 150 HP compressor 32,690 kWh for Rs 3.10 lakh. Payback is 2.91 and 2.52 years.

The two new reports

• 75 HP, a 55.95 kilowatt (kW) motor: 54.4 kW at full load, 29.9 kW with one cylinder working, 24.5 kW less. 2 part-load hours a day, 350 days: 49 kWh a day, 17,150 kWh a year, Rs 0.64 lakh at Rs 3.75 a kWh. Cost Rs 1.86 lakh, payback 2.91 years. Report carbon dioxide (CO2): 13 tonnes.
• 150 HP: 103.7 kW at full load, 57 kW part load, 46.7 kW less. 93.4 kWh a day, 32,690 kWh a year, Rs 1.23 lakh. Cost Rs 3.10 lakh, payback 2.52 years. Report CO2: 26 tonnes.
• The 60 HP report, covered on another page, gives 37.1 and 20.4 kW, 11,690 kWh and 3.61 years.

The same cut in every size

Part-load power is 55% of full-load power in all three: 20.4 / 37.1, 29.9 / 54.4 and 57 / 103.7. So the drive saves about 45% of the compressor's power during those hours whatever its size. The yearly saving then grows with motor size, and the price per horse power falls: about Rs 2,650 at 60 HP, Rs 2,480 at 75 and Rs 2,070 at 150. That is the whole reason payback improves from 3.61 to 2.91 to 2.52 years.

The two hours are an assumption

Each report counts 2 hours a day at part load and says the power figures are measured at full load and with only one cylinder working. How long your compressor really sits at part load is the number to find. Each extra hour a day is worth 8,575 kWh a year at 75 HP and 16,345 kWh at 150 HP. At 4 hours a day the 75 HP payback would be about 1.45 years. At 1 hour a day it would be about 5.8 years.

Before you buy

1. Clamp-meter the compressor motor at full load and with cylinders unloaded.
2. Log part-load hours for two weeks.
3. Ask for the drive supplier's saving at your own part-load kW, in writing.

75 HP report, rechecked, with carbon dioxide (estimate)

• Power cut at part load: 54.4 minus 29.9 = 24.5 kW
• Year: 24.5 x 2 hours x 350 days = 17,150 kWh; x Rs 3.75 = Rs 0.64 lakh
• Payback: Rs 1.86 lakh / Rs 0.64 lakh = 2.91 years
• CO2: 17,150 x 0.675 = 11.6 tonnes a year; the report's 13 implies about 0.76 kilograms a kWh
• 150 HP: 32,690 x 0.675 = 22.1 tonnes; the report says 26

Grid factor 0.675 kilograms of CO2 a kWh, Central Electricity Authority financial year 2025-26, an estimate.

What Senseible does here

Senseible reads electricity bills into monthly kWh, so months before and after a drive can be compared. The bill shows the whole plant, not one compressor, so the part-load hours need a meter or a log alongside.

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• Drive on an ice plant compressor, 60 HP
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Sources: BEE, Detailed project report: VFD for compressor motor, 60 HP, Bhimavaram (SAMEEEKSHA), BEE, Detailed project report: VFD for compressor motor, 75 HP, Bhimavaram (SAMEEEKSHA), BEE, Detailed project report: VFD for compressor motor, 150 HP, Bhimavaram (SAMEEEKSHA), CEA, CO2 Baseline Database for the Indian Power Sector

Last reviewed 2026-11-04. Report figures are from BEE's Small and Medium Enterprises (SME) programme project reports; costs, tariffs and paybacks are at the report year's prices. Check today's prices and a current quote before you rely on the payback.