Which Bureau of Energy Efficiency Ganjam efficient motor report fits my rice mill main motor: 30, 40 or 50 horse power?

Three Bureau of Energy Efficiency (BEE) Ganjam reports replace a rice mill main motor of 30, 40 or 50 horse power (HP) for rupees (Rs) 0.56, 0.73 and 0.93 lakh. They save 5,273, 6,382 and 7,900 kilowatt hours (kWh) a year, with paybacks of 2.55, 2.70 and 2.82 years. The 50 HP report says 10 hours but calculates on 12.

The three reports side by side

• 30 HP (22 kilowatts, kW): motor made 1986, efficiency 81.1% old and 92.2% new. Measured draw 14.6 kW, new 12.84, saving 1.76 kW. Runs 10 hours x 300 days. 5,273 kWh, Rs 0.22 lakh a year. Cost Rs 0.56 lakh. Payback 2.55 years.
• 40 HP (30 kW): motor made 1990, 82.1% to 92.9%. Draw 18.3 kW, new 16.17, saving 2.13 kW. 10 hours x 300 days. 6,382 kWh, Rs 0.27 lakh. Cost Rs 0.73 lakh. 2.70 years.
• 50 HP (37.5 kW): year not given, 83.3% to 93.3%. Draw 21.18 kW, new 18.91, saving 2.27 kW. 12 hours x 290 days. 7,900 kWh, Rs 0.33 lakh. Cost Rs 0.93 lakh. 2.82 years.
• All three price power at Rs 4.20 a kWh, describe the motor as the main motor of a common shaft with belt drives at 1,440 revolutions a minute, and say installation needs about a week of process downtime.

Why the payback creeps up with size

The cost is about Rs 1,850 for each HP in all three reports, so the payback depends on the saving per HP. That falls: 0.059, 0.053 and 0.045 kW saved for each HP. The efficiency gain shrinks as the old motor gets better (11.1, 10.8 and 10.0 points), and, in my division of the measured draw by the rating (the reports print no loading), the motor is loaded less against its rating: 14.6 of 22 kW is 66%, 18.3 of 30 is 61% and 21.18 of 37.5 is 56%.

The saving is 12.1%, 11.6% and 10.7% of the measured draw. It follows the report's own formula: new draw = old draw x old efficiency / new efficiency, so 14.6 x 81.1 / 92.2 = 12.84 kW.

The 50 HP report contradicts itself on hours

The 30 and 40 HP reports run the motor 3,000 hours a year. The 50 HP report runs it 3,480. My own arithmetic on the printed figures: at 3,000 hours the 50 HP saving would be 2.27 x 3,000 = 6,810 kWh, Rs 0.29 lakh, and Rs 0.93 lakh / Rs 0.286 lakh gives 3.25 years, not 2.82. At 3,480 hours the 30 HP saving would be 6,125 kWh, Rs 0.26 lakh, and its payback 2.2 years.

So the order of paybacks is not only about motor size. Put in your own hours first.

• The 30 and 40 HP reports run the motor 10 hours x 300 days, 3,000 hours a year. The 50 HP body (section 1.4.1) also says the motor 'is operated for 10 hours in a day and 300 days', but its calculation (Annexure 3 and 5) uses 12 hours x 290 days, 3,480 hours, taken from the first row of its table of three mills.
• My arithmetic on the printed figures: at 3,000 hours the 50 HP saving would be 2.27 x 3,000 = 6,810 kWh, Rs 0.29 lakh, and Rs 0.93 lakh / Rs 0.286 lakh gives 3.25 years, not 2.82. At 3,480 hours the 30 HP saving would be 6,125 kWh, Rs 0.26 lakh, and its payback 2.2 years.
• So the order of paybacks is not only about motor size. Put in your own hours first.

Printed figures to treat with care

• The kWh a year are the kW saved times hours, to within rounding: 1.76 x 3,000 = 5,280 against 5,273 printed, and 2.13 x 3,000 = 6,390 against 6,382.
• Carbon dioxide (CO2): the reports print 4, 5 and 6 tonnes a year and no factor. At the grid factor of 0.675 kilograms (kg) CO2 a kWh for financial year (FY) 2025-26, the same savings are about 3.6, 4.3 and 5.3 tonnes.
• Each existing-motor efficiency is the report's estimate for one named mill, not a reading: Annexure 1 takes the initial efficiency (91.1, 92.1 and 92.3%) and subtracts 1 point for every rewind (10, 10 and 9 rewinds), giving 81.1, 82.1 and 83.3%. The annexures list other mills at 82.3 to 84.7%.
• The summary table lists process downtime as 6 days; the text of each report says one week.
• 50 HP hours: the body says 10 hours x 300 days, while Annexure 3 and 5 calculate on 12 hours x 290 days.

Before you order

• Read your own motor for a normal day: kW drawn and hours run. Use the report's formula with your figures.
• Ask the maker for the guaranteed efficiency at your load. My division of the measured draw by the rating gives 56 to 66% for these motors.
• Check the motor's age and whether it has been rewound. A newer, better motor saves less than the 10 to 11 points printed here.

The 50 HP report as printed, then at 3,000 hours

• Draw 21.18 kW x 83.3 / 93.3 = 18.91 kW. Saving 2.27 kW
• 2.27 x 12 hours x 290 days = 7,900 kWh x Rs 4.20 = Rs 33,180, printed as Rs 0.33 lakh. Rs 0.93 lakh / 0.33 = 2.82 years
• My reading at 3,000 hours: 2.27 x 3,000 = 6,810 kWh x Rs 4.20 = Rs 28,602
• Rs 0.93 lakh / Rs 0.286 lakh = about 3.25 years

First two lines are the report's own. The last two are an example of my own reading, using the report's inputs.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so your monthly units are on file next to a report's yearly kWh. A bill covers the whole mill, so the motor's own draw still needs a meter. The green loan check shows what a lender asks for.

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Sources: BEE, Detailed project report: energy efficient motor 30 HP, Ganjam rice mill cluster (SAMEEEKSHA), BEE, Detailed project report: energy efficient motor 40 HP, Ganjam rice mill cluster (SAMEEEKSHA), BEE, Detailed project report: energy efficient motor 50 HP, Ganjam rice mill cluster (SAMEEEKSHA), Central Electricity Authority (CEA), CO2 Baseline Database for the Indian Power Sector

Last reviewed 2026-11-05. Report figures are from BEE's Small and Medium Enterprises (SME) programme project reports of 2010, at a Rs 4.20 a kWh tariff. Check today's tariff, a current quote and your own motor readings before you rely on the payback.