Does replacing a conventional grinder with a CNC grinding machine save electricity?

Per tonne, yes: BEE's Bangalore report takes grinding from 975 to 750 kWh a tonne, which it counts as 51,384 kWh a year. But it also assumes output rises 1.75 times, so the unit's bill goes up by about 44,000 kWh. Electricity is under a tenth of the Rs 33.73 lakh benefit claimed.

The unit in the report

• 130.5 t of ground work a year on 127,212 kWh of grid power and no diesel: 975 kWh a tonne.
• Cost per tonne: Rs 4,875 of power, Rs 35,000 lost to rejected parts, Rs 11,350 of labour and utilities.
• Proposed: a CNC grinder at 750 kWh a tonne, with rejection falling to Rs 22,136 a tonne, and output rising 1.75 times to 228.4 t a year.
• Cost: Rs 42.41 lakh machine, Rs 0.50 lakh civil work, Rs 2.70 lakh installation: Rs 45.61 lakh.

Where the Rs 33.73 lakh comes from

• Saving per tonne: Rs 14,770, applied to 228.4 t.
• Rejection: Rs 12,864 a tonne, 87% of it.
• Electricity: 225 kWh x Rs 5 = Rs 1,125 a tonne, 8%, or Rs 2.57 lakh a year.
• Labour and utilities: Rs 781 a tonne, the rest.
• Payback 1.35 years overall. On electricity alone it would be about 18 years.

What your electricity bill will show

The 51,384 kWh is the power you avoid compared with making 228 t on the old grinders. Your meter compares this year with last: 127,212 kWh before, 171,281 kWh after at 750 kWh a tonne. Emissions per tonne fall by a quarter; the unit's total rises by a third. Report both, with tonnes made each month, or a buyer or lender comparing bills will think the project failed.

For the loan file

Lead with scrap and output, which carry the payback, and show kWh per tonne as the energy case. Keep a month of rejection records and production logs from the old machine, so the after figures have something to stand against.

Grid CO2 before and after

• Before: 127,212 kWh x 0.675 = 85.9 t for 130.5 t, 658 kg a tonne
• After: 171,281 kWh x 0.675 = 115.6 t for 228.4 t, 506 kg a tonne
• Avoided against old machines at the new output: 51,384 x 0.675 = 34.7 t
• The report says 38.54 t, on an older grid factor

Grid at CEA's FY 2025-26 factor, an estimate.

What Senseible does here

Senseible reads your electricity bills into monthly records linked to each bill, with CO2 by the CEA factor for the bill's year; add tonnes made to show the per tonne figure. Run the green loan check before you meet the bank about the machine.

• Green loan readiness check
• Bangalore machine tool units: grid power
• CNC lathes against conventional lathes
• Emissions fell but intensity rose

Sources: BEE, Detailed project report: replacement of conventional grinding machine with CNC grinding machine, Bangalore machine tools cluster (2010, SAMEEEKSHA), CEA CO2 Baseline Database, version 22.0

Last reviewed 2026-11-01. Report figures are from a BEE SME programme project report; costs and paybacks are at 2010 prices. Check a current quote and your own scrap rate.