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

Canonical: https://senseible.earth/answers/cnc-grinding-machine-electricity-saving

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](https://senseible.earth/green-loan-check)
- [Bangalore machine tool units: grid power](https://senseible.earth/answers/bangalore-machine-tool-units-grid-power-saving)
- [CNC lathes against conventional lathes](https://senseible.earth/answers/cnc-lathe-replacing-conventional-lathes-kwh)
- [Emissions fell but intensity rose](https://senseible.earth/answers/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)](https://sameeeksha.org/pdf/dpr/Bangalore_machine_tools_cluster/Replacement_of_conventional_grinding_machine_to_CNC_grinding_machine_BNG_MTC.pdf), [CEA CO2 Baseline Database, version 22.0](https://cea.nic.in/cdm-co2-baseline-view?mappingId=234&lang=en)

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.