How much power does a VFD save on a ceramic grinding machine?
About 15% of the grinding section's power in BEE's Morbi report: 66,047 kWh a year on a wall tile plant whose ball mills and blungers use 440,310 kWh. That is about 45 t CO2 on today's grid. Cost Rs 4.64 lakh, saving Rs 2.54 lakh a year, payback 1.82 years at 2010 prices.
Why grinding motors overspend
A ball mill or blunger batch runs 5 to 6 hours for body slip and 12 to 14 hours for glaze. The motor needs full speed at the start, but its load falls as the slurry evens out, and it keeps turning at full speed anyway. In the audited plant, blunger motors of 7.5 kW drew between 35% and 77% of rating, with efficiency falling from about 80% to 64% at the light end.
What the VFD does
- Runs the main motor at full speed at the start of each batch, then slows it on a timed programme as the slurry becomes uniform.
- Applies to body ball mills, blungers and the glaze ball mill.
- Mills run in rotation, so drives go in one machine at a time with no stoppage.
- Less wear on belts and liners at the slower speed, according to the report.
The plant in the report
- Wall tiles, about 4,044 m2 a day, 1,254,228 kWh a year in all.
- Grinding uses 440,310 kWh, about 35% of the plant's power, over 330 days at 24 hours.
- Saving: 15% = 66,047 kWh a year, worth Rs 2.54 lakh at Rs 3.85 a kWh.
- Cost: VFDs Rs 3.63 lakh, erection Rs 0.36 lakh, tax, interest and other costs about Rs 0.64 lakh, Rs 4.64 lakh in total.
Prove it on one mill first
The 15% is a cluster rule of thumb, not a measurement on this plant. Put an energy meter on one mill, log kWh per batch for two weeks, fit the drive, and log the same batch recipe again. Check the residue on sieve too: slower running can stretch the batch, which eats the saving.
One wall tile plant, one year (estimate)
- Grinding power: 440,310 kWh x 15% = 66,047 kWh saved
- CO2: 66,047 x 0.675 = 44.6 t
- The report's 52 t uses an older grid factor of about 0.79
- Payback: 4.64 / 2.54 = 1.83 years; the report rounds to 1.82
CO2 at CEA's FY 2025-26 grid factor of 0.675 kg per kWh.
What Senseible does here
Senseible reads monthly electricity bills into kWh and CO2 records tied to each bill. Pair them with a meter on the grinding feeder and the saving from the drives is easy to show a lender or buyer.
- Green loan readiness check
- Tile plant slip agitators: power saved
- VFD on a tile hydraulic press
- Vitrified tile polishing line power
Sources: BEE, Detailed project report: variable frequency drives on grinding machine, Morbi ceramic cluster (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 the report year's prices. Check today's tariff and a current drive quote.