How much power does a lid on an induction furnace crucible save?

About 20 kWh per tonne melted. An open crucible loses about 40 kWh per tonne as radiation, and a swing lid stops about half of it, by TERI's costing for Bokaro foundries. At 600 to 1,000 kWh per tonne that is 2 to 3% of the melt's power.

Why the open mouth costs you

Bokaro's foundries melt in crucibles of 300 to 1,000 kg and keep the mouth open through the heat. TERI puts the radiation loss at 5 to 8% of the energy. Large scrap pieces make it worse: the crucible fills poorly, the heat runs longer and the mouth stays open longer.

Two fixes, two figures

• Swing lid on the crucible: 20 kWh per tonne, half the 40 kWh radiation loss.
• Metal cutter to size the scrap: fuller charges and shorter heats.
• Together: 30 to 50 kWh per tonne in TERI's table, against 600 to 1,000 kWh per tonne melted.
• The profile's text says a lid alone saves 3 to 5%; its table gives the 20 kWh figure, which we use.

Measure it on your own furnace

1. Log kWh from the furnace panel meter and tonnes tapped for every heat for two weeks with the lid open as usual.
2. Fit the lid and log two more weeks on the same grades of scrap.
3. Compare kWh per tonne, not monthly bills, so a busy month does not look like a saving.
4. Keep both logs: a lender or buyer asking what the change saved will want the before figure.

Payback

TERI priced the lid and cutter at Rs 5,00,000 and the saving at Rs 3,30,000 a year at 100 t a month, payback 1.5 years by its table, though its text says within a year. A foundry melting less, or saving only the lid's 20 kWh, should expect longer.

A 100 t a month foundry (estimate)

• Lid alone: 20 kWh x 1,200 t = 24,000 kWh a year x 0.675 kg = 16.2 t CO2
• Lid and cutter at 50 kWh per tonne: 60,000 kWh = 40.5 t CO2, TERI's annual figure
• At Rs 7.5 per kWh, the HT rate in the profile: lid alone about Rs 1.8 lakh a year
• Whole melt at 800 kWh per tonne: 960,000 kWh = 648 t CO2, so the lid trims about 2.5%

Crucible sizes, losses, savings and costs from TERI's Bokaro Industrial Area profile (2021). TERI's 60,000 kWh a year matches 50 kWh per tonne on 1,200 t, the top of the combined range. CO2 at the CEA FY 2025-26 grid factor.

What Senseible does here

The green loan check shows what a lender asks before funding furnace upgrades; Senseible reads your electricity bills into monthly kWh and CO2, so the before and after sit on record.

• Green loan check
• Induction furnace kWh per tonne
• Bokaro industrial area energy

Sources: TERI, Bokaro Industrial Area cluster profile (2021).docx), CEA, CO2 Baseline Database for the Indian Power Sector, version 22.0

Last reviewed 2026-10-31.