Why does the 36 kW electric bogie annealing furnace in the Bureau of Energy Efficiency Jagadhri reports use more power per tonne of brass than the 60 kW one?

In the two Bureau of Energy Efficiency (BEE) Jagadhri reports, both furnaces anneal 1,200 tonnes of brass a year in place of wood. The 36 kilowatt furnace takes 120 kilowatt hours (kWh) a tonne and the 60 kilowatt one 100, so it costs rupees (Rs) 2.5 lakh less but saves Rs 1.09 lakh a year less.

The two reports side by side

• 36 kilowatt (kW) furnace: 2,000 kilograms (kg) a batch, 6 hours a batch, 2 batches a day, 240 kWh a batch. Cost Rs 6.75 lakh (Rs 6.25 lakh furnace plus Rs 0.50 lakh civil work and erection). Saving Rs 288 a tonne, Rs 3.46 lakh a year, payback 1.95 years, net present value (NPV) Rs 5.93 lakh, internal rate of return (IRR) 33.89%.
• 60 kW furnace: 4,000 kg a batch, 8 hours a batch, 1 batch a day, 400 kWh a batch. Cost Rs 9.25 lakh (Rs 8.75 lakh plus Rs 0.50 lakh). Saving Rs 379 a tonne, Rs 4.55 lakh a year, payback 2.03 years, NPV Rs 7.38 lakh, IRR 31.85%.
• Both: 300 days a year and 1,200 tonnes of brass, wood at Rs 4.5 a kg, electricity at Rs 4.5 a kWh. Two weeks of downtime.

Why the smaller furnace uses more power per tonne

• The old wood furnace uses the same wood per tonne in both reports: 368 kg for 2,000 kg and 737 kg for 4,000 kg, about 184 kg a tonne. Yearly wood is 220.8 and 221.1 tonnes because 600 small batches or 300 large ones make the same 1,200 tonnes (my arithmetic).
• The electric furnace is the difference: 240 kWh for 2,000 kg is 120 kWh a tonne; 400 kWh for 4,000 kg is 100. So yearly power is 144,000 against 120,000 kWh.
• Wood per batch costs Rs 1,656 and Rs 3,316. Electricity per batch costs Rs 1,080 and Rs 1,800. The savings are Rs 576 a batch and Rs 1,516 a batch. The 36 kW report's table heads its Rs 1,080 line per tonne, but it is per 2,000 kg batch.

When the saving disappears

The saving exists only while electricity costs less than the wood it replaces. At the report's wood price, the 36 kW furnace stops saving at Rs 6.90 a kWh (Rs 1,656 / 240) and the 60 kW at Rs 8.29 (Rs 3,316 / 400). That is my arithmetic. Put your own wood price per kg and your tariff per kWh from last month's bills into those two sums before you decide. Then compare the furnace's connected load, 36 or 60 kW, with your sanctioned load.

Carbon dioxide (CO2): fossil goes up

• The reports count wood CO2 as saved, at 1.64 kg of CO2 a kg of wood (362.38 and 362.60 tonnes), and grid power at 0.81 kg a kWh (116.64 and 97.20 tonnes). Printed net cuts are 245.74 and 265.40 tonnes.
• Wood is biomass, so its CO2 is normally reported on its own line rather than netted against grid power, as our 60 kW page explains. On that basis the swap adds fossil CO2 from the grid: 144,000 x 0.675 = 97.2 tonnes a year for the 36 kW furnace, 120,000 x 0.675 = 81.0 tonnes for the 60 kW, using the Central Electricity Authority (CEA) FY 2025-26 factor. That is 81 and 67.5 kg per tonne of brass.
• The case for either furnace is cost, quality and working conditions, not fossil CO2.

The 36 kW furnace, report sums

• Wood per batch: 368 kg x Rs 4.5 = Rs 1,656. Electricity per batch: 240 kWh x Rs 4.5 = Rs 1,080. Saving Rs 576 a batch, Rs 288 a tonne
• Year: 2 batches x 300 days = 600 batches x Rs 576 = Rs 3.46 lakh. Payback Rs 6.75 lakh / Rs 3.46 lakh = 1.95 years
• Power: 600 x 240 = 144,000 kWh x 0.675 = 97.2 tonnes of fossil CO2 a year added, against 220.8 tonnes of wood no longer burnt

Prices are the reports' own, at 2010 levels. The grid factor is CEA's FY 2025-26 figure; the report used 0.81.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so wood bought, power drawn and brass annealed can be set side by side before and after a switch. It does not size furnaces or confirm a maker's figures.

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• Jagadhri brass and aluminium cluster footprint

Sources: BEE, Detailed project report: bogie brass annealing furnace, 36 kW, Jagadhri brass and aluminium cluster (SAMEEEKSHA), BEE, Detailed project report: bogie brass annealing furnace, 60 kW, Jagadhri brass and aluminium cluster (SAMEEEKSHA), Central Electricity Authority (CEA), CO2 Baseline Database, version 22.0

Last reviewed 2026-11-06. Report figures are from BEE's Small and Medium Enterprises (SME) programme project reports; costs, wood and power prices and paybacks are at the report year's prices. Redo the sums with today's wood price and tariff and a current quote.