For a 2,000 kg an hour brass billet reheating furnace in Jamnagar, do the Bureau of Energy Efficiency reports favour an efficient oil furnace or a gas furnace?

On paper the Bureau of Energy Efficiency (BEE) Jamnagar efficient oil furnace pays back first, in 0.82 years at rupees (Rs) 11.55 lakh, against 1.15 years at Rs 18.70 lakh for gas. Gas cuts about 75 tonnes more carbon dioxide a year, and most of its extra yearly saving is a printed difference in blower power.

The two reports for the same furnace

• Both start from the same old furnace: 18% efficient, 37.03 litres of oil a tonne, 4,000 tonnes a year over 2,000 hours, 148,120 litres.
• Efficient oil furnace: 28% efficient, 23.26 litres a tonne, so 13.77 litres saved a tonne and 55,080 litres a year. Cost Rs 11.55 lakh (Rs 10.50 lakh plus Rs 1.05 lakh erection). Saving Rs 14.12 lakh a year, payback 0.82 years, net present value (NPV) Rs 40.51 lakh, internal rate of return (IRR) 94.45%.
• Gas furnace with waste heat recovery: 29% efficient, 26 normal cubic metres (Nm3) of gas a tonne, 104,000 Nm3 a year, no oil. Cost Rs 18.70 lakh (Rs 17.00 lakh plus Rs 1.70 lakh). Saving Rs 16.33 lakh a year, payback 1.15 years, NPV Rs 42.29 lakh, IRR 67.65%.

Per tonne of billets the fuel bills are almost level

At the reports' prices of Rs 28 a litre and Rs 24 a Nm3, the efficient oil furnace burns Rs 651 of oil a tonne (23.26 x 28) and the gas furnace Rs 624 (26 x 24). That is Rs 27 a tonne, or about Rs 1.09 lakh a year on 4,000 tonnes, in gas's favour (my arithmetic).

Why the yearly saving differs by Rs 2.21 lakh

• Fuel: about Rs 1.09 lakh, as above.
• Power: the oil report charges a 17.5 horsepower (HP) load, 13.05 kilowatts, so Rs 1.30 lakh a year at Rs 5 a kilowatt hour (kWh). The gas report charges a 2 HP blower, Rs 0.15 lakh. The difference is about Rs 1.15 lakh.
• Had the oil furnace been charged the gas furnace's Rs 0.15 lakh, its saving would be about Rs 15.27 lakh and payback 0.76 years (my arithmetic). Ask each maker for the connected load of the burner, blowers and pumps in writing; it decides this comparison.

Carbon dioxide (CO2) and the extra cost of gas

• Printed: 178 tonnes a year for oil and 253 for gas. The oil figure counts only the oil saved, at about 3.2 kilograms (kg) a litre, and neither subtracts power.
• On the 2.97 kg a litre our other Jamnagar pages use for furnace oil (an estimate) and the blower at 0.675 kg a kWh: efficient oil about 146 tonnes (163.6 less 26,100 kWh, 17.6), gas about 221 tonnes (439.9 less the report's 217 for gas and 2 for the blower).
• Gas costs Rs 7.15 lakh more for Rs 2.21 lakh a year more saving, about 3.2 years on the extra (my arithmetic), and removes about 75 tonnes more CO2 a year. It also ends oil purchases, where the efficient oil furnace still burns 93,040 litres a year.

Efficient oil furnace, report sums

• Oil saved: 13.77 litres x 4,000 tonnes = 55,080 litres. 55,080 x Rs 28 = Rs 15.42 lakh
• Less power: 13.05 kilowatts x 2,000 hours = 26,100 kWh x Rs 5 = Rs 1.30 lakh. Saving Rs 14.12 lakh
• Payback: Rs 11.55 lakh / Rs 14.12 lakh = 0.82 years
• Oil still burnt: 23.26 x 4,000 = 93,040 litres a year

Prices are the reports' own at 2010. The CO2 line is an estimate using an oil factor from our other Jamnagar pages.

What Senseible does here

Senseible reads oil invoices, gas bills and electricity bills into monthly records, so fuel and power per tonne of billets before and after a furnace change are on file. It does not size furnaces or check a maker's efficiency claim.

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Sources: BEE, Detailed project report: energy efficient oil fired reheating furnace, 2,000 kg, Jamnagar brass cluster (2010, SAMEEEKSHA), BEE, Detailed project report: energy efficient gas fired reheating furnace, 2,000 kg, Jamnagar brass cluster (2010, SAMEEEKSHA)

Last reviewed 2026-11-06. Report figures are from BEE's Small and Medium Enterprises (SME) programme project reports; costs, fuel prices and paybacks are at 2010 prices. Redo both paybacks with today's oil and gas prices and written quotes.