Why do the Bureau of Energy Efficiency (BEE) Surat reports show a new 6 or 7 chamber stenter paying back in 2.5 to 2.6 years?

BEE's Surat reports price a new 6 chamber stenter at rupees (Rs) 56.56 lakh and a 7 chamber one at Rs 60.60 lakh. They save 403,200 and 412,608 kilowatt hours (kWh) a year, worth Rs 22.58 and 23.11 lakh, so payback is printed as 2.5 and 2.6 years.

The two reports side by side

• 6 chamber: the old machine draws 130 kilowatts (kW) on a connected load of 156 kW. The new one draws 82 kW on 117 kW. Saving: 48 kW x 24 hours x 350 days = 403,200 kWh. At Rs 5.60 a kWh that is Rs 22.58 lakh. Cost: Rs 56.00 lakh plus Rs 0.56 lakh to erect, Rs 56.56 lakh. Printed payback 2.50 years, internal rate of return (IRR) 22.48%, net present value (NPV) Rs 24.84 lakh.
• 7 chamber: the old machine draws 140 kW on 173 kW connected. The new one draws 90.88 kW on 136 kW. Saving: 49.12 kW x 8,400 hours = 412,608 kWh, Rs 23.11 lakh. Cost: Rs 60.00 lakh plus Rs 0.60 lakh, Rs 60.60 lakh. Printed payback 2.6 years, IRR 20.34%, NPV Rs 21.96 lakh.
• Both count electricity only. Each says gas may be saved by the better design, but the supplier does not guarantee it, so no gas saving is counted. The stenters in these reports are gas heated, so any gas saving would be on top.
• Both assume a 24 hour day, 350 days, a 3 to 1 debt to equity split, a 10% loan, two weeks of downtime and eight weeks to finish.

Where the printed figures wobble

• The saving is described in percent three ways. The 6 chamber text says 37% in one place and 36% in another; 48 / 130 = 36.9%. The 7 chamber text says 35% in the body and 36% in the annexure; 49.12 / 140 = 35.1%.
• The 7 chamber body says the new machine takes 90 kW and saves 50 kW, but the annexure uses 90.88 and 49.12. The saving of 412,608 kWh is built on the annexure figures.
• Both bodies say the old machine uses 130 or 140 kWh "per day" for 24 hours. The sums only work as kW: 130 x 24 x 350 = 1,092,000 kWh a year, and 140 x 24 x 350 = 1,176,000.
• The 6 chamber financial annexure lists the installed capacity as 50,000 metres a day, but the body and Table 1.2 use 80,000. The 7 chamber says 100,000 in both places.

Per metre of cloth

The 6 chamber table lists two units at 0.039 and 0.038 kWh a metre on 80,000 metres a day, and a third at 0.039 on 70,000. The printed row for Vitrag Silk Mills is 2,304 kWh a day on 80,000 metres, which is 0.0288 a metre, not the 0.038 printed beside it. Another figure that does not tie: the 6 chamber summary prints a net present value of Rs 24.84 lakh, but its financial annexure prints 24.48. The new machine at 82 kW is 82 x 24 / 80,000 = 0.0246 kWh a metre, our division.

The 7 chamber table lists 39.0 and 37.5 kWh per 1,000 metres for two units. Its annexure baseline is lower, 140 x 24 / 100,000 = 33.6, and the new machine is 90.88 x 24 / 100,000 = 21.8. Our reading: a unit like those two audited ones would see a wider gap than the annexure shows, if the new machine does what the report says.

The carbon dioxide (CO2) lines

The reports print 342 and 350 tonnes a year and no factor. Dividing, both come to 0.848 kilograms (kg) of CO2 a kWh. The Surat steam turbine reports from the same programme print 0.85 tonne of CO2 a megawatt hour, so that is probably the factor, our reading.

At the Central Electricity Authority (CEA) factor for financial year (FY) 2025-26, 0.675 kg a kWh, the same kWh give 272.2 and 278.5 tonnes. At 0.710 for FY 2024-25 they give 286.3 and 293.0. Use the factor for the year of your own bills.

Before you order

• Put your stenter's kWh a day and metres a day side by side for a month. That ratio, not the report's, is your baseline.
• Ask the maker to guarantee kW at your metres a day, and to say in writing what happens to gas use.
• Rework the saving at your own tariff: kWh saved x your rate. Rs 5.60 is a 2010 figure.

The 6 chamber arithmetic, step by step

• Old: 130 kW x 24 x 350 = 1,092,000 kWh a year
• New: 82 kW x 24 x 350 = 688,800 kWh a year
• Saved: 403,200 kWh x Rs 5.60 = Rs 22.58 lakh
• Payback: Rs 56.56 lakh / Rs 22.58 lakh = 2.50 years
• CO2 at 0.675: 403,200 x 0.675 = 272.2 tonnes, against 342 printed

Figures are the report's own at the report year's prices. The 0.675 is the CEA version 22.0 factor for FY 2025-26, an estimate of today's saving.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so your stenter's power and gas bills are on file to test a report's baseline against. It does not know your metres a day; that comes from your production book.

• Green loan readiness check
• Stenter fuel and CO2 per metre of fabric
• Surat 3 and 4 tonne boiler reports compared
• Old report CO2 versus today's grid factor

Sources: BEE, Detailed project report: stenter machine (6 chamber), Surat textile cluster (SAMEEEKSHA), BEE, Detailed project report: stenter machine (7 chamber), Surat textile cluster (SAMEEEKSHA), BEE, Detailed project report: energy conservation turbine (60 kW), Surat (SAMEEEKSHA), for the 0.85 tonne per MWh factor, Central Electricity Authority (CEA), CO2 Baseline Database for the Indian Power Sector

Last reviewed 2026-11-05. Report figures are from BEE's Small and Medium Enterprises (SME) programme project reports, dated 2010, with electricity at Rs 5.60 a kWh. Check your tariff, a current quote and the gas bill before you rely on the payback.