What does the Tiruppur manual's improved chulha save for one unit and for all 56, and do the totals add up?

The Bureau of Energy Efficiency (BEE) Tiruppur manual lifts a bleaching chulha from 15% to 30% efficiency, halving 45 tonnes of wood to about 22 tonnes a year for rupees (Rs) 25,000. Across 56 chulhas it books 1,232 tonnes and Rs 36.96 lakh (1 lakh = 100,000). Per unit it uses Rs 3,600 a tonne; for the total, Rs 3,000.

Why a chulha is only 15% efficient

• The test: 1,500 litres heated from 30 to 90 degrees Celsius (C) is 90,000 kilocalories (kcal) of heat output. Firewood used 150 kilograms (kg) at 4,000 kcal a kilogram is 600,000 kcal in. 90,000 / 600,000 = 15%.
• Bleaching 200 kilograms of yarn a day takes 150 kilograms of wood, 0.75 kilograms of wood for each kilogram of yarn.
• The manual lists the causes: no air circulation or smoke removal, heat lost through the grate openings, no control on air supply, radiation from all sides and no monitoring of wood feeding.

The saving for one unit

The improved design, developed by Winrock International India, has a damper, an optimised furnace area, a better grate, use of heat in the flue gas and a chimney, and the manual puts its efficiency at around 30%. Wood falls by 1 minus 15/30 = 50%.

Present wood 45 tonnes a year (150 kilograms a day, which implies 300 days). Saved: 22.5 tonnes, printed as 22. Money printed: Rs 81,000, which is 22.5 x Rs 3,600. Investment Rs 25,000, payback 25,000 / 81,000 = 0.31 years, about 3.7 months, printed as 4.

The 56 unit total, and why it differs

• Total wood 22 x 56 = 1,232 tonnes, as printed. Investment 56 x Rs 25,000 = Rs 14 lakh, as printed.
• Rs 81,000 x 56 would be Rs 45.4 lakh, but the manual prints Rs 36.96 lakh. That is exactly 1,232 tonnes x Rs 3,000. Our reading: the unit figure fits Rs 3,600 a tonne, the cluster figure fits Rs 3,000, and the summary table's third figure, Rs 0.77 lakh a unit, fits 22 x Rs 3,500. The manual prints no wood price here.
• Cluster payback: 14 / 36.96 = 0.38 years, about 4.5 months. Using the manual's own cost table, which puts an improved chulha at Rs 0.56 lakh in total with civil work, 56 x 0.56 = Rs 31.4 lakh and the payback is about 10 months.
• The efficiency claim: the manual says 25 to 30% cuts the energy bill by more than 50%. At 25% the cut is 1 minus 15/25 = 40%; only at 30% is it 50%.

Put it to work

Weigh the wood per batch and the yarn bleached for a week before you build. If your chulha burns more than 0.75 kilograms of wood per kilogram, the saving is larger; if you already have a chimney and damper, it is smaller. The manual's wood is treated as non-renewable; report your own wood as tonnes bought and its carbon dioxide (CO2) as biogenic under the Greenhouse Gas Protocol's rule.

The unit and cluster sums, side by side

• Unit: 150 kg x 300 days = 45 tonnes; x 50% = 22.5 tonnes; x Rs 3,600 = Rs 81,000; 25,000 / 81,000 = 0.31 years = 3.7 months
• Cluster: 22 x 56 = 1,232 tonnes; x Rs 3,000 = Rs 36.96 lakh; 56 x 25,000 = Rs 14 lakh; 14 / 36.96 = 0.38 years = 4.5 months
• Cost table: 56 x Rs 0.56 lakh = Rs 31.36 lakh; 31.36 / 36.96 = 0.85 years = 10.2 months

Rs 3,600 is also the wood price in the manual's solar table. The reading that the unit and cluster lines use different prices is ours, from the arithmetic.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so wood bought each month is on file before and after a chulha change. Wood stays its own fuel line, and yarn bleached comes from your register.

• Efficient chulha: wood saving for dyeing
• Tiruppur solar hot water report checked
• Tiruppur dyeing unit firewood boiler emissions
• Tiruppur manual: payback table in months or years
• Green loan readiness check

Sources: BEE, Manual on Energy Conservation Measures in Textile Cluster, Tirupur (prepared by Winrock International India, via SAMEEEKSHA), GHG Protocol Corporate Accounting and Reporting Standard, Scope 1 definition

Last reviewed 2026-11-05. Figures are from the manual's study year (around 2010 to 2011). Wood prices and chulha costs have changed; check a current build quote.