Why do the Bureau of Energy Efficiency (BEE) Solapur reports pay back a new 200, 400 or 600 kilogram an hour wood boiler in 3.7, 2.8 and 1.1 years?

BEE's Solapur reports price a new wood fired hot water boiler at rupees (Rs) 2.97 lakh for 200 kilograms (kg) of steam an hour, Rs 3.22 lakh for 400 and Rs 5.91 lakh for 600. They save 32, 38 and 207 tonnes of wood a year, with printed paybacks of 3.7, 2.82 and 1.14 years.

The three reports side by side

• 200 kg: the old boiler runs at 32.6% and burns 72 tonnes a year. The new one is 65% efficient and burns 40. Saving 32 tonnes x Rs 2,500 = Rs 0.80 lakh. Cost Rs 2.97 lakh. Payback 3.7 years, internal rate of return (IRR) 14.26%, net present value (NPV) Rs 0.34 lakh.
• 400 kg: old boiler 32.9%, 72 tonnes a year. New one 70% efficient in its specification table (65% in its annexure), 34 tonnes. Saving 38 tonnes. Printed benefit Rs 1.14 lakh, cost Rs 3.22 lakh, payback 2.82 years, IRR 14.26%, NPV Rs 0.37 lakh.
• 600 kg: old boiler 39.56%, 480 tonnes a year. New one 65% efficient, 273 tonnes. Saving 207 tonnes x Rs 2,500 = Rs 5.18 lakh. Cost Rs 5.91 lakh. Payback 1.14 years, IRR 57.08%, NPV Rs 9.55 lakh.
• The 200 and 400 kg reports start from the same 72 tonnes. So the 400 kg boiler saves more only because its printed fuel line is lower (34 tonnes against 40), not because it serves a bigger unit. The 600 kg report starts from a unit using more than six times as much wood.
• Each says the unit works 240 days. Hours are 8, 6 and 8. Each says its efficiency gain is over 15%, which qualifies for a subsidy of 25% of project cost under the National Manufacturing Competitiveness Programme scheme of the Ministry of Micro, Small and Medium Enterprises, and that the subsidy is not taken off the project cost: Rs 0.75, 0.80 and 1.48 lakh.

Where the printed figures do not tie

• The 400 kg report prices wood two ways. Table 3.1 uses Rs 2,500 a tonne and saves 38 tonnes, which is Rs 0.95 lakh, not the printed Rs 1.14 lakh. Its annexure comparison table and financial sheet use Rs 3,000 a tonne, and 38 x Rs 3,000 is Rs 1.14 lakh. So the Rs 1.14 lakh and 2.82 years follow the annexure price; this is a price conflict inside the report, not an arithmetic slip. Read on the Table 3.1 price, the payback is 3.22 / 0.95 = 3.4 years.
• The 200 kg text says in one place that the annual monetary saving is Rs 2.97 lakh; that is the project cost. The table and summary say Rs 0.80 lakh. Its carbon text says 30 tonnes of wood saved, the table says 32.
• The 200 kg summary table says 3 days of downtime, its text says 6 to 7 days.
• The 200 kg annexure says the new boiler burns 42 tonnes and saves 30; its text and Table 3.1 say 40 and 32.
• The boiler specification sheets print rated wood use of 27, 95 and 34.2 kg an hour for 200, 400 and 600 kg boilers. A 600 kg boiler burning less than a 400 kg one is not plausible, so do not read the three as a size scale.

Do the savings follow from the efficiencies?

Our check: old tonnes x old efficiency / new efficiency gives the new fuel. 200 kg: 72 x 32.6 / 65 = 36.1 tonnes, so a saving of 35.9, more than the printed 32. 400 kg: 72 x 32.9 / 70 = 33.8, matching the printed 34, but only on 70%. The report gives both 70 (specification table) and 65 (annexure comparison table); at 65% the figure is 72 x 32.9 / 65 = 36.4 tonnes, which does not match. 600 kg: 480 x 39.56 / 65 = 292.1, a saving of 187.9 against the printed 207. The printed 273 tonnes needs about 70% efficiency, not the 65 plus or minus 2% in its own specification.

At 65%, the 600 kg saving would be 188 tonnes, Rs 4.70 lakh, and payback 5.91 / 4.70 = 1.26 years. Still good, a little less.

The carbon dioxide (CO2) lines

Each report counts wood saved at 1.4 tonnes of CO2 a tonne: 45, 53 and 290 tonnes a year (32 x 1.4 = 44.8; 38 x 1.4 = 53.2; 207 x 1.4 = 289.8). Our reading, as on the linked pages: CO2 from burning wood is biogenic and is reported apart from Scope 1, so these are not Scope 1 cuts. What a wood fire leaves in Scope 1 is its methane and nitrous oxide, which are small.

Before you buy

• Weigh your own wood for a month and note hours fired. Both drive the saving more than the boiler's size.
• Check the wood price. The reports use Rs 2,500 a tonne at 2010 prices, and Rs 3,000 in places in the 400 kg report.
• Ask the maker to guarantee efficiency at your part load, not the design point.

The 600 kg report, rebuilt

• Wood: 480 less 273 = 207 tonnes x Rs 2,500 = Rs 5.175 lakh, printed Rs 5.18 lakh
• Payback: Rs 5.91 lakh / Rs 5.18 lakh = 1.14 years
• At 65% efficiency, our check: 480 x 39.56 / 65 = 292.1 tonnes; saving 187.9 tonnes = Rs 4.70 lakh; payback 1.26 years
• Printed CO2: 207 x 1.4 = 289.8 tonnes, biogenic, not a Scope 1 cut

Printed lines are the reports' own at the reports' prices. The efficiency check is our arithmetic.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so wood or briquette purchases by month are on file to test a report's baseline against. It has no wood factor, so keep wood tonnes beside the figure.

• Towel and bed sheet unit: wood and power per kg
• Solapur textile cluster wood fuel carbon
• Efficient chulha in dyeing: wood saved
• Green loan readiness check

Sources: BEE, Detailed project report: energy efficient boiler (200 kg an hour), Solapur textile cluster (SAMEEEKSHA), BEE, Detailed project report: energy efficient boiler (400 kg an hour), Solapur textile cluster (SAMEEEKSHA), BEE, Detailed project report: energy efficient boiler (600 kg), Solapur textile cluster (SAMEEEKSHA)

Last reviewed 2026-11-05. Report figures are from BEE's Small and Medium Enterprises (SME) programme project reports, with wood at Rs 2,500 a tonne, and Rs 3,000 in the 400 kg report. Check today's wood price, your measured boiler efficiency and a current quote before you rely on the payback.