# Does the Surat manual's heat recovery on 300 units save 50,000 tonnes of coal or 87,600?

Canonical: https://senseible.earth/answers/surat-300-drain-heat-exchangers-50000-or-87600-tonnes

The Bureau of Energy Efficiency (BEE) Surat manual prices a jet machine drain heat exchanger at 292 tonnes of coal and rupees (Rs) 10.22 lakh a year for each unit. For about 300 units it prints 50,000 tonnes and Rs 1,750 lakh; 300 times 292 is 87,600. The unit's 292 is 886 kilograms times 330 days, not 350.

## One unit, as printed

- Hot water drained: 85,000 litres a day, 68,000 taken as the conservative 80%. Temperature 90 degrees Celsius. Heat recoverable 27,20,000 kilocalories (kcal) a day. Operating days 350.
- Boiler efficiency 51%, coal at 5,800 kcal a kilogram (kg), fuel saved 886 kg a day, 292 tonnes a year at Rs 3,500 a tonne: Rs 10.22 lakh (1 lakh = 100,000). Investment Rs 6.00 lakh. Payback printed as 6 months.

## The cluster line against it

The text says the scheme can be implemented in about 300 units, saving 50,000 tons of coal and Rs 1,750.00 lakh a year, for Rs 1,800.00 lakh, with payback around one year.

Investment rebuilds: 300 x 6.00 = 1,800. Savings do not. 300 x 292 = 87,600 tonnes, not 50,000; 300 x 10.22 = Rs 3,066 lakh, not 1,750. The printed 50,000 and 1,750 both fit 171 units (50,000 / 292 and 1,750 / 10.22). So the cluster saving looks like 171 units' worth and the cost like 300 units'. The manual does not say why.

Which way it runs: at 300 units and 292 tonnes, the cluster payback is 1,800 / 3,066 = 0.59 years, about 7 months, which matches the single unit. The printed 'around one year' is the cautious one.

## Small differences inside the unit table

- 886 kg x 350 days = 310 tonnes. 292 tonnes is 886 x 330 days, so the days line and the tonnes line do not use the same year.
- At 51% and 5,800 kcal the heat gives 27,20,000 / 0.51 / 5,800 = 920 kg a day, not 886. At 6,000 kcal it is 889.
- Payback 6.00 / 10.22 = 0.59 years, 7.0 months, printed as 6.

## What to take from it

Use your own drain volume and temperature, your own days, and your invoice price. Do not multiply the per-unit saving by a cluster count and quote the product as a result: it is a potential, not a measured saving.

## The two cluster totals side by side

- Printed: 50,000 tonnes, Rs 1,750 lakh, Rs 1,800 lakh invested
- Units implied by savings: 50,000 / 292 = 171; 1,750 / 10.22 = 171
- Units implied by cost: 1,800 / 6.00 = 300
- At 300 units: 300 x 292 = 87,600 tonnes; 300 x 10.22 = Rs 3,066 lakh; payback 1,800 / 3,066 = 0.59 years

Inputs are the manual's, at its year's prices. The reading of 171 and 300 is our arithmetic.

## What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so the coal bought each month is on file, ready to test a saving against your own tonnes. It does not measure drain water or heat; that needs a flow and temperature log.

- [Surat drain heat recovery reports](https://senseible.earth/answers/surat-drain-heat-recovery-reports-compared)
- [Surat coal heating value in the manual](https://senseible.earth/answers/surat-manual-coal-heating-value-4100-4500-5800-or-6000)
- [Green loan readiness check](https://senseible.earth/green-loan-check)

Sources: [BEE, Manual on Energy Conservation Measures in Textile Cluster, Surat (SAMEEEKSHA)](https://sameeeksha.org/pdf/clusterprofile/Surat_textile_cluster.pdf)

Last reviewed 2026-11-06. Figures are the manual's, at its year's prices. Measure your own drain volume and temperature before sizing.