How much boiler fuel does a 5,000 LPD solar water heater save in a dairy?

About 31.5 kg of furnace oil a day in BEE's Gujarat dairy report: 5,000 litres heated by sun from 27 C to 70 C for CIP and makeup water saves 9,450 kg of FO a year, about 31 t CO2 and 15% of the chilling centre's oil. Cost Rs 6.54 lakh, saving Rs 2.84 lakh, payback 2.3 years.

The chilling centre in the report

• Receives about 150,000 litres of raw milk a day, chills it, cleans cans and tankers and sends the milk on to the main dairy.
• Uses 974,664 kWh of power a year, mostly for chilling.
• Burns about 175 kg of furnace oil a day, 63,036 kg a year, in a hot water generator at about 65% efficiency, mostly for cleaning in place (CIP).

What the solar system does

Flat plate collectors heat 5,000 litres a day to about 70 C and store it in an insulated tank. That water feeds CIP and preheats makeup water, so the oil-fired generator only tops up to the 70 to 85 C that CIP needs. The report counts 300 effective sunny days a year and a week of downtime to connect it.

The saving, step by step

1. Heat: 5,000 litres x (70 minus 27 C) = 215,000 kcal a day.
2. Oil: 215,000 / (65% x 10,500 kcal a kg) = 31.5 kg a day.
3. Year: 31.5 x 300 days = 9,450 kg, worth Rs 2.84 lakh at Rs 30 a kg.
4. Cost: collectors and tank Rs 5.46 lakh, design Rs 0.25 lakh, erection Rs 0.75 lakh, civil and contingency Rs 0.08 lakh: Rs 6.54 lakh. Payback 6.54 / 2.84 = 2.3 years.
5. The report's cost table prints civil work as Rs 0.10 lakh, which would make Rs 6.63 lakh; its annexure uses Rs 0.01 lakh, which gives the Rs 6.54 lakh total.

Before you size one

• Measure how many litres of hot water CIP and washing really take each day. A tank bigger than the demand saves nothing more.
• Monsoon weeks give far less heat; the 300 day figure already allows for that.
• Plan roof space and the tank's weight, and keep collectors clean of dust.

One chilling centre, one year

• FO saved: 9,450 kg / 0.9 kg a litre = 10,500 litres
• CO2: 10,500 x 2.97 = 31.2 t
• Share of the centre's oil: 9,450 / 63,036 = 15% a year, 18% on a sunny day
• The report's 32 t is close

Furnace oil at 2.97 kg CO2 per litre, using the report's specific gravity of 0.9.

What Senseible does here

Senseible reads furnace oil invoices and electricity bills into monthly records with CO2, so the oil bought before and after the solar system is on record bill by bill. For solar thermal finance, start with the green loan check.

• Green loan readiness check
• Solar water heater CO2 savings
• Gujarat dairy chilling centres: energy
• Dairy refrigeration desuperheater

Sources: BEE, Detailed project report: solar water heating system 5,000 LPD, Gujarat dairy cluster (SAMEEEKSHA)

Last reviewed 2026-11-01. Report figures are from a BEE SME programme project report; costs and paybacks are at the report year's prices. Check today's furnace oil price and a current quote.