How much electricity does a bulk milk cooler use per litre chilled, and what CO2 is that?

Work it out from the heat removed: litres x 1.03 kg per litre x 3.93 kJ per kg per degree x the temperature drop, divided by the COP and by 3,600 for kWh. Chilling 1,000 litres from 35 C to 4 C at a COP of 2.5 takes about 14 kWh, or about 9.9 kg CO2 on grid power.

The physics in three steps

1. Mass of milk = litres x 1.03 kg per litre.
2. Heat to remove (kJ) = mass x 3.93 kJ per kg per degree C x (milk in temperature minus target temperature).
3. Electricity (kWh) = heat / COP / 3,600, where COP is the cooling delivered per unit of electricity, from the maker's data at your ambient temperature.

Why the meter reads more than the formula

• Heat leaking into the tank through the walls and lid between collections.
• The agitator motor, which runs during chilling and at intervals after.
• Lower COP on hot afternoons, when the condenser struggles.
• Partly filled tanks: fixed losses spread over fewer litres.
• Fit a sub-meter on the cooler and divide monthly kWh by litres chilled. That measured figure beats the formula.

When power cuts bring in the DG set

Village chilling centres often run on a diesel generator during outages. Split the month's kWh into grid and DG. Grid kWh x 0.710 kg CO2. DG kWh / the generator's kWh per litre x 2.68 kg CO2 per litre of diesel. A small DG set at part load gives few kWh per litre, so DG hours can lift CO2 per litre sharply.

Where it sits in a dairy's footprint

If the cooperative or dairy owns and runs the cooler, its electricity is Scope 2 and its DG diesel is Scope 1. If a village society or a contractor runs it and charges you, it is Scope 3 for you. Refrigerant top-ups on the cooler add kg x GWP as CO2e.

Worked example: 1,000 litres a day, 25 percent of chilling on DG

• Mass: 1,000 x 1.03 = 1,030 kg
• Heat: 1,030 x 3.93 x (35 minus 4) = 1,25,485 kJ, so 34.86 kWh of cooling
• Electricity at an assumed COP of 2.5: 34.86 / 2.5 = 13.94 kWh
• Grid share: 13.94 x 0.75 = 10.46 kWh x 0.710 = 7.42 kg CO2
• DG share: 13.94 x 0.25 = 3.49 kWh / 3 kWh per litre (assumed) = 1.16 L x 2.68 = 3.11 kg CO2
• Total: 10.54 kg CO2 per 1,000 litres, about 10.5 g per litre

COP, DG efficiency and the DG share are assumptions; heat leaks and the agitator come on top. Replace with metered kWh and DG diesel.

What Senseible does here

Senseible reads electricity bills and diesel invoices and applies 0.710 kg CO2 per kWh and 2.68 kg CO2 per litre, so a chilling centre with its own bill and fuel invoices gets a monthly Scope 1 and 2 record you can divide by litres collected.

• Dairy plant emissions per litre of milk
• Diesel generator fuel consumption
• Ammonia or HFC for cold storage

Sources: CEA CO2 Baseline Database, version 21.0, 2006 IPCC Guidelines, Volume 2 Energy, Chapter 2, default CO2 factors and net calorific values

Last reviewed 2026-10-19.