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

Canonical: https://senseible.earth/answers/bulk-milk-cooler-electricity-per-litre

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](https://senseible.earth/answers/dairy-plant-emissions-per-litre-of-milk)
- [Diesel generator fuel consumption](https://senseible.earth/answers/diesel-generator-specific-fuel-consumption)
- [Ammonia or HFC for cold storage](https://senseible.earth/answers/ammonia-vs-hfc-cold-storage-refrigerant)

Sources: [CEA CO2 Baseline Database, version 21.0](https://cea.nic.in/cdm-co2-baseline-database/?lang=en), [2006 IPCC Guidelines, Volume 2 Energy, Chapter 2, default CO2 factors and net calorific values](https://www.ipcc-nggip.iges.or.jp/public/2006gl/vol2.html)

Last reviewed 2026-10-19.