A cooling unit has one role: to maintain a consistent temperature inside a space as preset by a thermostat. The compressor unit that runs the fridge is therefore cycled on and off to maintain this ideal temperature.
This may seem logical, but the reality is that unnecessary amounts of energy are used to cool nothing but dead space. Think about it – what really matters – the air temperature inside the fridge or the temperature of the food itself?
The fact is that the two are quite different, as is the process of maintaining them. The thermodynamic properties of solid food vary massively from that of air, meaning that, whilst the air in a fridge may need to be cooled to reach the preset temperature, the food might well not.
Therefore, a significant chunk of the energy used by your fridge is wasted – attempting to keep food cool that is already at the desired temperature.