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What does consumption ratio and non-consumption ratio mean
In the electric radiator market there is a lot of jargon being used. One particular brand likes to talk about consumption ratios and non-consumption ratios, so what does this mean?
Usually expressed in percentages, it refers to the amout of time in the hour that the heater is using electric power from the mains.
What will decide how long the radiator is on each hour?
This will be determined by the nominal power of the heater and the heat loss of the room. It is also affected in a very small percentage by the accuracy of the thermostat control on the heater.
The heat loss of the room is determined by the U values ( insulation values ) of all the materials used in the building i.e the windows, walls, roof, doors etc. A new build property will have very low heat loss while an old property will likely have quite high heat loss. The heat loss also depends on the temperature difference between the internal air and the external air. The warmer it is inside and the colder it is outside the greater the heat loss will be.
Without knowing the U values of your building it is not possible to know the heat loss or the consumption ratio.
For easy calculation, let’s assume the room has a 500watts per hour heat loss.
If we have a 2000 watts radiator in this room with a good thermostat it will produce just 500 watts of heat each hour to counteract the room heat loss and maintain a steady state ambient temperature. In order to do this, the radiator would be on for 25% of the hour because 500 watts is 25% of 2000 watts. In this case the consumption ratio would be 25% and the non-consumption ratio would be 75%.
Now if we put the same 2000 watts radiator in a room in an older building with higher heat loss, lets say 750 watts per hour heat loss then it would need to produce 750 watts of heat each hour. It will therefore be on for 37.5% of the time and off for 62.5% of the time. This would be 37.5% consumption ratio and 62.5% non-consumption ratio.
All electric radiators have exactly the same efficiency of heat production. 100% of the electricity used is converted to heat, this is called joule’s law.
Every electric radiator from every brand will have exactly the same consumption ratio and non-consumption ratio when used in the same specific environment.
It is not possible to state consumption ratio or non-consumption ratio for a radiator, because it depends entirely on the environment that it is being used in. Any percentages quoted by manufacturers are based on laboratory tets in a specific environment with a controlled heat loss. This will have no bearing on the consumption in real life as each house is different. The consumption ratio will also change each day as the outside temperatures change.