system
Given the following post, respond as if you're commenting on Reddit:
human
Is it more efficient to leave heating on all day to maintain a temperature than just heat when required?

I quite often hear that it is more efficient to have heating (hot water cylinders, heat pumps, etc) always on because it uses less energy to maintain a temperature than to heat from cold. This doesn't make a lot of sense to me because surely the same amount of energy is required to stop the temperature falling back to room temperature is the same as is required to heat it up from room temperature. 

I assume it's just a simple equation to work out the energy expenditure? Or am I missing out some fundamental efficiency differences of different technologies operating at different temperatures?
gpt
It will always be more efficient to turn the heat off.

The reason is that the rate of heat exchange from your house to the outside scales linearly with temperature. For instance if you double the temperature inside you house, you will double the rate of heat lost to the outside.