Heat your house by an extra degree and your bill goes up by 8%…
So, do you really need or want every room in the house to be at the same temperature all the time. Do you need to heat the spare bedroom when nobody is in there, and do you want your bedroom as warn as the baby’s room? A gaggle of teenagers will warm up a bedroom pretty efficiently, so you don’t need the radiator in there blasting out heat as well, so fit a radiator thermostat, which will monitor the room temperature and adjust the flow through the radiator.
The whole house thermostat doesn’t offer any precision and cannot react to changes in other parts of the house, such as sunshine streaming into a south facing room, or, indeed, the back door being left open, losing all the heat from the kitchen…