Re: Does it really save that much?
According to my heating engineer the simple answer is no. He installed a new heating system for us with a new all-singing all-dancing programmable remote thermostat. It was his son that did all the electronic set up etc for us. He doesn't see the point. According to him the most efficient way to run a modern boiler is to use thermostatic valves on all the radiators. He reckons that, once the valve is set to the correct temperature on each rad. then the boiler will use absolutely bugger-all fuel maintaining the staus quo. Modern condensor boilers only really use energy when they have to change the temperature.
Although I should add that this really applies to modern, well insulated homes with decent windows etc. We'd just spent £2.5k on the boiler, cavity wall insulation, double insultating the loft and having any dodgy windows re-sealed which is why he thought we were wasting £120 on the gadget.