I made a mistake with last house, I read the specification and found a Horstmann wireless programmable thermostat that seemed very good, think it had 5 times a day and each day of week could be independent, however it did not have a fail safe, so a set of flat batteries could result in heating not turning off, however as you go to the more expensive types that will switch off with a battery failure they tend not to be programmable until you get to the internet connected type.
So looking and Tado, Evohome, Hive and Nest. With some of the units it is a pain getting a supply to thermostat, may be wireless but still needs USB or other form of power, with the combi boiler the new Nest E seems to have all that is needed, and is battery powered, however it all depends how far you want to go with control? I think the Evohome looks really good where the thermostat (hub) takes the temperature from the TRV heads in each room, where Nest does work with Energenie the latter TRV heads can follow Nest plus have extras programmed in, but not as well integrated as EvoHome. However using OpenTherm some thermostats even report the temperature of the DHW.
Until I fitted Nest I did not realise what it can do, in fact it caught me out, as it was doing things which seemed random until I read instructions more carefully.
However much depends on how much money your wanting to spend, I have ordered some TRV heads which are bluetooth for just £15 each, they will not link to Nest or any other wall thermostat, but will allow me to set room temperature in degs C and to program when the room is heated. Clearly any programmable TRV head unless connected to the wall thermostat will not turn boiler on at a temperature change, so when they move from 16°C over night to 20°C in the day nothing will happen until boiler runs.
We are told the wall thermostat should be in a room on ground floor, with no outside doors, or alternative form of heating, I simply don't have such a room, so central heating is a compromise, I have expensive Energenie TRV heads in the hall and adjoining rooms which link to Nest, so any change is done on all 5 units, but using cheaper bluetooth upstairs, as to how well it will work, I can only guess.
This house oil simple off/on, last house gas combi modulating, it took me 2 years to get the setting right, adjusting lock shield valves and matching TRV heads with wall thermostat, the latter was really too clever, it was in the hall and all I wanted was for it to turn off/on summer/winter, however it had anti-hysteresis software which resulted in as it approached set temperature it started to cycle off/on so it did not over shoot, however every time a boiler turns off, energy is lost out of the flue, so with a modulating boiler you want boiler to modulate first, before it turns off, with this house boiler does not really modulate so the anti hysteresis software is good.
When the combi modulating boiler first came out, the idea was not to have wall thermostats, the TRV would do all the temperature control, and the boiler modulated by reading the return temperature of the water, then we started to get electronic heads on the TRV and wall thermostats which modulated the boiler, and we also got a lot of miss match of controls, today it's a nightmare, with loads being miss sold, yes with one house with one boiler the new fanged thermostat can work very well. But not with all houses or all boilers.
So we are left scratching our heads, wondering is it worth it? I at last house tried geofencing, but the anti-hysteresis software in the TRV heads increases time taken to reach a new temperature, so to get room at new temperature on arrival home, it needed to turn to new temperature 2 hours earlier, how many people work two hours from home? So all the cleaver systems may work, but likely no use for most people.
And if you spend £500 on control, will it pay for its self? To be fair I had one house with hot air heating, from cold house, and I mean 6°C to warm 20°C it took ½ hour, and because air circulated around all rooms, they all were at same temperature, so in 1976 had I been able to turn on heating remotely it would have worked well, however blowing air past single glazed windows resulted in huge loses, so expensive to run, and it did not heat domestic water. Next house had a Myson fan assisted radiator and again really fast heating the room, also room soon cooled when it switched off, as fan assisted radiators don't store heat.
But I am sure with the modern variable speed fan assisted radiator the home could be heated quickly and efficiently, the ivector Myson looks really good, and they are a really good price, so maybe a plinth type in kitchen, but too expensive for rest of house.
