There are three basic ways of heating with electric.
1) The heat pump, expensive to install, and when using the air rather than ground they can freeze up, but can also cool in summer.
2) Radiant heaters, used where there are a lot of air changes, it heats the items in front of it rather than the air, the heat is not stopped by windows so needs to be aimed correctly, very hard to control, heat is instant, but also it is removed in an instant, so can't really switch on and off to control heat, one has to have them in sections so you have more or less bars on with the fire. So not automatic controlled.
3) The converter heater, now these do come in different efficiency ratings, but not as one would expect I will try to explain.
If we look at the worst converter heater this would be under floor heating, these need to be turned on over an hour and a half before you want to use the room, they will continue to warm the room after being turned off, but if we consider the room is used for 5 hours then you use the heater for at least 6.5 hours so it is 5/6.5 x 100 = 77% efficient. Go for the fan heater with is likely the more efficient other than 1) and 2) above then it will likely heat the room in 20 minutes so around 94% efficient. But in both cases using the heater 24/7 they both become 100% efficient so it is down to how long the room is wanted for.
As with the radiant heater switching off the fan heater very quickly the room becomes cold, so with a fan heater the mark/space time (the time the heater is on and off) has to be short so likely turning on and off every 5 minutes with thermostatic control, with the oil filled radiator (or under floor heating) then the heat is still released when the power has been turned off by the thermostat, so these could well have 1/2 an hour between each cycle, and not make the user perceive that the room has cooled. So although the fan heater in theroy costs less to run, the oil filled radiator is more comfortable as you don't feel cold before it switches on again.
One would think the best place for a thermostat is away from the heat source so that it monitors the room temperature rather than the heating device temperature, however this does not work, as the mark/space time becomes too long, so you feel cold before it turns on again. So having the thermostat built into the heater actually works well, however you have to compensate for the temperature drop as you move away from the heat source. So with hot water heating systems we have thermostatic radiator valves (TRV) which are fitted on the radiator, but instead of being marked 10 ~ 35°C they are simply marked 1 ~ 6 and the user adjusts to a comfortable temperature.
So you want the thermostat built into the heater, and the heavier the heater (the greater its mass) the less efficient, but also with the exception of off peak heaters the more comfortable heating they produce. So in real terms the only way to save money is the timer, switching the heating off when not required, and of course on so the room is warm when it is required.
There is to be fair one other way to reduce energy used, and that is to adjust temperatures to suit the time of day, so the bedroom for example, heat turns on at 9:30 to get the room warm to retire in at 10:00, but at 10:30 it switches to 15°C instead of 20°C until 6:30 in morning when it goes back to 20°C ready for you waking up, then at 8:00 it switches off again.
Unless the system can monitor outside temperature then it does not know how long it needs to warm up the house, so having a timed thermostat which has house at 15°C then raises it to 20°C in the evening means there is a fixed heating time. However most the programmable thermostats are designed for hot water systems and so have contacts unable to take the load of direct electric heating.
The complex systems like the Honeywell Evohome and the more simple systems like hive and nest are all designed for a system with one central heating device with Evohome for a hot water system, with hive and nest a hot air system, although people do try using hive and nest with water systems. The whole point with hive and nest is that you can adjust the heating with your mobile phone. It would need a relay box because the contacts can't take the current of direct heating, but there is no reason why they should not be used with direct electric heating.
Of course there is also no reason why any form or SCADA control should not be used with a remote computer adjusting the settings. Electrical engineers often access complex machines at work from the comfort of home using an internet connection and diagnose faults and make adjustments. So there is in theroy nothing to stop the reverse, and having a PLC with SCADA control your home heating so at work you can bring up a plan of the house and adjust the heat in every room. Where it falls down is if it goes wrong you would need expertise not normally found with domestic heating engineers or electricians.
We have seen on these pages where some one had a system common in USA but not in UK and could not find anyone to work on it. KISS is often quoted, keep it simple silly, and yes simple plug in time clocks are likely the best system together with built in thermostats on the heaters. Using oil filled radiators in the bed room once they switch off they cool down slowly so you will likely sleep through the night without getting cold even after they have turned off, and they are unlikely to set anything on fire.
Convector heaters do work well, but you must ensure no paper etc can fall on them as hot spots could cause fires, so not suitable for a room used as an office. The lighter the heater the more economic it is in general, but the less cosy. You have to select, but with type 3) they are all 100% when used 24/7 the ratings quoted showing some are better than others is all about how quickly they heat the room so how long they have to be on before the room is used. So don't get conned into thinking some are really better than others.
