There is three ways to move heat energy, conduction, convection, and radiation. The conduction would only work with an electric blanket, so left with convection and radiation, the radiation uses electromagnetic waves in the infrared spectrum which can pass through some glass, and air without heating it, and heats the body direct, however it is instant, so as soon as turned off it stops, so one can't use a mark/space ratio to control it, only way was with say a 4 bar heater having one to four bars switched on, and the thermostat will not really work with it.
However for years we did use it, until the government stopped us, what we did was heat the air to say 18°C and use the infrared so it felt like 20°C switching it on only when using the room in the dark. We called this clever system tungsten lights.
When I moved from tungsten to compact fluorescent I also had to fit a programmable wall thermostat so the day and evening temperatures changed at the same times as when I would have switched on the lights.
So in the winter the tungsten bulb saves energy, but since we normally heat with gas or oil, not money. However with infrared heating it is important to close curtains, as it can pass through older glass. Today glass is coated to stop infrared passing, but it needs to be the right way around.
There is a
BBC review on the small plug in fan heaters, the
pod cast is here they point out like infrared as soon as it switches off, you feel cold, so one tends to keep switching it up.
The review seems to be down to control, what one wants is just enough to keep you warm, then you want a heater which gives out a continuous heat, if the heat output switches on/off you will feel cold every time it switches off.
So the water or oil filled radiator may have the heating input switches on/off, but the heat output is continuous, it acts as a buffer storing the heat when on so it is still giving off heat when off.
It seems not down so much to heat given into the room, but that the heating is constant. So a smaller fan heater will switch off less, so likely will make you feel warmer for longer than a large fan heater, but the oil filled radiator it seems is best for making one feel warm.
