One correction to Cecil. Not all electric heaters are equally efficient. A heat pump can be 3-6 x more efficient than a simple electric heater as it dumps the “cold” outside
Cecil is talking about “space heaters”, portable heaters that can be placed anywhere usually to augment the central heating rather than replace it. Far different than a heat pump system.
While the OP is correct, Cecil’s column was not covering heat pumps within its scope, as Irishman says. Of course on “This Old House” the other day I did see a sort of heat pump space heater…but you can’t trust those guys ever since they booted out Bob Vila.
There are some electric heaters that are really very effecient. The oil filled electric space heater is very energy effecient. They use electricity to heat up and then after the oil is heated up you can turn it off. It continues to heat the room even after it has been switched off.
Cecil already addressed that here:
Yes, the oil is heating the room while the electrical source is off, but the energy in the oil had to come from somewhere. It came from the heater. It takes just as much (if not more) heat to heat the oil than it would take to heat the air for the same length of time. You’d either heat the air the same amount over the same length of time, or else make the air hotter for a shorter period of time.
Efficent is depending on the goal you want to achieve.
Heating your room or just a small area or do you need a barrier?
Quick heat - Clearly, it’s the Airheater with the coils and stuff, however, they generate only heat in a very small area and once turned of, the heat is usualy gone straight away.
Heating a room, the Oilfilled Radiotor are more efficent, it will take much longer for them to heat up, but once they are going, you can then turn them on low and they keep the room at that temperature more efficently.
Also the Oilfilled radiotors usually have a temperature gage in it, so it keeps coming on and off to heat the oil, meaning it uses less energy over a prolonged time, which is where you safe the buck.
In a drafty area (like a door in a shop) a fan assisted heater is much better, since it gets the air heated up rather quickly, but only in that area and can work as an Aircurtin.
In our cottage, we use a combination of airheater and Oil heater. We turn on both fully at the same time, then after 15 min we turn the Airheater off and keep the Oil radiator on low.
We figured it is the quickest and most efficent way to heat our little cottage.
That’s a thermostat. A gauge merely reports what the temperature is.
I get the feeling a couple of folks didn’t actually read the column, or barring that really are not getting what “efficiency” means.
I agree, Una.
How quickly the heat goes away has to do with how drafty the area is. An enclosed space with little air removal will retain air heat just as effectively whether the air was heated by an electrical coil, a ceramic heater, or a hot oil heater.
Air has a low thermal mass (i.e heat capacity). Oil has a high thermal mass. It takes a lot more energy to get the oil to the same temperature as the air. In order to heat the air, you first have to heat the oil. You can then turn the heating element off and let the heat dissipate more slowly from the oil, but that energy has already been spent on heating the oil. You aren’t saving any energy or money.
A fan assisted heater can move the air a bit more and thus keep the heat applied to a specific drafty area better. That is the fan directing the heat to where you want it. Not so much energy efficiency as effective directing of heat. Also not really addressing if the heater is radiative or convective.
As a child, we had an electric space heater that had coils like a toaster oven. It put out heat, but it was located right in front of the heater, and didn’t do much for the rest of the room. I currently own a ceramic heater. It has a ceramic heating element that I assume is radiative, but also has a fan. That heater can heat up a larger area, depending upon how enclosed vs. how drafty. It works very well at keeping my bathroom toasty for those pantless moments.