Everyone always talks about the efficiency of their appliances. I was wondering if everything was 100% efficient at heating its surroundings ?
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An electric heater that has "mechanical inefficiencies" as Programmer mentioned will nonetheless ultimately lead to near 100% conversion because things like expansion of wires, creaking sounds etc., will be absorbed by the surroundings and turned into heat, especially in a well-insulated house.
I justify leaving the bathroom CFL light on in the winter (it takes a few minutes to brighten up) because we would just run the heater anyway, and the heat that it emits just offsets electric heating. Similarly for devices wear through on/off cycles.
Appliances can be more than 100% efficient, e.g. heat pumps.
answered Dec 3, 2013 at 0:39
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$\begingroup$ Ironically in some areas with hydro-electricity but gas heating the introduction of CFLs can significantly increase emissions in winter. $\endgroup$ Commented Dec 3, 2013 at 4:17
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$\begingroup$ @MartinBeckett the evidence I've seen says otherwise. Do you have any empirical data? $\endgroup$– 410 goneCommented Dec 3, 2013 at 7:42
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$\begingroup$ There was a report (admittedly from U Alberta) which showed IIRC a tiny increase for BC and Quebec. Essentially places with almost 100% hydro electric but natural gas heating and little summer AC. They also had a small local increase in Mercury because they don't have much coal fired capacity to reduce. Across the country and most of the world though CFLs are a "good thing" $\endgroup$ Commented Dec 3, 2013 at 16:34
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Transfer of heat from one source to another can be very efficient. In fact, the first law of thermodynamics says that the internal energy of a system can be transferred as heat of there is no work done through compression, expansion etc. For example, electric heaters can deliver close 99% of the heat energy to their surrounding with minimal loss from mechanical effects such as expansion of the wires.
Everyone always talks about the efficiency of their appliances.
No. You don't hear everyone talk about the efficiency of heating because efficiency is related to the work output or energy conversion. People talk about efficiency of a water heater for example, to say how much of the chemical energy in the fuel is converted to heat energy. Or an electric heater to refer to how much of the electrical energy is converted to heat.
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1$\begingroup$ People do talk about the efficiency of heaters. Sometimes this is misguided, but sometimes not. E.g. If it's a gas boiler it might let substantial amounts of heat out of its exhaust. Or it might be a heat pump used to transport heat in from the outside, which can be more efficient than simply converting electricity into heat. On a more informal level, if all the heat ends up in a layer of hot air near the ceiling, this can also be considered inefficient. $\endgroup$– N. VirgoCommented Dec 3, 2013 at 4:48