Considering all of the appliances that the average home uses--microwaves, light bulbs, dishwashers, refrigerators--is it safe to say that all of the electrical energy in a home will be converted to thermal energy inside the home?

If you think about the resistance going through wires, that is converted to heat. The photons from the light will eventually be converted to heat. The refrigerator makes excess heat. Is there anything that doesn't end up as thermal energy?

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    $\begingroup$ Some of it will become heat outside the home - any light that escapes through the windows, or sound that's audible from outside, for example. Or any batteries that you charge up and then use outside (phone etc.). But I imagine the proportion that escapes will be small. $\endgroup$ – Nathaniel Jun 5 '14 at 22:37
  • $\begingroup$ Good point, I didn't think about audible or battery use. This is more significant if one considers charging an electric car at home. But it is safe to say that everything else will eventually be converted to thermal energy correct? $\endgroup$ – Klik Jun 5 '14 at 22:47
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    $\begingroup$ Ah - of course the really significant one is air conditioning, which is specifically designed to cool the house and put heat outside. But I think if you're not using air conditioning, it's safe to say that the vast majority of power will become heat inside the home, at least for a time until it leaks out again. $\endgroup$ – Nathaniel Jun 6 '14 at 0:31
  • $\begingroup$ @Klik: In the end, it will all become thermal energy. So the real question is just about the percentage in the home. $\endgroup$ – MSalters Jun 6 '14 at 10:19

Ways I can think of to export energy from a home that do not heat the interior:
Light through windows
Radio energy from transmitters (WiFi, cell phone, radio, power supply noise)
Sound from stereo/TV
Charge in batteries
Hot items carried out (coffee in travel mug)
Pressure in car/bike tires supplied from your pump
Vented hot air from dryer, shower, oven, furnace, water heater
Hair heated by a dryer and still warm when you go outside

Many ways, but a very small proportion of the electrical energy entering

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    $\begingroup$ @rob: depending on how local you mean and how fast you drive with your coffee cup $\endgroup$ – Ross Millikan Jun 5 '14 at 23:14
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    $\begingroup$ Also, electrically heated hot water that runs down the drain... $\endgroup$ – DJohnM Jun 6 '14 at 0:38
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    $\begingroup$ Air conditioning! I think that's the only one that's likely to be really significant. $\endgroup$ – Nathaniel Jun 6 '14 at 0:39
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    $\begingroup$ @Hoytman - that would also be converted to heat within the home. $\endgroup$ – Mark Pattison Jun 6 '14 at 13:20
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    $\begingroup$ @Hoytman None of the appliances you mention displace anything permanently. $\endgroup$ – Rawling Jun 6 '14 at 13:46

My electric heat-pump removes more sensible heat from my house than it adds into it - and the electric bill comes to the house. So perhaps the answer should be no.

The point is the temperature of my house, may not be proportional to how much electricity we use that day.

  • $\begingroup$ "The point is the temperature of my house, may not be proportional to how much electricity we use that day." That's an excellent point. Can you elaborate on where the energy goes if it does not end up as thermal energy? $\endgroup$ – Klik Jun 6 '14 at 7:47
  • $\begingroup$ @Klik: It goes outside. Usually mostly into the air, although some setups might also transfer heat into the ground. $\endgroup$ – Ilmari Karonen Jun 6 '14 at 10:06

How about this also: you use electricity at home for heating, cooking etc to maintain the life of people and pets in the house. Then they go outside and perform mechanical work on something, e.g., at the gym.

For example, consider the reaction of ethanol burning (without worrying about details)

$C_2H_5OH + O_2 = CO_2 + H_2O$ + energy

Now imagine somebody cooking moonshine alcohol at home, combining [electrical] energy, water, and carbon dioxide. In principle this should be possible, the reaction is reversible. Next this individual consumes the product and goes outside to work out, or do some other great things involving some mechanical work. This would be the case of using electricity at home that does not end up as heat at home.

More seriously, we could consider other chemical reactions that can be carried out at home using electrical energy, that would produce some "fuel" for a human being (or his pet, his car, his toy helicopter etc) that would be able to use it for doing mechanical work outside of the house.

  • $\begingroup$ -1. The observations may be correct but this answer is about sociology, not physics. $\endgroup$ – MSalters Jun 6 '14 at 10:18
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    $\begingroup$ Mechanical work done by humans or animals is fueled by the food energy they consume, not by electricity. The energy used to heat food for cooking does not incorporate as food energy in the cooked food. $\endgroup$ – J... Jun 6 '14 at 10:57
  • $\begingroup$ @J... - maybe not, but it heats up the body and causes the person to expend less calories keeping itself warm. $\endgroup$ – Mark Pattison Jun 6 '14 at 13:22
  • $\begingroup$ @MarkPattison Doesn't matter. The question is about electrical energy that does not end up as heat in the home, and you're talking about direct electrical-to-heat conversion in the home (ovens and heaters), so obviously it doesn't apply. The subsequent use of that heat to support other energy cycles (food / work) is irrelevant. The only way this applies to the question is in considering that some of the added heat stored at the person's body will not be in the home when the person leaves, but this has nothing to do with the work performed by the person. $\endgroup$ – nmclean Jun 6 '14 at 13:53
  • $\begingroup$ @MarkPattison It does not. Unless you keep your home dangerously warm inside, it is the human that is adding heat to the house and not the other way around. The human is the hot object and the room is the cool object - heat flows from the human to the room. $\endgroup$ – J... Jun 6 '14 at 17:32

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