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Does it make sense to keep electrical appliances turned on, or at least not turned off, during the winter as a partial replacement for traditional heating?

I'm thinking in particular of computers, screens, audio and video equipment and home entertainment systems.

Seems to me there is no difference between heat from electrical resistance in a wasteful gadget and heat from the same process in a regular space heating system. And if the heating system is fossil-powered, there is presumably a chance that replacing some of it by "energy inefficiency" would end up a greener solution.

Is this reasonable, and if so what factors could determine the calculation?

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Generally, it makes sense to save power, even during the winter.

The difference between space heating and waste heat

The main difference between home heating systems and waste heat from electrical appliances is the way the heat is released, and where it's released. Many types of home heating systems are designed to provide heat in a specific way, such as a fan heater pointing in the general direction of someone feeling cold, a radiant heater pointing towards a family while they watch TV, or a fireplace in the living area.

Heating that is well targeted at the recipients uses less energy than heating that just increases the ambient temperature of the building. This is very much the case in a poorly insulated building where there's not really much point trying to heat the whole building; the heat is lost very quickly anyway.

Insulation, and the type of heating system, makes a big difference

In a well insulated building that runs thermostat-controlled space heating, waste heat from appliances would tend to reduce the load on the space heating system. In that case, one needs to also consider the type of space heating system; if it's efficient or environmentally friendly (like a heat pump, or a system using clean burning renewable fuel), then it's almost certainly better to use the heating system rather than appliances. It is possible though that electricity may be more renewable than the space heating, in which case more detail would be needed.

Other factors

Also bear in mind that appliances don't last forever. Depending on the appliance, and the profile of its use, the life of the appliance may be longer if switched off each time or if left on.

A good general rule would be to switch off anything not being used that consumes more a negligible amount of power (such as lighting, televisions or computers), but it's not so bad to leave on standby appliances that only use a Watt or two. You can use a power meter to work out which ones don't matter so much. You'd probably find some tvs, computers, stereos etc use lots of power on standby and others use very little, so it's worth checking.

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    Using my electricity bill as the average price for my usage (I have a day/night pay regime) I calculated that 1W powered on for a whole year costs me €1.3. I use that as the measuring stick to see if I should leave a device on or even replace it in case it needs to be on for long times. – w00t Dec 24 '14 at 10:06
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Heating with electricity is wasteful because it implies the heat that could not be converted to electricity at the point of generation. It's roughly 50-70% for fuel-powered plants and 70-80% for photovoltaics (but not really an issue there, as sun and space are usually abundant). That implied waste heat could heat many homes for free, if only we'd have a way to deliver it long-distance …).

However, if you run your electrical appliance to do meaningful work that has to be done anyway, and then utilize its waste heat for room heating, it is a greener solution since you save heating fuel.

A computer is quite useful in this scenario, since there are quite some meaningful tasks for them to do while contributing to heating your home:

  • Personal server housing. If you have enough Internet bandwidth, you can put a web server for yourself, your company or a friend into your home.
  • Cloud computing / hosting. German startup Cloud&Heat wants to do something against the enormous amounts of heat wasted when cooling centralized data centers. They offer to place a rack with cloud servers into your house and pay the electricity and bandwidth for it. So you get the servers' waste heat for free and can use it for water heating (connections provided) or space heating (via the heated water and a buffer tank).
  • Distributed computing. The best-known distributed computing infrastructure is BOINC. In the BOINC Manager application at "Tools → Add Project…" you are presented with the official BOINC projects, all for advancing science. However, you can also contribute to any of the third-party BOINC projects by typing in the project URL. (Example: http://burp.renderfarming.net/ for contributing to BURP distributed 3D rendering.) None of these projects pay your increasing electricity usage, but at least you can opt to support science :)
  • "Useful" cryptocurrency mining. Some new cryptocurrencies allow mining with meaningful scientific calculations rather than just calculating millions of hash checksums as in the case of Bitcoin. The amount of cryptocurrencies you earn this way is not sufficient to cover the electricity bill, but again, you can support science.
  • Normal cryptocurrency mining. If you consider this "meaningful work", it's an option as well. It can pay off in monetary terms ("you get the heat for free"), but resource-wise mining Bitcoins and other proof-of-work cryptocurrencies is an intentional waste of energy. Also with Bitcoin, you will need energy-efficient ASIC hardware (not cheap…) in order to break even. Having your energy costs covered is always the "market equilibrium" in Bitcoin mining, so in principle you can get the heat for (nearly) free, but it's not easy to achieve and the required investments are speculative risks.
  • mining cryptocurrency is almost the perfect example of an entirely wasteful activity. By definition, it is participating in a contest to see who can waste the most resources, and the output is the checksum of a spreadsheet, which by itself is not useful (but is much cheaper to compute than the mining process). – Ⴖuі Sep 10 '16 at 22:51
  • @Ⴖuі That's right. Money-wise it can pay off, but resource-wise it's a waste. I've put it last in the list now, behind the "useful" cryptocurrency mining like Gridcoin, which is also possible now. – tanius Sep 11 '16 at 23:55
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You could do that. It'd raise the temperature a little bit. However, it's certainly not optimal.

If you're attempting to lower your overall energy use and still be warm, your best bet is to not try to keep the whole house at 70 degrees Fahrenheit (21 Celsius). Turn down your heat to 60 F (16 C), turn off your appliances, and then use a space heater / heat blanket / etc to heat just the immediate area you're using at the time.

  • There are significant potential health risks with lowering a house to 16 degrees C - it's important to work through the psychrometry issues with such a heating regime. – EnergyNumbers Dec 9 '14 at 21:47
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    Do you have any citations for that? Keep in mind that the idea is to keep the people in the house at a higher temperature, by specifically heating where they are, instead of the entire house. – Tom Brendlinger Dec 9 '14 at 23:44
  • @EnergyNumbers just like Tom I'm curious about the potential health risks and psychrometry issues as well. In the winter, we hardly ever heat the bedrooms so these are always at much lower temperatures than the living room. – THelper Dec 10 '14 at 11:15
  • @THelper, Tom, perhaps that is best posted as a question in its own right – EnergyNumbers Dec 10 '14 at 12:02
  • @EnergyNumbers Good idea! I've posted a new question – THelper Dec 11 '14 at 8:38

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