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If someone want to heat a room or some water for a defined amount of time and without a worry about the sound produced.

Can a bitcoin miner be a good subtitute to a modern heather with the same power consumption ?

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A device that consumes N watts of power (and doesn't output electricity or some other form of energy) will eventually produce N joules of heat per second.

Thus, if your goal is converting electricity to heat, every piece of hardware that consumes electricity is 100% efficient. It's completely irrelevant what happens with that electricity before it becomes heat.

Of course, you need to take hardware depreciation/maintenance costs into account.

Also of note: as heating devices, heat pumps have over 100% efficiency, as they simultaneously consume electricity (which is turned into heat) and move additional heat from a colder area to a hotter one.

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    A light bulb is a decent example of a device that outputs some of the incoming energy in a different form than heat. If some of the light makes it out a window, that part will escape your house without eventually being absorbed indoors and turning into heat indoors. – Peter Cordes Dec 19 '20 at 15:43
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    And BTW, modern heat pumps often have something like 330% efficiency when not too cold outside. (nrcan.gc.ca/energy-efficiency/energy-star-canada/… - air source heat pumps typically achieve a 3.3 ratio of heat out to input power at 10°C (cool day), or 2.3 at -8.3°C (well below freezing)). So it's not just over 100%, it's much over. Heating your house in winter with some bitcoin mining costs a lot more total electricity, so the coins you mine are not nearly free. – Peter Cordes Dec 19 '20 at 15:52
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    How would it output electrical energy? – Pieter Wuille Dec 19 '20 at 23:52
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    @HamishGibson: True, it will radiate a tiny bit of energy as radio-frequency emissions, from switching in the electronics. Shielding will absorb most of those, i.e. turn that energy into currents in metal which will produce heat via Ohm's law. Some of the energy that escapes the immediate device will be absorbed in your walls. Of course, in English we don't normally call that "electrical energy" - that refers to voltage x charge (and power = voltage x current), not electromagnetic radiation. – Peter Cordes Dec 20 '20 at 0:23
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    @PeterCordes also, there's no such thing as >100% efficiency in thermodynamics. You're talking about "coefficient of performance", which isn't an efficiency, and is thus allowed to be over 100%. – Eric Duminil Dec 20 '20 at 14:21
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It may be practical to use a miner to provide some of the heat for your home, bringing some miners into your home during the cooler months and moving them elsewhere during summer.

It's pretty much 100% efficient at converting electric energy into heat energy. (vs. a heat pump being about 300% efficient1, moving existing heat from outdoors as well). Even a lightbulb that turns some power into visible light will ultimately heat the room when that light is absorbed by the walls. (Unless some light escapes out windows). A fan moves air, but that air movement energy ultimately ends up as heat unless the moving air goes out a window. More-ordered (low entropy) forms of energy naturally convert to high-entropy non-concentrated heat; heating a room is one time the 2nd law of thermodynamics is on your side. (However, the 2nd law is why heat wants to flow from your warm house to the cold outdoors; that's why you insulate your walls.) TL:DR: pretty much any form of energy can efficiently turn into heat.

Footnote 1: Modern heat pumps often have something like 330% efficiency when not too cold outside. According to this Canadian government page about heat pumps, air source heat pumps typically achieve a 3.3 ratio of heat out to input power at 10°C (cool day), or 2.3 at -8.3°C (well below freezing).

So they're about 230 to 300% efficient most of the year. vs. 100% for a fully indoor space heater or computing equipment. Using electric power to run a miner instead of a heat pump is an opportunity cost, if it would be possible to install a heat pump. So the coins you mine have an opportunity cost: you could have gotten more heat for the same power input.


But if you were going to be using electricity to do any mining at all, using the heat output for something useful is good, when possible. If the alternative is putting your mining rig in an uninsulated shed or something and still needing to heat your home, that's worse than having some mining power heating part of your house.

As others have pointed out, you wouldn't want to try to provide all the heating via mining: heating needs are highly variable (depending on weather, sunlight through the windows, and other heat sources like using your oven for cooking), but you normally want your bitcoin mining to be on all the time. (To pay for the initial investment of buying the expensive hardware which costs much more than a dumb space heater; basically just some resistive wire that you put voltage across.)

The amount of mining power you can have indoors in a given month without causing a problem is approximately the best case (smallest) amount of heating that you'll need at any time that month. The rest of the heating load should come from thermostat-controlled regular heating, like a heat pump, oil or gas, or worst case dumb electric heat that just gets hot. (And hopefully that heating system distributes heat around your home better than a miner in one spot, modulo whatever air circulation you arrange to move the mining heat around.)

This "safe" amount of mining might be a few hundred watts, again depending on the month and the size of your home, and if you can hook it up to an existing air circulation mechanism to distribute heat around instead of making one room hot.

If you had more mining power indoors, you'd need some of it on a thermostat, to shut itself down when the room gets above human-desired temperature. (Or put it in an uninsulated basement where it keeps your floors warm, but lots of extra heat can just escape into the ground. Or in the winter, an attic.)

If you have some older less-efficient miners, setting up your computer to stop those first when the temperature rises could make sense. You wouldn't want to buy a lot of mining hardware that would only be on part of the time; that wouldn't be worth the investment. But some semi-obsolete gear could be worth running if the power was effectively cheaper (because you need the heat anyway, and don't have a heat pump).

Bitcoin mining is arguably not a great thing to dump a lot of electrical power into (for environmental reasons), so I'm certainly not suggesting trying to max out your mining by using it to heat your house. Especially if you can get a heat pump instead, and/or your local area doesn't have more renewable energy than it can use (so extra power use means more oil or coal being burned somewhere).

But if you do want to mine anyway, use some of that waste heat in the winter.

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Heat Quality

Not all heat is the same. The earth maintains a fairly constant average of 10 C near the surface, but you can't boil water with that. So the temperature of your heater makes a big difference for the uses you can apply it. If you want your hot water to get to 50 C, but your ASIC miner only generates 40 C of heat, then you are in for a tepid shower at best. On the other hand, if you integrated your bitcoin miners with your HVAC/water heater, you could avoid venting the excess heat. Since your cold water input will almost certainly be much colder than your miners, you can always pre-heat your water with miners, and basically put all your waste heat to good use.

A typical water heater consumes around 12 kWh/day (4 kW x 3 hours). A small miner consumes about 1.2 kW. So in 10 hours, it will generate as much thermal energy as your water heater, more or less. Unless you take a lot of really hot showers/laundry/wash dishes, you should probably buddy up with a neighbor (more convenient in an apartment/condo) to share the excess heat. Of course, you aren't going to make much money with a single miner, but perhaps you could reduce your water heating bill slightly (by investing thousands of dollars in a miner...not really a smart investment).

A room electric heater might consume 1.5 kW and run for 4-6 hours per day, for a usage of 6-9 kWh. That's another 6-7 hours of mining, so you might be able to heat your whole small apartment on one miner.

Return on Investment

For about $1200 you can get an Antminer R4 and 8.6 TH/s at 1.3 kW of power. Your expected Bitcoin revenue for the year with this rig is about $500. If you are able to replace 1.3 kW of electric heating in your home with this rig, you will basically earn $500/yr. towards your electric bill (which is expected to be higher, unless you live in an area with very cheap electricity). It should pay for itself in about 2.5 years (not counting all the work of replacing your heating system with the mining rig, which is probably more expensive than the miner itself).

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Can a bitcoin miner be a good subtitute to a modern heather with the same power consumption ?

A Bitcoin mining rig lacks certain features that are fairly desirable in a room heater. The main one is a thermostat. Even if it did, this would mean you would have to throttle back your Bitcoin miner as the room reaches some desired temperature. You would also need to do less mining in the summer than in winter. Whether reduced mining activity in those situations is acceptable is up to you, of course.

If someone want to heat a room or some water

Heating water is typically a very different proposition. If, for example, you wanted to boil water to make tea, a Bitcoin miner would probably be a very bad place to start.


Although a Bitcoin miner will make a room hot, it isn't going to be particularly good for anything other than what it was designed for.

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    In a cold climate, you'd want some heating most of the year. You could imagine moving your mining rig outside your home during the hot months. If you want to mine at all (instead of running an efficient heat pump or using oil or gas heat), having some of your mining heat output in your home during winter makes sense. Little enough that it won't get too hot if you turn off your other heating during a warm winter day. e.g. some mining heat could just make your regular thermostat-controlled heaters come on less often. And put some in an uninsulated basement that cools itself. – Peter Cordes Dec 19 '20 at 15:57
  • If you want to reduce the amount you spend on heat that doesn't come from mining, you'd have to be willing to throttle the mining somewhat on less-cold winter days, e.g. if you have an older less-efficient miner, that would be the one to shut down first as the temperature reaches the upper end of desired room temp. If the control computer has a temperature sensor, software could do this automatically. – Peter Cordes Dec 19 '20 at 16:02
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    In my experience with using BOINC and Folding@Home to heat my computer room, you don't need precision control of temperature. – Mark Dec 20 '20 at 6:27
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Yes, it is possible to use the waste heat of a bitcoin miner (or any other computing device or other machinery) to heat your living space.

The plan has some drawbacks and limitations:

  1. The temperature: These devices are efficient when they get like ~20C at the inlet and heat air to less than 40C. Trying to make them work at higher temperature may limit their clock frequency and/or useful life. This leads us to:

  2. Noise: You cannot put the miner much further away from the living space. It has to be inside or near (with air ducts). You'll get all the noise. They make a lot of noise.

  3. Control: Unless you are living in some very cold place, you will need to control the heat output from 0 to some value related to your house. There are few methods, but all of them require lowering the mining output. This means lowering the return of investment (and mining is actually quite competitive, so you will end up losing money).

Another variant is to redirect the excessive heat output somewhere else (i.e. outside). Or use the normal means of heating and only supplement it with the miners (if you have a large house and few mining devices)..

  1. Dust These devices require relatively clean environment, or they collect dust. Dust makes them overheat or makes you periodically disassemble and clean them.

What I did in a similar situation: I had to host few servers at home for a while. They ended up in the garage under the house. The heat they generated was beneficial for heating the whole house. The floor was +5..+7C, the noise didn't penetrate the floor and the dust was manageable.

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I highly doubt it. Modern miners nowadays are designed so that they don’t emit too much heat such that they breakdown/ malfunction.

Whilst it is true that they generate a lot of heat, the way in which one could use this as a heating appliance beats me. The engineering required to extract the circuitry and use it as a heating filament is likely to damage the mining equipment as- could become prone to water damage, and- taking it out of its specified structure could cause it to overheat. The remaining air produced from the fan would likely not be as hot as the component due to the law of thermodynamics

Lastly, the degree to which the equipment becomes hot depends on the power drawn, the hash rate, the air humidity and temperature, degradation over time, air impurities etc.

So to summarise, no you can’t heat things with your mining equipment. It would likely damage it and the things you’re heating. And you wouldn’t achieve the outcome you’d desire also.

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    I was interpreting the question as asking about using it as indoor air heating, not as in cooking or anything outputting high temperature. – Pieter Wuille Dec 19 '20 at 0:56
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    Why would any engineering be required at all? – Daniel Wagner Dec 19 '20 at 22:56
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    Energy can't be destroyed, so any energy that you put in has to come out somehow. The only form of energy that is leaving the miner is heat, so it should be almost 100% efficient. The amount of heating that a miner does is just the amount of power that it draws. You don't need extra engineering to extract the heat because if all the heat isn't being dissipated already the temperature of the miner would constantly increase. – BessieTheCookie Dec 20 '20 at 2:12

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