One of the waste products from Bitcoin mining is the heat that is given off by the GPUs. On cold days could this excess heat be used to warm a home, essentially creating a data furnace? When it gets warmer then the rig can be optionally shut down.

As I understand it, the income generated from mining bitcoins at least pays for the electricity so long as you have a rig that is capable of meeting the difficulty. This would therefore imply that so long as you have already got a suitable rig lying around the house (e.g. for gaming) then running it up during the day would be useful. If the house also had solar panels then that would also benefit the earning potential.

Are there any calculations available to support/refute this?

up vote 21 down vote accepted

Yes, you can use a Bitcoin mining rig to heat your home.

Whether or not it's worth doing depends on a number of things, such as:

  • Whether you have a heat pump, or would otherwise install a heat pump (they generally give you 3kW of heat for around 1kW of electricity)
  • Whether of not you have other heating that is more cost effective than electric heating (eg a wood or gas fire)
  • Whether it's convenient to have a mining rig in the location you want heated (you lose efficiency if your heat is produce away from where you want it)
  • The current exchange rate of Bitcoins (and the difficulty of mining them), and how those values change over time for at least the payback period of the mining hardware
  • The price of electricity
  • The noise produced by a mining rig. They tend to be quite noisy, so it may be a disturbance to leave it running overnight
  • Your technical ability to maintain the equipment, and your time available to do so. If it has a problem and you don't have time to fix it, you stop earning mining income.

There's no guarantee that mining earnings will pay for the electricity to run them, let alone pay for the cost of the equipment and the labour incurred maintaining it - this is dependent on the demand for Bitcoins, and your costs. There's always a risk that the exchange rate will drop to the point where it's not worth mining at all, or that new technology (eg ASICs) will make your hardware obsolete before it's paid for itself.

Any web-based profitability calculators that exist won't necessarily take into account all the factors above, and none can predict the Bitcoin exchange rate, so their usefulness will be minimal. I recommend just creating a spreadsheet to do the calculations. To include the value of the heat output in your calculations, consider what you would need to otherwise spend to obtain the same heat output, and include that figure as profit on top of the mining profit (but also of course account for the cost of electricity to run the rig).

To predict the electricity usage of a particular setup, see this hardware comparison - a carefully built rig can run 4 graphics cards which might output 600-800W (or more) of heat. Using a desk fan (or similar) to keep strong air flow on the rig should reduce the potential of a convective flow of air taking the rig's heat straight up to the ceiling, where it won't be felt in cold weather.

  • 2
    Here's a graph that uses the price of $0.15 per kWh blockchain.info/charts/miners-operating-profit-margin It shows a 25% profit margin at current difficulty levels. This is way down from the levels seen in the 1st half of 2011 but is up from the break-even levels (or small losses even) from Oct. and Nov. Mining is just a slightly less risky gamble than buying bitcoins outright. Individual circumstances such as the marginal rate you pay for electricity and the benefit you receive from the heat generated will need to be considered to determine whether or not mining is worth it to you. – Stephen Gornick Dec 20 '11 at 2:13
  • So, a Bitcoin mining thermal power plant is quite possible.. :) – vi.su. Jun 20 '13 at 8:41
  • @vi.su. usually a power plant works the other way round ie generates power! – Highly Irregular Jun 20 '13 at 10:41
  • 1
    @highly-irregular, may be a 'hash plant' that generates hash using heat energy, and produces electricity as byproduct. :) – vi.su. Jun 21 '13 at 10:16

I live in Florida so it's not very cold but when it does dip down I just start mining :D and tuck myself into bed!

By the way, most people have to pay for electricity to heat their homes anyway so the fact you get Bitcoins is just an added bonus to the mining-for-heating!

ASICs might make a data furnace idea easier since they take up much less space to generate high hash rates per watt. The Block Erupter USB project puts an ASIC in a powered USB stick package. Imagine a series of these ASICs coupled to a standard home baseboard radiator heat sink and controlled by a low power Rasberry Pi computer with Wifi to the net.

As long as you are buying a device that breaks even on power, the primary cost factor is upfront cost to buy the hardware. Right now, they cost about $200 per Block Erupter for 300 Mhash/sec at around 3 Watts of power.

At that price, getting to the 1200 Watts typical for a room heater would cost $80K for 400 units. However, you could recoup this investment by selling the bitcoins generated. After deducting power costs, you could recoup the cost in only a year at current difficulty levels. Break even could take much longer than a year though as many ASICs are now hitting the market and will increase difficulty levels. But the point remains that after recouping your hardware cost the heat becomes free.

For those of you living in California this is not a big deal, but free heat to anyone living in Scandinavia would certainly be appreciated.

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