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1. Bitcoin heating in Finland: how the boiler works
Finnish company SunBit has 30 bitcoin-mining boilers heating buildings as of November 8, 2026, and each machine earns slightly more than its electricity costs while bitcoin trades above roughly $70,000. A mining machine turns every kilowatt-hour it draws into heat, and SunBit, which sells the unit as a "Bitcoin Boiler," captures that heat instead of venting it. Water warmed to as much as 60°C flows to radiators and underfloor pipes in the same way it would from an oil or gas boiler, while the machine mines bitcoin in the background.
The first showcase is a 180-square-metre house in Nokia, the Finnish town that gave the phone maker its name. The household has disconnected entirely from district heating, and its rooms are now warmed by a miner. If the bitcoin the machine earns covers the electricity it consumes, the owners effectively receive heat with no net energy bill.
The arrangement is not a subscription. The property owner buys the machines, has them installed where the old boiler stood, pays for the power and keeps the bitcoin. Because mining rigs are loud, units are placed in a basement or an insulated room. Installation costs about $20,000 or more, and the return depends on the bitcoin price, local electricity prices and the total computing power competing on the network.
2. Why does a bitcoin miner make heat in the first place?
Bitcoin mining is the process by which computers compete to validate transactions and add blocks to the blockchain, and the winner of each block receives newly issued bitcoin. The competition is run by specialised machines performing enormous numbers of calculations every second, and that work consumes electricity. Essentially all of the electrical energy a machine draws ends up as heat, which operators usually treat as a nuisance and remove with fans or liquid cooling.
Heating a building turns that nuisance into a product. A resistive electric heater also converts one kilowatt-hour of electricity into one kilowatt-hour of heat, so a miner is as efficient a heater as an ordinary electric radiator. The difference is that the miner produces bitcoin as it does so. The question for a homeowner is therefore not whether the machine can heat a house, which it can, but whether the bitcoin it earns outweighs the electricity it burns.
That balance moves constantly. Hashrate measures the combined computing power of the network, and as more machines join, the share of rewards going to each one shrinks. The price of bitcoin sets what those rewards are worth in dollars or euros, and local power prices set the cost. Any of the three can shift the result within weeks.
3. Where are the 30 systems installed?
SunBit delivered its first production batch in 2025, and chief executive Elmeri Suomi says 30 systems are now running, all but one of them in Finland. They have replaced or reduced heating from gas, oil, wood and district networks. Suomi's own summary of the pitch is that "the heating itself works regardless of the market, and only the payback time moves."
The sole export project is a commercial property in Lekkum in the Netherlands, completed in 2025, where a miner took over from gas heating. In Kotka, a port city of about 50,000 people on the southeastern coast, a 200-square-metre house runs a miner alongside its oil boiler as a hybrid setup.
In Tampere, Finland's third-largest city, a miner replaced wood heating in an old manor house and feeds a 1,500-litre storage tank held at 50 to 60°C. In Vimpeli, a 3,000-square-metre industrial hall pairs a miner with an air-to-water heat pump, and the combination absorbs surplus electricity from a 30-kilowatt solar array.
Finland has become something of a testing ground for the idea. MARA sends waste heat from its mining operations into district heating networks in Satakunta and Seinäjoki, which together serve about 80,000 residents.
4. What does one miner earn compared with its power bill?
SunBit's online calculator models a single Bitmain Antminer S21 XP Hydro, a water-cooled machine rated at 495 terahashes per second and run on Braiins OS firmware. It draws about 5.3 kilowatts around the clock, which comes to roughly 46,400 kilowatt-hours a year. At about 11 cents per kilowatt-hour, converted from euros at roughly $1.11, the annual power cost is close to $5,200.
The model assumes a bitcoin price near $82,000 and a network hashrate of 1,040 exahashes per second. On those inputs the machine would produce about one-twelfth of a bitcoin a year. After SunBit's 10% service fee, the owner keeps about $6,100, and pool fees take roughly another 0.5%, according to Suomi.
The service is optional. It covers round-the-clock monitoring, optimisation around Finland's spot electricity market and a phone app, with grid balancing planned. An owner who skips it keeps the full twelfth of a bitcoin, around $6,800 a year. With the service, the owner would be about $900 ahead of the modelled electricity bill, before counting the cost of the system. Heat adds no further expense, although a typical house cannot use all of it.
Suomi describes the economics this way: "Mining currently earns slightly more per kWh than the electricity costs." Bitcoin traded near $81,500 on Friday morning, according to CoinDesk data, and SunBit puts the owner's break-even just under $70,000, about 15% lower. That threshold excludes the purchase price of the equipment.
The calculator holds network hashrate constant, so more machines joining the network would reduce each miner's earnings. One early customer with a cheaper 358-terahash Antminer S21+ Hydro mined about 0.039 bitcoin over the past year, worth roughly $3,160, and displaced about 2,000 litres of heating oil. SunBit can see pool data only for its first pilot customers.
5. How does bitcoin heating compare with oil and heat pumps?
Against oil, the case is straightforward. SunBit's worked example is a detached house that burns 2,300 litres a year at about $2.19 a litre, roughly $5,000 in fuel. A miner would eliminate that bill and generate about $920 after electricity under the company's assumptions. Gross mining income is about $6,000 a year against an installed price of about $20,200, which Suomi says carries no extra costs, giving a payback of about 3.5 years before maintenance or financing. The old oil boiler stays in place for the coldest days.
There is a catch: more than half of the heat never reaches the house. An outdoor dry cooler releases the surplus, mostly in summer. According to the Finnish Meteorological Institute, summer in southern Finland runs from late May to mid-September, while deep winter lasts about 100 days in the southwest and 200 in Lapland.
Heat pumps are a tougher rival. They deliver 2.5 to 3 kilowatt-hours of heat for each kilowatt-hour of electricity, whereas a miner delivers exactly one. For a house needing 25,000 kilowatt-hours of heat a year, SunBit estimates running costs of about $1,100 for an air-to-water heat pump and $3,170 for district heating. A miner run only as needed for that load would earn about $490 more than its electricity cost.
The comparison shows where the miner's advantage lies. Heat pumps use far less electricity, while miners use more and offset the bill with revenue, so the edge depends on mining profitability rather than heating efficiency.
Suomi argues that winter favours miners, because output does not depend on outdoor temperature and efficiency does not fall at minus 25°C. Running costs nonetheless track the bitcoin price and network competition, an exposure heat pumps do not share. He puts payback at three to six years for systems costing roughly $20,400 to $31,400 installed.
6. Who is the bitcoin boiler for?
The profile that emerges from the installations is a property with a large, steady heat demand and an existing boiler that burns something costly, such as oil, gas or wood. Hybrid arrangements, like the one in Kotka, let the miner carry most of the load while the old boiler covers extreme cold. Industrial and commercial buildings with spare solar power, like the hall in Vimpeli, can use the machine to absorb electricity that might otherwise go unused.
Households that already run an efficient heat pump are a harder sell. Their heating costs are low, so the extra revenue from a miner has to justify a purchase price of $20,000 or more. As the figures above show, the miner's advantage over a heat pump comes almost entirely from bitcoin income, not from the heating itself.
The ownership model also puts the risk on the buyer. The household holds the hardware, so if bitcoin falls below the break-even level, the heating still works but the bitcoin it earns no longer covers the power bill, and the net cost of heat rises accordingly.
7. What happens to bitcoin heating after the 2028 halving?
A halving is a scheduled event in bitcoin's code that cuts the reward for each new block in half, roughly every four years, and it reduces miners' revenue overnight unless the price rises to compensate. Buyers today are likely to reach the next one, expected in spring 2028, before they recover their costs. The event will cut the block reward from 3.125 bitcoin to 1.5625, halving the new coins miners receive.
SunBit's calculator excludes the halving and prices payback at today's profitability. Suomi declines to forecast: "I personally don't want to give price predictions and difficulty predictions." The company instead explains the effects of past halvings to customers.
With SunBit's inputs held constant, mining income would fall from about 13 cents per kilowatt-hour to about 7 cents, below the 11-cent power price. Heat would then cost about 4 cents per kilowatt-hour, close to the running cost of an air-to-water heat pump. A household installing this winter would get roughly 18 months at current margins.
Keeping heat effectively free after the halving would require bitcoin above about $131,000, some 60% higher than Friday's price. For a few dozen Finnish buildings, the bitcoin price has become part of the heating plan.