SunBit Turns Bitcoin (BTC) Miners Into Home Heaters Across 30 Systems

A Miner Replaces the Oil Boiler

In the Finnish town of Nokia, a 180-square-meter house has left the district heating network and now draws all of its warmth from a single crypto mining rig. The machine sits inside the "Bitcoin (BTC) Boiler" sold by local startup SunBit: every kilowatt-hour the unit consumes comes back out as an equal amount of heat, which SunBit stores in water at up to 60°C and distributes through radiators and underfloor pipes much as an oil or gas boiler would. While the house stays warm, the rig performs the proof of work that secures the network and earns Bitcoin (BTC) around the clock. SunBit's pitch is simple: as long as the coins mined cover the electricity bill, the owner carries no net energy cost and keeps the difference. Installation starts near $20,000, and returns rest on three moving inputs, the Bitcoin price, local power tariffs and the total network hashrate competing for block rewards. Founder and chief executive Elmeri Suomi stressed that the heating itself does not move with the market; only the payback period does. SunBit's model runs on a water-cooled Bitmain Antminer S21 XP Hydro at 495 TH/s with the Braiins OS third-party firmware. The unit draws about 5.3 kilowatts without interruption, some 46,400 kilowatt-hours a year, costing roughly $5,200 at around 11 cents per unit. At an assumed price near $82,000 and network hashrate of 1,040 EH/s, the rig yields about one-twelfth of a Bitcoin (BTC) a year. A subscriber paying SunBit's 10% service fee, with the pool taking another 0.5%, keeps about $6,100; an owner managing the hardware alone keeps the full one-twelfth, worth about $6,800. After electricity, a subscription household clears roughly $900 a year, which makes the warmth effectively free. SunBit places the break-even point slightly below $70,000, about 15% under the price at interview time, and that figure still excludes the cost of the hardware itself. Where the market stands against that line is exactly what our Bitcoin technical analysis tracks.

30 Systems, One in the Netherlands

SunBit shipped its first production batch in 2025 and now operates 30 systems, 29 of them in Finland, each displacing or trimming the use of gas, oil, wood or district heating. The company's published case list lays out the spread: a commercial property in Lekkum, the Netherlands, became the first export in 2025, replacing a gas boiler; a 200-square-meter home in the port city of Kotka runs a rig beside its existing oil boiler; an old estate in Tampere swapped wood heating and holds a 1,500-liter tank at 50°C to 60°C; and a 3,000-square-meter industrial building in Vimpeli pairs a rig with an air-to-water heat pump and surplus power from a 30-kilowatt solar array. Finland had already tested waste-heat recovery at utility scale, with mining firm MARA feeding rig heat into the district networks of Satakunta and Seinäjoki, a setup estimated to reach about 80,000 residents. SunBit's version hands the hardware to the owner, who buys the rig, pays the power bill and keeps the Bitcoin (BTC) earned along the way, which sets these owners apart from the solo Bitcoin (BTC) miners who occasionally win whole blocks on CKPool. The oil-heated comparison shows the money: a detached house burning 2,300 liters of heating oil a year at about $2.19 per liter spends roughly $5,000 on fuel; a rig zeroes that bill and leaves about $920 of mining income after power, about $6,000 a year against an installation price near $20,200, a payback of roughly three and a half years. One early customer runs the cheaper 358 TH/s Antminer S21+ Hydro, which earns about 0.039 BTC a year, worth about $3,160, while displacing some 2,000 liters of oil. Heat pumps remain the harder benchmark, moving 2.5 to 3 units of heat per unit of electricity against the rig's one-to-one. For a home needing 25,000 kilowatt-hours of heat, SunBit estimates a heat pump at about $1,100 a year and district heating at about $3,170, while a rig capped at that demand beats the power bill by about $490. Suomi argues the rig's edge appears in winter, since its output holds even at -25°C. One caveat: over half the heat in the oil-replacement setup never reaches the house, because a dry cooler vents it outdoors, mostly between late May and mid-September. Installed-system payback runs three to six years across installation prices of about $20,400 to $31,400.

The 2028 Halving Math

The arithmetic behind free heating is on a clock. Bitcoin's next halving is expected in spring 2028, cutting the block reward from 3.125 BTC to 1.5625 BTC, and SunBit's model leaves it out. With its other inputs fixed, revenue per kilowatt-hour falls from about 13 cents to about 7 cents, under the 11-cent power price, and the effective cost of heat lands near 4 cents per kilowatt-hour, close to heat-pump running costs. A household installing this winter gets roughly 18 months of the current margin. Free heating after 2028 needs Bitcoin near $131,000, about 60% above last Friday's level, and SunBit's planned grid-balancing services, which would sell interruptible load into the Finnish power market, are the other lever on the model. The record traced here stops at today's 30 installed units; past that point the $131,000 line and any grid revenue remain projections, and no trend beyond the current install base is established.