How Do Bitcoin Heaters Work?
A Bitcoin heater is an ASIC miner — specialist computing hardware designed purely to mine Bitcoin — built inside a heater casing. ASIC miners generate enormous amounts of heat as a byproduct of the computational work they perform. Conventional mining setups expend enormous energy cooling this heat away. Bitcoin heaters capture that heat and use it to warm a room instead.
The result: you're using the same electricity you'd use for any electric heater, but instead of just converting it to heat, you're also performing Bitcoin mining and earning rewards in the process.
The Numbers — What Can You Actually Earn?
21energy's own calculator, based on 1-year Bitcoin price averages, shows €808 per winter season from a single Ofen 2 Pro. That's based on:
- €0.17/kWh cashback rate
- 1.1 kW power consumption
- 24 hours per day operation
- 180-day heating season
The key caveat: Bitcoin price is volatile. Earnings will be higher when Bitcoin is up, lower when it's down. But the electricity cost is one you'd incur anyway for any electric heater — the Bitcoin is the bonus.
Is It Right for UK Homes?
UK electricity costs are among the higher in Europe — currently around 24p/kWh on average. This means the opportunity to offset heating costs with Bitcoin earnings is particularly compelling for UK households. The higher your electricity rate, the more valuable the offset.
Bitcoin heaters work best for homes that already heat with electricity (not gas central heating) — flat owners, houses with underfloor heating, or rooms that need supplemental heating. They're not a replacement for a full central heating system.
The 21energy Product Range
21energy currently make three Bitcoin heaters: the Ofen 2 (€2,090), the Ofen 2 Pro (€2,490), and the professional Edge (€6,400). All are made in Austria, carry a 30-day money-back guarantee, and are available to UK buyers through Sento as the UK reseller at the same prices as buying direct from Austria.
Sento is the UK ordering point for 21energy products. Prices match the official 21energy website and are updated regularly. Earnings figures are estimates — actual returns vary with Bitcoin price. Not financial advice. Updated March 2026.