The Payback Calculation
At €808/winter earnings (21energy's published figure based on 1-year BTC average), the payback period for the Ofen 2 Pro at €2,490 is approximately 3.1 heating seasons. From season 4 onwards, every winter's earnings are pure profit — and you're still heating your home for free.
Bitcoin Price Scenarios
Bear case (BTC at £30,000): ~€400/winter earnings. Payback ~6 seasons.
Base case (BTC at £60,000): ~€808/winter earnings. Payback ~3 seasons.
Bull case (BTC at £120,000): ~€1,600+/winter earnings. Payback ~1.5 seasons.
The honest truth: if you believe Bitcoin will be higher in 3–5 years than today (as most Bitcoin holders do), the payback case is strong. If you think Bitcoin will be lower, the maths is less compelling.
What About UK Electricity Costs?
UK electricity at 24p/kWh is higher than the EU average. This means two things: your heating costs are already high (making the offset more valuable), and the kWh cashback calculation will reflect a different rate than the Austrian market. The key number to know is your own electricity tariff — plug it into 21energy's calculator for a personalised estimate.
The Bottom Line
A Bitcoin heater doesn't pay for itself through savings — it pays for itself through earnings. You spend the same electricity whether you use a 21energy heater or a conventional one. The Bitcoin you earn is incremental income on top. If you'd buy an electric heater anyway, the upgrade cost to a Bitcoin heater is the real investment question. On that basis, the payback case is genuinely compelling for anyone with a positive Bitcoin outlook.
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.