What Is The 21energy Ofen 2 Pro?
21energy is an Austrian startup that had a simple but brilliant idea: Bitcoin mining hardware generates a lot of heat. Electric heaters convert electricity to heat. Why not combine them? The Ofen 2 Pro is the result — a product that looks like a premium designer radiator and works like one, but the heat it generates comes from Bitcoin mining rather than a conventional heating element.
The company was founded in Innsbruck, Tyrol. They've sold to over 5,000 customers, hold a 4.8-star Trustpilot rating, and have been featured on ORF, n-tv and BLOCKTRAINER. This isn't a startup nobody's heard of — it's a proven product with real customers and real reviews.
Build Quality & Design
The Ofen 2 Pro is available in white or black. Both are genuinely attractive pieces of hardware — nothing like the industrial look of a typical ASIC miner. The housing is solid, well-finished, and designed to sit in a living room without looking out of place. 21energy clearly invested in industrial design and it shows.
The unit is made in Austria, which matters for quality assurance. Every Ofen is tested before shipping. The 30-day money-back guarantee gives you confidence that 21energy stand behind the product.
Heating Performance
The Ofen 2 Pro outputs 1.1 kW of heat — suitable for a room of approximately 10–15m². It heats effectively and consistently. The output is comparable to a conventional 1,100W electric panel heater. The difference is that a conventional panel heater costs you money to run — the Ofen 2 Pro earns you Bitcoin while it's doing exactly the same job.
Bitcoin Earnings — What Can You Actually Expect?
This is the question everyone asks. 21energy's own calculator shows €808 per winter based on a 1-year Bitcoin price average and 180 days of heating season. That's based on:
- €0.17/kWh cashback rate per kWh of electricity consumed
- 1.1 kW/h power consumption
- 24 hours per day × 180 days heating season
The honest caveat: Bitcoin price is volatile. Your actual earnings will vary with BTC price movements. At higher Bitcoin prices, earnings could significantly exceed €808. At lower prices, they'll be less. The electricity cost is what you'd spend on any electric heater anyway — the Bitcoin is the bonus.
Payback period at €808/winter earnings: approximately 3 heating seasons to recover the purchase price of the Ofen 2 Pro. From season 4 onwards, you're in profit — and still heating your home.
Noise Levels
ASIC miners are notorious for noise — data centre machines are often as loud as jet engines. The Ofen 2 Pro is whisper-quiet by comparison. 21energy has engineered the housing and fan configuration specifically for domestic use. Multiple customer reviews confirm it's acceptable for living room use. Not completely silent, but nowhere near industrial mining hardware.
Scores
| Build Quality | 9.5/10 |
| Heating Performance | 9/10 |
| Bitcoin Earnings | 8.5/10 |
| Noise Level | 8/10 |
| Value For Money | 8/10 |
| Overall | 4.7/5 |
Who Is The Ofen 2 Pro For?
- Anyone already interested in Bitcoin who wants a productive way to participate in mining without a dedicated mining setup
- Homeowners who heat with electricity and want to offset their energy bills
- Crypto enthusiasts who want a non-custodial, self-managed Bitcoin earning device
- People who want to understand Bitcoin mining without industrial hardware
- Businesses wanting to heat premises while mining — see our B2B guide below
Who Is It NOT For?
- People who heat with gas — the economics work best when you're already using electric heating
- People who need guaranteed heating output — Bitcoin price volatility means earnings vary
- Anyone expecting a traditional radiator — this requires WiFi setup and Bitcoin wallet configuration
Sento is the UK ordering point for 21energy products. Prices match the official 21energy website. Earnings figures are estimates based on 21energy's calculator and historic Bitcoin averages — actual earnings will vary with Bitcoin price. This is not financial advice. Updated March 2026.