02 · from the workshop
- Heat output: 2.2 kW
- Suitable for rooms up to: 110 m²
- Hashrate: 120 TH/s
- Efficiency: 17.5 J/TH
- Noise level: about 40 dB
- Dimensions (w × h × d): 63 × 83 × 16 cm
- Weight: about 28 kg
- Power connection: regular wall outlet, 230 V
- Network: Wi-Fi
- Controls: 21energy app (iOS, Android), Home Assistant, open API
- Thermostat: yes, via the included RuuviTag
- Colors: white, black
- Warranty: 12-month manufacturer's warranty plus statutory rights
- Delivery time: 3 to 5 business days
- Made in: Austria
Buy the 21energy Ofen 3 Pro XL: heat your room and mine bitcoin at the same time
The 21energy Ofen 3 Pro XL is the flagship of the series: 2.2 kW for spaces up to 110 m² and 120 TH/s at 17.5 J/TH. That's the hashrate of three Base heaters in one device, and the most sats per kilowatt-hour in the whole series. It's made for places where the heater runs long and often anyway: a workshop, a large open living space, a showroom, a home office or a small commercial hall. Same XL housing as the Base XL, 40 dB, in white or black.
How the Ofen 3 works
A bitcoin miner turns almost all the electricity it uses into heat; that's physics, not a side effect. 21energy builds a heater around it: chips in a closed housing with a quiet fan, warm air out the top, and in the meantime the miner works on the Bitcoin network. You set it up in three minutes with the 21energy app: connect to Wi-Fi, enter your pool details, done. Schedules, a thermostat via the included RuuviTag, Home Assistant and an open API are all built in. The mined bitcoin arrives in your pool account and you send it on to your own wallet.
Honest about the costs
At the average Dutch electricity rate, electric heating costs more than gas or a heat pump, even with a miner inside. The Ofen 3 is, however, the cheapest way to heat electrically, because every other electric heater gives nothing back. It fits three situations: solar panels with a dynamic contract, a room without central heating (garage, workshop, studio, tiny house), or you're a bitcoiner and you simply want one. Heating a regular home with gas and mainly looking to save money? Then this isn't your product, and we'd rather tell you now than after delivery.
| Per hour at full power | |
|---|---|
| Electricity (2.2 kW × €0.30) | €0,66 |
| Mined (120 TH/s) | about €0.17 |
| Net electricity cost | about €0.49 |
| Regular 2.2 kW electric heater | €0,66 |
| 2.2 kW of heat from gas | about €0.33 |
Reference date late August 2026: electricity €0.30 per kWh, hashprice 38 USD per PH/s per day, 1 USD = 0.90 EUR, gas €0.15 per kWh of heat. The hashprice moves daily with the price and the network, so what you mine is never a fixed amount. What is certain: the Ofen uses exactly as much as a regular heater of the same power, and everything the miner earns comes off that. The full calculation is on the category page bitcoin heating.
Who the Pro XL is the right choice for
Buy the Pro XL if two conditions are met: your space really needs 2 kW or more, and the heater will run for many hours. If only the first is true, the Base XL is 1,100 euros cheaper and heats almost the same. If only the second is true, the Ofen 3 Pro in the slim housing is probably a better fit. Two Ofen 3 Pros spread over two rooms are often more practical than one Pro XL in a hallway.
All four models side by side
| Model | Heating | Space | Hashrate | Efficiency | Noise | Price |
|---|---|---|---|---|---|---|
| Ofen 3 Base | 1.0 kW | up to 50 m² | 40 TH/s | 20 J/TH | 35 dB | €1999,00 |
| Ofen 3 Pro | 1.1 kW | up to 55 m² | 60 TH/s | 17.5 J/TH | 35 dB | €2799,00 |
| Ofen 3 Base XL | 2.0 kW | up to 100 m² | 80 TH/s | 20 J/TH | 40 dB | €2899,00 |
| Ofen 3 Pro XL | 2.2 kW | up to 110 m² | 120 TH/s | 17.5 J/TH | 40 dB | €3999,00 |
What's in the box
- The Ofen 3 itself, in white or black
- Basic stand to set it up freestanding
- RuuviTag temperature sensor for the thermostat function
- Power cable for a regular wall outlet
- Quick start guide
A wall mount or the premium stand is sold separately.
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