02 · from the workshop
- Heat output: 2.0 kW
- Suitable for rooms up to: 100 m²
- Hashrate: 80 TH/s
- Efficiency: 20 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 Base XL: heat your room and mine bitcoin at the same time
The 21energy Ofen 3 Base XL is built for spaces where 1 kW isn't enough: a workshop, a garage where you tinker, a studio, a practice room or a large open-plan kitchen. With 2 kW it heats up to 100 m², and the 80 TH/s of mining chips that produce that heat work on the Bitcoin network in the meantime. The XL housing is wider and lower than the slim Base and runs at 40 dB, audible like a quiet fan. In a workspace, that's no problem.
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 (2.0 kW × €0.30) | €0,60 |
| Mined (80 TH/s) | about €0.11 |
| Net electricity cost | about €0.49 |
| Regular 2.0 kW electric heater | €0,60 |
| 2.0 kW of heat from gas | about €0.30 |
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.
Base XL or Pro XL?
Same housing, same noise, almost the same heat. The Base XL has 80 TH/s at 20 J/TH, the Ofen 3 Pro XL 120 TH/s at 17.5 J/TH and 2.2 kW. The Pro XL costs about 1,100 euros more and gets a third more hashrate per kilowatt-hour. If the heater runs for hours every day in a commercial space, the Pro XL is the better choice. For a garage where you tinker on weekends, the Base XL is more than enough.
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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