Warmth that pays off.
The heater Ofen 2 Pro warms your home and generates cashback.
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What customers say
5, 000+ satisfied customers and trusted by thousands of homes across Europe.
Verified
The app (iOS) is well made and feels intuitive, the heater itself is very quiet even when running at its maximum power. I have using it for 5 days now and so far I'm very happy. I almost never write reviews but this company deserves to get recognition
Daniel Garcia
January 14, 2026
Verified
Excellent service as always! Thank you again 😊
JonnyW
February 5, 2026
Verified
Had an error at first but to be fair they did everything to rectify it and put it right and more
andrew ferguson
April 2, 2026
Verified
Perfect ! I receive everything and travel was long. Thx to all team !
Vivien Gaillard
January 8, 2026
Verified
Top Support 👍
Alex Tornyossy
March 23, 2026
Verified
all good, works well, good support.
Fredrik Åhslund
December 22, 2025
Verified
Ofen 2 is good product and there is a good service support. The product is well designed and well manufactured. I got a minor bug issue at the beginning with the thermostat. Support solved it very quickly with an update.
Jidé Jidé
December 4, 2025
Verified
Awesome Team. Had a great conversation with a customer service agent, helped me understand the inner workings of mining!
Remington Splettstoesser
September 24, 2025
Ofen 2 explained
Austria
Ofen 2 explained
Austria
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Efficient by design
Quiet warmth
Whisper-quiet (~35 dB) so it blends into your living room.
Cashback
77 high performance processors turn electricity into warmth and Bitcoin.
Desired temperature
Set your desired temperature and the thermostat maintains it day & night.
Built to last
Premium aluminium for long life and low maintenance.
Touch-safe design
Enclosed heating core and rounded edges, CE certified.
Quiet warmth
Whisper-quiet (~35 dB) so it blends into your living room.
Cashback
77 high performance processors turn electricity into warmth and Bitcoin.
Desired temperature
Set your desired temperature and the thermostat maintains it day & night.
Built to last
Premium aluminium for long life and low maintenance.
Touch-safe design
Enclosed heating core and rounded edges, CE certified.
Made in Austria
See it in action
Details in a nutshell
Ofen 2 Pro
Ofen 2
Which heating saves you the most in {country}?
Austria
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Good for the environment
The operation of the Ofen 2 can save up to 3 tons of CO₂ per year compared to conventional heaters.
Set up in 3 minutes using the app.
Dive into the specifics
Discover our innovative Bitcoin heaters and find out how it helps you to heat more efficiently and save money.
Coming in 2026
Bitcoin Central Heating.
Heat your home, your water & earn Bitcoin all year long. Even more profitable with solar.
Questions & Answers
Shipping
When will my products be delivered?
We typically ship all products within 2-3 business days. Following that, your order will reach you within a few business days, depending on the delivery location. Any pre-orders or delays will be indicated in the description or in a separate message.
In which countries does 21energy ship to?
Currently, we ship to the EU, Switzerland, Norway and Great Britain. If you want to find out if we deliver to your address, you can easily test this in the checkout process by entering your address there.
What are the shipping costs for me?
The shipping costs vary depending on the delivery location. To calculate your personal shipping costs, you can go through the checkout process. After entering the delivery address, the costs will be displayed to you. All orders over €200 qualify for free shipping!
Are there any additional costs for customs or taxes?
For all customers within the EU, there are no additional costs due to taxes and customs. All customers outside the EU pay only the net price in the store when ordering. Therefore, taxes and duties will be incurred upon import and are to be paid there.
Can I cancel my order?
Yes, every customer has a 30-day right of withdrawal. Within this period, you can cancel your order without providing any reasons. The paid amount will be refunded to you via the originally selected payment method.
Income
How do the 21energy heaters and computers (mining devices) make money?
21energy heaters and computers (mining devices) generate revenue through the process of Bitcoin mining, wherein specialized hardware solves cryptographic puzzles to validate and secure transactions on the blockchain network. As a reward for their computational work, miners receive newly minted bitcoins and transaction fees.
How much can I earn from heating with the heaters or other mining devices?
Your mining earnings depend on various factors such as the price of Bitcoin, market rates for computations, global hashing power, duration of operation, and hardware model. For your individual situation, we have developed a profitability calculator. The significant distinction from any other electric heater is that cash flow is generated while heating.
Performance
Do the different products require more electricity than traditional heaters?
No, these products do not require more electricity than traditional heaters. They efficiently convert 100% of the electrical energy into heat, simultaneously utilizing it to mine Bitcoin, effectively leveraging energy in a dual capacity.
Does my electricity bill change with 21energy products?
If the same heating method (electric heating) with the same heat demand is applied as before, the electricity bill usually does not change, as the entire electrical energy continues to be converted into heat.
Can the heating power be adjusted on the individual devices?
All our devices offer several heat levels you can choose from.
How much heating area do 21energy products cover?
The heating area of each heater is specified in the product descriptions, which may vary significantly depending on their characteristics. For all individual hardware devices, the heating area can be determined using various calculators available online, based on the specified power output.
Are the products allowed to be overclocked to achieve maximum yield?
Our heaters are only allowed to be operated at the maximum power specified in the description and/or user manual. Overclocking poses a high risk and will void the warranty immediately. Similarly, each individual Bitcoin mining device should only be operated at its maximum standard power.
Safety & Warranty
Your device is built to run in the configuration it was delivered in. The points below help your heater or miner run safely and reliably. Please keep one thing in mind for all of them. If a device is operated outside its specification and this causes damage, that damage does not count as a product defect, and our voluntary manufacturer's guarantee does not cover it. Your statutory legal rights still apply to any fault that was not caused by this kind of operation.
Safety and compliance
Are the devices CE compliant and safe?
All of our heaters and miners are CE compliant. They have been tested against the relevant European safety standards.
Is there protection against overheating?
Yes. Our devices run an operating system that constantly monitors the temperature and shuts the device down once it reaches the defined limit. This protection can only do its job when the device is operated within its specification. The airflow must not be blocked and the dust filter has to be kept clean, as described in the user manual. The protection also needs the firmware that we install at the factory. Third party firmware or changed temperature settings can switch it off.
Warranty
Is there a warranty on 21energy products?
We give a voluntary manufacturer's guarantee of 12 months from the date of purchase. It covers faults in material and workmanship, as long as the device was installed and operated according to the user manual. This applies to our heaters and to the Bitcoin miners we sell, both new and refurbished. This voluntary guarantee is in addition to your statutory consumer rights and does not limit them.
How do I return a device if there is a problem?
Please contact our <a href="https://21energy.com/pages/support">support</a> first and we will arrange the next steps with you. When you send a device back, please use its original packaging so it is protected during transport.
Operating within the specification
At what power should I run my device, and may I overclock it?
Please run your device at the default power that is stated in the product description or in the user manual. Running it above its factory default settings, for example by raising the clock speed or voltage to get more power, is called overclocking and is operation outside the specification. This puts heavy stress on the hardware and can damage it for good. You should also never turn off the protective functions. If overclocking causes a defect, the principle described above applies.
May I install different or custom firmware?
We strongly advise against installing different or custom firmware. The device is set up to run on the firmware that we install before delivery, and that is how it is meant to be used. Custom firmware is mostly used to overclock or to change voltage and temperature settings, which takes the device outside its specification and can damage it. If you still choose to install it, you do so at your own risk. Custom firmware voids the voluntary manufacturer's guarantee, and any damage it causes does not count as a product defect. Faults that have nothing to do with the firmware change are not affected.
May I replace hardware parts or repair the device myself?
Please do not open the device or change its hardware. Opening the device or changing any of its parts takes it away from the condition it was delivered in, and the same goes for repairs you carry out yourself. If something is wrong, please contact our support first and we will find the best solution together with you. If an unauthorized change or repair causes a defect, the principle described above applies.
In which environment may I operate the device?
You will find the allowed temperature and humidity for your device in its user manual. Please keep the device within these conditions at all times so that it runs safely and reliably.
What should I pay attention to with the power supply?
Miners and heaters are sensitive to an unstable supply and to incorrect fusing. Please make sure the power supply is stable and correctly fused, and that it is connected the way the user manual describes, so that your device is protected against problems coming from the grid.
Hydro and immersion cooling
May I start a hydro miner without a cooling loop?
No. A hydro cooled miner may only run inside a closed cooling loop that is properly filled. If you start it without a connected cooling system, it can be damaged beyond repair within a very short time. Always check that the cooling loop is connected and filled before you start the device.
Which coolant and which values do I need on a hydro miner?
Use only the coolant that the manufacturer recommends and keep the water temperature, the flow rate and the pressure within the limits given in the manual. A good choice is deionized or distilled water with a corrosion inhibitor and a biocide. You can also use a ready mixed non conductive coolant. Please follow the pH value that the manufacturer specifies. Tap water or running the system outside the specified values can damage the device.
May I convert my device into an immersion miner?
Air cooled devices are not made for immersion cooling. Converting one so that it can be submerged in fluid is technically demanding, and even a small mistake with the fluid or the conversion can cause a short circuit and damage the device beyond repair. A conversion like this is operation outside the specification, and the principle described above applies to any damage that results from it. If you want to run immersion, please talk to us first, because there are devices that are built for it.
Business
I would like to partner with you. What options are available? Is it possible to collaborate with 21energy as a distribution partner?
Please feel free to submit an inquiry through our <a href="https://21energy.com/pages/business-solutions#contact" title="https://21energy.com/pages/business-solutions#contact">contact form</a> on the website. Please provide all necessary information so that we can process your request as efficiently as possible.
Are there special pricing tiers for larger quantities?
Yes, we have specific pricing tiers for certain products starting from a certain quantity. Please feel free to send us an inquiry through our <a href="https://21energy.com/pages/business-solutions#contact" title="https://21energy.com/pages/business-solutions#contact">contact form</a> for more information.
Is it possible to invest in 21energy?
Please feel free to email us at <a href="mailto:office@21energy.com" target="_blank">office@21energy.com</a> and we will get back to you.
Are there any open positions at 21energy currently?
Please have a look at our <a href="https://21energy.com/pages/careers#jobs" title="https://21energy.com/pages/careers#jobs">open positions</a>.
