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.

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.

All our devices offer several heat levels you can choose from.

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.

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.

All of our heaters and miners are CE compliant. They have been tested against the relevant European safety standards.

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.

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.

Please contact our support 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.

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.

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.

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.

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.

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.

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.

Please feel free to submit an inquiry through our contact form on the website. Please provide all necessary information so that we can process your request as efficiently as possible.

Yes, we have specific pricing tiers for certain products starting from a certain quantity. Please feel free to send us an inquiry through our contact form for more information.

Please feel free to email us at office@21energy.com and we will get back to you.

Please have a look at our open positions.

Yes, there is a USB port on the back of the Ofen 2, through which you can connect a LAN cable using a suitable adapter.

The Ofen 2 can be controlled via the 21energy App. You can turn it on and off, adjust the heating levels, connect it to a thermostat, create schedules, and integrate it into your Home Assistant setup.

A Bitcoin wallet is required if you want to store the earnings from your mining pool yourself. Alternatively, you can send the earnings directly to an exchange and have them paid out in euros.

The Bitcoins mined by the Ofen 2 are first credited to your mining pool account. From there, you can transfer them to your Bitcoin wallet or directly to an exchange. More details can be found in theuser manual, section 5.4.

The Ofen 2 requires very little bandwidth (<1 Mbit/s). The most important factor is that the connection is stable and reliable.

This is not recommended by default and should only be done if the Ofen 2 is placed and secured carefully and safely. The wall mount is designed only for horizontal installation.

Yes, there is a USB port on the back of the Ofen 2 Pro, through which you can connect a LAN cable using a suitable adapter.

The Ofen 2 Pro can be controlled via the 21energy App. You can turn it on and off, adjust the heating levels, connect it to a thermostat, create schedules, and integrate it into your Home Assistant setup.

A Bitcoin wallet is required if you want to store the earnings from your mining pool yourself. Alternatively, you can send the earnings directly to an exchange and have them paid out in euros.

The Bitcoins mined by the Ofen 2 Pro are first credited to your mining pool account. From there, you can transfer them to your Bitcoin wallet or directly to an exchange. More details can be found in theuser manual, section 5.4.

The Ofen 2 Pro requires very little bandwidth (<1 Mbit/s). The most important factor is that the connection is stable and reliable.

This is not recommended by default and should only be done if the Ofen 2 Pro is placed and secured carefully and safely. The wall mount is designed only for horizontal installation.

A hydro-cooled ASIC miner is connected to your central storage tank instead of an oil or gas burner. It runs Bitcoin computations and turns nearly 100% of the electricity into heat, warming the water that feeds your radiators, underfloor heating and hot water, while the computing earns you Bitcoin.

Both. With around 7 kW of output and outlet temperatures of 70 °C and above, it can be the primary heat source for a single-family home. You can also run it as a smart add-on alongside an existing heat pump, gas or oil boiler.

Yes. It's retrofittable, it connects to standard storage tanks and water-based heating circuits and works with both radiators and underfloor heating. There's no need to replace what already works.

About the same as any electric heater: near 100% of the electricity becomes usable heat. The difference is that this one also earns, part of your heating bill comes back to you as Bitcoin Cashback, paid out daily and fully transparent.

No, it works on any electricity supply. If you do have solar, you can mine with your PV surplus instead of feeding it into the grid, for up to 5× the return of a standard feed-in tariff.

It's engineered and made in Austria and launches in Q4 2026. Join the waitlist to be first in line and get notified the moment it's available.

No. All our miners ship from our warehouse in Austria. Customers inside the EU (including Germany, Austria, France, Finland, Sweden, and more) pay no customs or import duties. The shop price is the final price.

Customers outside the EU will pay country-specific import duties on delivery, we only display the net price for such orders.

In-stock miners typically arrive within 2–3 business days across the DACH region.

For pre-orders or custom configurations, the expected lead time is stated directly on the product page. All orders over €200 inside the EU qualify for free shipping.

All new, originally packaged ASIC miners we sell come with a 12-month warranty, provided the operating conditions (ambient temperature, power supply, no overclocking) are observed.

Repairs or replacements are handled directly through our European support, no return to China or the US required.

Technically, every ASIC miner converts ~100% of its electricity into heat, that is the physical reality. For residential heating use, we recommend our Ofen 2 series: insulated housing, quiet operation, designed as furniture, and a control app.

Plain ASIC miners (e.g. Antminer S21) can also be used as a heat source for basements, offices, or workshops, but they are louder and less living-room friendly.

We accept SEPA transfer, credit and debit cards (Visa, Mastercard), Apple Pay, Google Pay, Klarna (pay-over-time), and of course Bitcoin.

For B2B orders and larger quantities, we offer custom payment terms, contact our business team for details.