Hybrid Heat Pump Hotjet H25/10 with Pellet Boiler
- Type: Hybrid (pellets + heat pump)
- Boiler output: 25 kW
- Heat pump output: 10 kW (at 0 °C)
- Fuel: Wood pellets
- Control: SIEMENS
- Energy class: A+
- Emission class: 5
Two heat sources in one unit
The Hotjet H25/10 is a 25 kW pellet boiler and a 10 kW air-to-water heat pump in a single cabinet. Siemens control compares the cost of heat from both sources and switches to the cheaper one. You don’t need to manage anything.
Ground-to-water principle inside the hybrid. The heat pump in the H25/10 works externally as air-to-water, but internally it’s ground-to-water. The outdoor unit is connected to the indoor block via a glycol loop and collects heat from the air. The heating water never leaves the system. So even if you shut down the heat pump completely, nothing freezes. And the compressor sits indoors, protected from the weather.
Instead of the outdoor unit, you can connect the primary circuit to a ground collector or borehole and get a full geothermal heat pump. Or use it for heat recovery from the building. In summer, it can also provide active cooling.
At −10 °C the entire system delivers up to 35 kW. A comparable standalone heat pump would cost more. And it would need a higher-rated circuit breaker with a higher monthly fixed charge. The H25/10 draws less electricity because the pellet boiler takes over in freezing conditions. Smaller breaker, lower distribution fees, lower bills.
How it works
The heat pump heats on its own for most of the season. When the outdoor temperature drops and the COP falls below the point where electric heating is cost-effective, the control starts the pellet boiler. It also factors in the tariff — during off-peak electricity, it lets the heat pump run longer even at lower efficiency. Pellets are saved.
Why it makes sense
Both fuels are renewable — pellets and electricity for the heat pump both qualify as RES. Operating costs are 30–40% lower than a boiler or heat pump alone, because each source only runs where it performs best.
You don’t have to buy everything at once. You can start with the pellet boiler and add the heat pump a year or five years later. If there’s a power outage, the pellet boiler keeps heating. The heat pump also lasts longer in hybrid mode because it’s not stressed during extreme cold.
The control manages two mixing heating circuits and domestic hot water heating.
Who is it for
Larger or older houses with a heat loss of 15–25 kW. Properties without gas. Renovations where a pellet boiler with hopper fits in the boiler room. And also for those who don’t want to depend solely on electricity or a single fuel.
More about hybrid heating in the article Hybrid systems – how it works in practice.
| Rated boiler output | 25 kW |
| Heat pump output | 10 kW (at 0 °C) |
| Fuel | Wood pellets |
| Pellet hopper volume | 200 l |
| Dimensions (W × D × H) | 1,680 × 1,172 × 1,291 mm |
| Energy class | A+ |
| Emission class | 5 |
| Ecodesign | Yes |
| SVT certification | 22 126 |
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