The principle is simple: the outdoor unit extracts heat from the air and transfers it to the water in your heating system. It works even in freezing weather – air holds usable energy down to around -25 °C. This is the most common type of heat pump – no borehole, ground collector or well needed. All you need is space for the outdoor unit and a connection to your house.
What to expect
- Heating – underfloor, radiators, fan coils
- Cooling – active cooling in summer (reverse cycle)
- Hot water – year-round DHW production
- 50–70 % savings compared to electric heating
- Webserver – remote control and diagnostics via the internet
Who is it for
Family houses, apartment buildings, commercial properties. Anywhere you want a straightforward installation with no groundwork. Models from 3 kW (small flat) up to 50 kW (commercial building) – and even more with cascade setups.
What’s included
With HOTJET you don’t pay extra for “feature packages”. Everything is standard: Siemens controls (3 circuits), photovoltaic support, wood boiler / fireplace backup, hybrid function, pool heating, active cooling and a webserver with mobile app with a lifetime licence.
Flagship: ZETXp series with R290
The new generation with natural refrigerant R290 (propane, GWP 3). Copeland YHV scroll inverter compressor, output temperature up to 75 °C, energy class A+++/A+++. Models at 7, 10 and 15 kW with real output up to 10, 15 and 25 kW.
Indoor variant: ZETXi
Can’t place an outdoor unit? ZETXi sits entirely inside the building – air is ducted through the facade. Nothing visible outside at all. Ideal for listed buildings, apartment blocks or locations with strict noise regulations.
Heat Pump Explorer
Air–Water 7 · 10 · 15 kW 
Air–Water 7 · 10 kW Air–Water 15 · 20 kW 
Air–Water 10 · 15 kW 
Ground–Water 7 · 10 · 15 kW 
Water–Water 7 · 10 · 15 kW 
Air–Water 5 kW 
Air–Water 20 · 25 · 35 · 45 · 55 kW 
Accessories 70 kW 
Accessories 
Accessories 
Hybrid 10 + 25 kW