Energy efficiency at the highest level: The KfW 40+ home is heated using just one LAMBDA EU 13L heat pump.
In 2023, a modern apartment building with three residential units and a total living area of 519 m² was constructed in Heilbronn. For Dipl.-Ing. Johannes Ehnes, it was clear from the start: a heat pump would handle the entire heating and hot water supply—energy-efficient, durable, and future-proof.
Mr. Ehnes had already had very positive experiences with a heat pump in his previous home, so his standards and expectations for a new heat pump were correspondingly high. Designing the new building as a KfW 40+ home also imposed even higher requirements: low energy performance ratings, minimized primary energy demand, and intelligent building technology.
Based on the thorough and comprehensive consultation provided by Mr. Sommer of Kälte GmbH Industrielösungen, the homeowner chose the LAMBDA EU 13L.
Key Technical Specifications of the Project
Property Type | New construction – Multi-family home (3 units) |
Location | Heilbronn, Germany |
Year of construction | 2023 |
Occupied since | April 2024 |
Specialist partner | Christian Sommer, Kälte GmbH Industrial Solutions |
End customer | Johannes Ehnes, B.S. in Engineering, Heilbronn |
Heat pump | LAMBDA EU 13 L |
Heating load | 15.6 kW |
Annual performance factor (APF) | 5.94 |
Energy efficiency class | KfW 40+ |
Energy Performance Certificate | Final energy demand: 16.30 kWh/(m²a) Primary energy demand: 14.70 kWh/(m²a) U-value: 0.25 W/(m²K) |
Technical Implementation in Detail
Heating area | 519 m² (underfloor heating with 10 cm pipe spacing) |
Hydraulics | Thermal actuators |
Supply temperature | maximum 28 °C |
PV system | 10 kWp with 10.24 kWh BYD battery storage |
Cooling mode | active cooling possible (consumption 148 kWh in the first year) |
Challenges during the construction phase
An incompletely installed ETICS (External Thermal Insulation Composite System) during the winter months caused the heat pump to temporarily reach its performance limits. At that time, the facade insulation had only been partially installed, which made it difficult to maintain a stable temperature on the construction site. The “Connected Heat” remote monitoring system proved to be a valuable asset, particularly during the screed drying phase. The ability to continuously monitor the system remotely ensured that any malfunctions or insufficient temperatures could be detected early on—a decisive advantage. Without this functionality, numerous manual checks would have been necessary. This ensured efficient operation and prevented unnecessary delays in the construction process. Even under these circumstances, the system remained reliably operational—a testament to the robustness of the LAMBDA EU13L.
Energy consumption in the first year of operation
(April 2024 – March 2025)
Month | Heat pump consumption [kWh] |
|---|---|
| April | 380 |
| May | 171 |
| June | 126 |
| July | 232 |
| August | 185 |
| September | 145 |
Month | Heat pump consumption [kWh] |
|---|---|
| October | 485 |
| November | 810 |
| December | 1167 |
| January | 1316 |
| February | 1026 |
| March | 704 |
| Total | 6,747 kWh |
Distribution according to heat pump
- Heating: 4,749 kWh
- Hot water: 1,850 kWh
- Cooling: 148 kWh
“I already had a heat pump in my previous home and was very satisfied with it. For my new KfW 40+ project, it was clear to me: a heat pump was the only option. Mr. Sommer from Kälte GmbH highly recommended the Lambda heat pump to me. I followed his advice—and I’m absolutely satisfied.”
