Air heat pump LWZ504 or WPF10 ground heat pump

Hello everyone,

I hope you can help me a little.

The following key data is available:

New build mid 2016 – solid house Kfw55 – in Bavaria Augsburg
Roof 45 degrees south-facing with 6kwp photovoltaic
260m² underfloor heating
With controlled residential ventilation
Currently 2 people, later 4

From the energy consultant I received the following:

Heating demand 16760 kWh/a
Specific heating demand 41.3 kWh/(m²a)
Specific final energy demand 9.7 kWh/(m²a)
Specific primary energy demand 23.3 kWh/(m²a)
Building volume 1268 m³
Usable or net floor area 405 m²
Thermal envelope 964.9 m²
A/V ratio 1/m 0.76
HT' W/(m²K) 0.219
Standard heating load according to Din 4108-6 (KW) 17.4

Which system would you prefer? Stiebel Eltron LWZ504 or WPF10 ground-source heat pump with a Zehnder350 ventilation system?
Currently, the price difference is around €7000, with the LWZ being cheaper.

A large garden is available. A 500 m² surface collector with self-performance would be possible (excavation work would be free—except for diesel).

If you deduct the Bafa subsidies, the LWZ would be about €4000 cheaper.
Considering the savings of €150-200 per year, the WPF10 would pay off after 20 years. Also, you would have to pay attention to planting etc. and have the extra work of installation.

What would you do?

Regards Florian

With a ground-source heat pump, you improve the yield per kWh of electricity. You have to use your own crystal ball to see how the electricity price will develop in the future. Then you can better assess whether the additional cost is worth it for you.

You should also compare the assumptions of the energy consultant with your usage behavior. They usually assume (normally) 20°C room temperature; if you want more, heating costs will increase.

Personally, I would choose a ground-source heat pump if it technically works on the property. Especially for such a large house.