ᐅ Air-to-air heat pump vs. air-to-water heat pump vs. trench ground collector – Differences

face26 schrieb:

If you are willing to do some of the work yourself and enjoy that, and use a trench collector, you might even get a brine-to-water heat pump at no extra cost.

I now see it the same way. If you can contribute your own labor (ideally even do the excavation yourself or have someone who can) and you study how everything needs to be installed, it’s possible to install trench collectors yourself and potentially even “make money back” through the 35% subsidy, unlike an air-to-water heat pump, which typically wouldn’t be eligible for funding (although there are some air-to-water heat pumps now that partially meet the requirements for subsidies). The best approach is to simply plan and get quotes for both options with concrete examples. Especially if you cannot or do not want to do any self-installation, or if trench collectors are not suitable for your property (space, soil conditions, etc.), it will definitely be more expensive. In this forum, I have seen prices for drilling instead of trench collectors ranging from 8,000 to 12,000 EUR, to enable the use of a brine-to-water heat pump.

In general, you should also keep in mind that many costs for air-to-water or brine-to-water heat pumps that achieve an efficiency level of an annual performance factor (APF) of at least 4.5 can be subsidized at 35% through the BAFA (German Federal Office for Economic Affairs and Export Control). This can also include the central ventilation unit (when combined with air-to-water or brine-to-water heat pumps), as well as all other components (labor costs, control units) required to meet the energy efficiency standards.

It’s best to find a skilled trade company with experience in this area who can calculate the different options for you.

tomtom79 schrieb:

How long have you been living there and do you really have a heat pump? I think this heat pump is not running optimally.

In this case, it’s gas plus solar. The standard temperature in winter is about 21°C (70°F); if we know someone will shower the next morning, we just turn it up a bit so it reaches 22/23°C (72/73°F). As I mentioned, this approach doesn’t really make sense if you keep turning it up and down all the time. The temperature you want to maintain “constantly” in the bathroom should be calculated from the start.

Specki schrieb:

Air-to-water heat pump: 100%
Air-to-air heat pump: 200-300%
Ground-source heat pump: 75%

And now compare the installation costs and operating lifetimes.

Air-to-air heat pump up to around 10,000-15,000 euros

Air-to-water heat pump with underfloor heating and controlled ventilation about 20,000-25,000 euros

Ground-source heat pump with controlled ventilation and underfloor heating 25,000-30,000 euros?

Is that roughly correct?

Specki schrieb:

What this also shows is that the smaller the overall energy consumption, the less impact the chosen heat pump has. Therefore, an air-to-air heat pump (if at all) only becomes interesting when the total energy demand for heating is very low (passive house).

That is why I find it all the more remarkable that major prefabricated house manufacturers like Bien-Zenker, Weberhaus, Streif Haus, Schwörerhaus, and others actively offer customers an air-to-air heat pump. And this, even though none of them typically build passive houses as standard. Basically, the uninformed prospective buyers are clearly being misled here (lower initial heating system costs = easier sales; the subsequent energy costs are not a concern for the prefab house manufacturers).

Ultimately, this discussion has further convinced me to choose a ground-source heat pump...

DaSch17 schrieb:

Bien-Zenker, Weberhaus, Streif Haus, Schwörerhaus, etc. actively offer customers an air-to-air heat pump.

Well, anyone who orders an air-to-air heat pump from Weberhaus and similar companies basically gets a house with a primary energy demand close to that of a passive house.

tomtom79 schrieb:

And now compare the manufacturing costs and service life.

Air-to-air heat pump around 10,000–15,000 euros?

Air-to-water heat pump with underfloor heating and controlled residential ventilation about 20,000–25,000 euros

Ground-source heat pump with controlled residential ventilation and underfloor heating 25,000–30,000 euros?

Is that roughly correct?

I would rather estimate it like this (for KFW 55 standard, 185 m² (1990 sq ft) living space) – including fully operational installation –:

1.) Air-to-air heat pump: 20,000 to 25,000 euros
2.) Air-to-water heat pump including underfloor heating and controlled residential ventilation: 35,000 to 40,000 euros
3.) Ground-source heat pump including underfloor heating, controlled residential ventilation, and drilling: 45,000 to 50,000 euros

tomtom79 schrieb:

Now let's compare the manufacturing costs and the payback period.

Air-to-air heat pump around 10,000–15,000 euros?

Air-to-water heat pump with underfloor heating and mechanical ventilation with heat recovery around 20,000–25,000 euros

Ground-source heat pump with mechanical ventilation with heat recovery and underfloor heating 25,000–30,000 euros?

Is that roughly correct?

I can't really comment on air-to-air heat pumps.

For air-to-water heat pumps with underfloor heating and mechanical ventilation with heat recovery, I think those figures are a bit low. Of course, it depends on the region, square meters, and the heat pump model itself.
Mechanical ventilation with heat recovery costs me about 13,000 euros. Air-to-water heat pump with underfloor heating for 140 m² (1,507 ft²) plus heated basement around 27,000 euros.

Ground-source heat pump including the heat exchanger? Meaning horizontal trench collector or borehole? I also find the estimate including mechanical ventilation with heat recovery to be clearly too low.