ᐅ Is a brine-to-water heat pump still worthwhile for a KfW 40+ energy standard building?

RotorMotor schrieb:

So, that already gives you an answer. ;-)
But there are other reasons as well.
For example, my impression is that surface collectors are only offered by a few companies.
DIY is also not an option for everyone.
In principle, however, it is a good option that should be considered more often.

Wait, so no additional cost or only a small extra cost?
How was the collector installed in your case?

For us, no extra cost. Usually paid in advance. About 50% of the cost of the deep drilling.

Starting in calendar week 2 of 2022, the groundwork for the collectors will begin. The collectors will be stacked on top of each other. As far as I remember, their dimensions are 25 meters (82 feet) in length by 4 meters (13 feet) in width. They are buried about 80 cm (31 inches) deep. A drainage system is installed above to improve efficiency. The pump is the latest model from Bosch (Compress 7800i LMW). There is also a temperature control system.

RotorMotor schrieb:

There are hardly any reasons why electricity should become significantly more expensive.
Electricity from wind or solar currently costs only about 3-8 cents/kWh to produce.

That’s exactly what I think as well. Generation is becoming cheaper, storage too (and at the same time more efficient).
The reason it will be more expensive for now lies in the structure of the Renewable Energy Act surcharge and the massive exemptions from it (the surcharge is simply charged to too few consumers and is therefore significantly too high).
In the long term, energy will become cheaper again. This transition period is just costly.
(Please do not generalize from energy to other resources – some things are simply becoming scarce and expensive…)

For aesthetic reasons, we chose a ground-source heat pump… but I guess you’re not supposed to run the numbers 😳

Even though the “heat” coefficient of performance (COP) of a ground-source heat pump clearly has an advantage in very cold temperatures due to the system design, a relatively large amount of electricity is needed for pumps and other components in the overall system – which in turn affects the overall COP, making an air-source heat pump more favorable again. The ratio of auxiliary power to heating power becomes more unfavorable the lower the heating/domestic hot water demand… and two units of 95m² (1,023 sq ft) KfW40-standard homes will certainly have a very low demand (is there already a calculation?). And then there is the question of what actually generates the greatest heating need averaged over the year: a few days at -10°C (14°F) outdoor temperature, or the several months around 0°C (32°F)?

The additional cost of a ground-source heat pump would definitely make more economic sense with careful planning and installation, combined with as large a solar photovoltaic system as possible. Unless, of course, you share our allergy to outdoor units 😉

Tom1978 schrieb:

The calculation is very simplified. You assume that electricity costs remain constant. How likely is that? The higher the electricity costs, the greater the savings...

Of course, it is simplified. But the difference won’t increase significantly since both heat pumps run on electricity. Whether I recoup the additional investment in 35 years or 60 years doesn’t really matter in the end.
The larger the house and the smaller the extra cost—or if a horizontal ground collector is possible—the more attractive the brine-to-water heat pump becomes.

But in a typical house with an extra cost of €5,000, you’re already far from an economically sensible decision.

As I said, I have already had a brine-to-water heat pump with deep drilling. No outdoor unit and a strong selling point when we sold the place. It was also a 300 m² (3,230 ft²) house to heat...

Hangman schrieb:

We have a ground-source heat pump for aesthetic reasons... I guess you’re not supposed to calculate the costs 😳

That calls for a laughing emoji. Turning a blind eye to cost-effectiveness is a common human trait.

• Have you ever eaten out?
• Bought an item of clothing that serves more than just the purpose of warming and covering? (Or shoes...)
• Purchased the most economical vehicle?
• Taken a vacation?
• Given someone a gift?

Enjoy the absence of the outdoor unit—I think decisions like these are practical in everyday life, at least in a private context.

Very interesting. I think that if we decide on a ground source heat pump, then horizontal trench collectors (or possibly baskets, although I haven’t found any useful information about those yet) could be an option. We could do the excavation work ourselves, which would already be considerably cheaper than drilling. Unfortunately, there is no precise calculation of the heating load or domestic hot water load yet.