Air-water heat pump with solar thermal and fireplace? Cost/benefit/meaning

Hello everyone,

First of all, a few bullet points:

we want to build a single-family house with 121 sqm living space in summer. Ground floor and upper floor, 2 adults + 2 children.

Roof facing south.

Ytong (30 cm) will be used, windows with triple glazing. A underfloor heating system is to be installed.

We live in Hesse, Rhein-Main area.

An air-to-water heat pump will be installed, as we have no gas and do not want to place any tanks for gas/oil/pellets in the house or garden (buried or not).

We would also like a fireplace, for coziness and because we can get wood almost free of charge. Solar thermal is also on the list, the question is only whether it makes sense and if only for water or also for heating.

The following offer is already available to us:

a Nibe air-to-water heat pump split with building heating load up to 7 kW, volume buffer storage 270l with additional buffer storage 100l including Pedotherm underfloor heating.
For solar, 4 sqm – 2 collectors and a buffer storage with 230l volume would be added.
The extra charge for solar is about €4000.

For connecting a water-guided fireplace, for pipes, pump, return lift, drainage safety about €3000 is charged.
I am now calculating approximately €3500 for a fireplace with chimney (outside).
So it would be over €10,000 extra for a fireplace and solar on top of the air-to-water heat pump.

Regarding the questions:
The buffer storage seems very small for the project, is that so?

What makes sense for the heating system, it should amortize as well as possible; with the fireplace desire it probably won’t work, but well, fireplace is also a luxury and would be accepted even if it doesn’t turn into a money pit.

Just an air-to-water heat pump worries me during the cold season, because of electricity costs and 7 kW building heating load seems low to me (but I have no knowledge about it). A friend has an air-to-air heat pump and the electricity costs there are currently through the roof.

What makes sense, what else should I consider, what have I not thought about or should think about?

What do you think of Nibe?

Regards

Max

Hi,

I'm afraid solar thermal won't pay off - not even over 10-15 years. In winter, almost nothing comes from above, and in summer, the air-water heat pump isn't exactly weak either.
The fireplace only pays off if you don't pay for the wood and have enough wood available. Purely for coziness, it was too expensive for us - we would have had to build somewhat larger overall to accommodate it, the control system would have become complex, and experience shows it wouldn't be used that often anyway.

As for the electricity costs with an air-water heat pump - I wouldn't install an air-water heat pump on the Zugspitze or the Brocken, but with the moderate temperatures near the Main, it looks a bit different. Then it basically still depends on insulation and heat demand - the additional costs for the gas connection (30m to the street, 50m to the next gas line) at least spoke in favor of the air-water heat pump for us.

Regards
I.

After longer consideration, we have also decided against solar thermal energy; the €4000 is better invested elsewhere in the construction project.

I am still not sure about the layout of the buffer storage regarding the chimney, but since solar is no longer an option, there might be a better alternative with the existing air-water heat pump and the offer already available.

For the connection of a water-based fireplace, for pipes, pump, return flow lift, drain safety, nearly €3000 is charged. I am now calculating about €3500 for a fireplace with a chimney (outside).

You need a larger buffer storage for the fireplace, the control system, maintenance, etc. How much more electricity do you need in winter for the air-water heat pump? €20-50? You have to / can heat for a long time until the wood pays off. For €3,500 fireplace + outdoor chimney it gets tight. If a controlled residential ventilation is added and you need a certified fireplace, it won’t work.

only up to 50.- € in heating costs saved, what do you mean, per month or per year, I'd rather ask stupidly.

I can't calculate it exactly, but if I now assume an average of 35€/ per month savings and 5 months per year, then it is 175,- € per year, so the connection to the heating would be paid off again after about 17 years. Without including wood costs etc.

Feel free to wake me up mercilessly

In my opinion, you will not be able to cover the costs set for the stove and external duct. I would budget at least double, preferably more, since you plan to use the stove often. A decent continuous-burning stove costs a pretty penny. Have you ever been to a stove builder for advice?

Underfloor heating is sluggish compared to radiators. A water-fed stove mainly heats the heating system and is supposed to relieve it. However, it heats the rooms less and costs significantly more to purchase than an air-independent stove without a water jacket. This would heat the rooms. Probably so much that you'll have to throw the windows wide open during the heating period because it gets too warm.

Unfortunately, I cannot tell you if the offered air-water heat pump is sufficient.
We will be heating with gas. Our trench is about 60 m. The costs for the gas house connection amount to just under €2,000. We had the trench and laying of empty conduits carried out by the local civil engineer together with the supply and disposal pipes. Everything is negotiable with the utility providers. The house had to be connected anyway.

How is it with you regarding Telekom and water/sewage? If everything had to take the same route as the gas... Unless gas is absolutely not available.