ᐅ Is the additional cost of an air-to-water heat pump compared to gas justified?

Hello everyone,

I could use your advice on choosing a heating system. We (2 adults, 4 children) are currently in talks with a general contractor (GC) about a house, and so far it sounds pretty good. The scope of work is acceptable. We are not aiming for a specific KfW energy standard but expect to land somewhere between 70 and 55. The heating load calculation is not finished yet since the contract is not signed.

The GC’s standard offer includes the following:
Gas heating: Vaillant auroCOMPACT VSC S 206/4-5 190 condensing compact unit
Rated at 20 kW (wow, why?)
Includes a 190 L (50 gallons) hot water storage tank, plus 2.5 m² (27 ft²) of solar thermal collectors as a package.

Alternatively, he offers an air-to-water heat pump as a substitute for the gas heating and solar thermal system:
Thermia iTec Plus with 9 kW output, cooling function, and a 300 L (79 gallons) hot water storage tank alongside.

I would actually prefer to go with the heat pump, but:

The additional cost for the heat pump solution is a hefty €8,100. For that, we wouldn't need a gas connection...
Maybe I’m mistaken or the math doesn’t add up, but does it really pay off to choose the heat pump?
Even if you achieve a COP of 3.5 or 4, the extra cost of €8,100 minus €2,500 for the gas connection = €5,600 would only pay off very, very late.
At €0.30 per kWh electricity and 10,000 kWh annual consumption with a COP of 4, the cost would be €750. At a gas price of €0.10, the cost would be €1,000. So the difference is €250 per year, meaning the extra cost (ignoring the solar thermal system) would only amortize after 22 years.

Is that correct, or am I missing something / making an error in the calculation? Given the additional cost, I am leaning towards gas, possibly with an extra hot water storage tank.

Thanks and best regards
SoL

Addendum: Even at a stable price of 13 cents per kilowatt-hour as it is now, the payback period would still be more than 10 years.
I signed a contract for 10 cents per kilowatt-hour in January, fixed for 2 years for the existing house...

You are right. If you don’t specifically need to achieve KFW 55 or lower, which wouldn’t really make sense anyway, the heat pump is still too expensive at the moment. It should also be noted that it tends to require more maintenance.

Nordlys schrieb:

You are right. If you don't specifically need KfW 55 or lower, which wouldn’t really make sense anyway, heat pumps are still too expensive at the moment. It must also be said that they are more prone to maintenance issues.

Sorry Karsten, but that’s simply not true. Once installed and properly configured, they require virtually no maintenance.

Regarding the question: No, the price is NOT justified. Not at all. And the gas heater is also completely oversized. What difference does it make if you remove the heat generator from the scope of work?
Make sure to include a room-by-room heat load calculation, including the design of the underfloor heating based on this heat load calculation.

Joedreck schrieb:

Regarding the question: No, the price is NOT justified. Not at all. And the gas heating system is also completely oversized. What difference would it make if you have the heat generator removed from the scope of work?
Be sure to include a room-by-room heat load calculation including the design of the underfloor heating based on this heat load calculation.

Is it sufficient to mention that the calculation is according to DIN EN 12831? Excerpt from the scope of work:

All rooms on the ground floor and attic/upper floor will be fitted with underfloor heating, providing a comfortable and cozy warmth in your home. The warm water underfloor heating system consists of heating loops on carrier plates with the necessary insulation, and the pipes are made of cross-linked polyethylene (PEX). The length of the individual heating circuits and the spacing of the pipes are designed according to DIN 4701, the Energy Saving Regulation proof, and the heat load determination according to DIN EN 12831. The underfloor heating system is designed so that it can be connected to a heating system with low supply temperatures, enabling operation or conversion to the use of renewable heating systems.

Removing it would reduce the "gross construction costs" – how much exactly, I would need to inquire, but I suspect it would be a small amount.

Thank you
SoL

The additional cost for the heat pump seems excessive. This could imply that the general contractor (GC) is not interested in installing it. If you can clarify this with the GC or manage the contract yourself, I would generally recommend going with the heat pump. Otherwise, you need to consider whether you want to push the GC to do something they are reluctant to do... at worst, because they are not skilled at it.

What about the cooling function? Do you need or want it? If not, can it be excluded from the calculation?