Exhaust air heat pump vs. brine/water heat pump in the rental building

Hi Forum,

first off: I am aware that the question about energy types has countless influencing factors and has been discussed a thousand times – but unfortunately I haven't yet found the right thread that addresses my question, so I am opening a new one:

Situation: We are planning to build a semi-detached house for rental with about 105-110 m². Two providers are in the final running and with them also the question of energy supply. In any case, a central ventilation system is to be installed – both house types are suitable for families, but unfortunately I don't know more about the possible heating demand.

Provider A: KFW40 house 105m², swears by exhaust air heat pump (Nibe F730) or, with BAFA subsidy, also a brine/water heat pump from NIBE 1255-6 with trench collector.

Provider B: KFW55 house 111m², offers a gas boiler plus solar system.

Costs Acquisition costs of the brine/water heat pump are "within range" thanks to subsidies – approx. 5k additional expense. The offer for the house type with gas is overall approx. 15k cheaper (otherwise roughly comparable in features).

Our questions:
- Does anyone have ALWP or brine/water heat pump in rental properties and rental and can share their experience? (Generally, tenant handling, susceptibility, electricity costs)
- Are the additional costs of the brine/water heat pump worthwhile compared to ALWP due to higher/better heating performance?

So far, we tend somewhat more towards gas and collectors, but it is more of a gut feeling, as the whole spectrum around heat pumps seems incredibly complex and somehow you can make more "mistakes" than with gas. Subsidies and grants are always bringing heat pumps closer to gas – but is it also worthwhile for rentals?

Looking forward to discussions

Best regards

Are the additional costs of the brine-water heat pump worth it compared to ALWP due to higher/better heating performance?

No, for a rental property choose the best price/performance ratio. Gas offers you that. The tenants do not care at all how they heat - it just has to get warm. And 10€ more or less in heating costs does not interest anyone either, you will not attract tenants with that.

I would sign off like this too - but with the subsidy, the technology comes within a few thousand euros of traditional gas solutions, which puts price/performance into perspective.

I am a bit put off by the technology in a rental property, the correct settings of the system, and high electricity costs - on the other hand, the already established gas is a safer choice for us. But maybe I am just anxious and (still) poorly informed.

Thank you for your contribution.

correct settings of the system, high electricity costs off

... the tenants pay those anyway. So don’t be discouraged by that. But it’s true, gas technology is simpler and cheaper. Exhaust air heat would have been ruled out for me right from the start. That can only lead to problems. You can search here in the forum. If you find a positive assessment, there are 20 negative experiences against it.

For rental apartments, I would tend to prefer gas, unless you do not reach the KfW funding limits with it. And why not a regular air-to-air heat pump instead of the exhaust air heat pump?

Does the size of your project already fall under the regulations for Legionella protection, which require a minimum temperature of 60 degrees in the hot water storage? This might not yet be the case for a semi-detached house. If it is, then gas.

Ok, provider A says he offers nothing but alternative forms of energy - so no gas. Hmm, that helps with the decision