ᐅ Exhaust Air Heat Pump vs. Ground Source (Brine/Water) Heat Pump in Rental Apartment Buildings

Hi Forum,

First of all: I am aware that questions about energy systems involve countless influencing factors and have been discussed extensively – unfortunately, I haven’t found the right thread that addresses my specific question, so I’m starting a new one:

Situation:
We are planning to build a semi-detached house for rental with about 105–110 m² (1130–1184 sq ft). Two providers are in the final selection, and with them comes the question of energy supply. In any case, a centralized ventilation system will be installed – both house types are suitable for families, but I don’t have detailed information about the potential heating demand.

Provider A: KfW 40 house, 105 m² (1130 sq ft), relies on an exhaust air heat pump (Nibe F730) or, with funding from BAFA, also on a ground-source (brine-to-water) heat pump NIBE 1255-6 with trench collector.
Provider B: KfW 55 house, 111 m² (1194 sq ft), offers a gas boiler plus solar thermal system.

Costs
The purchase cost of the ground-source heat pump is manageable due to subsidies – about 5,000 EUR (approx. 5,500 USD) extra. The gas house option is around 15,000 EUR (approx. 16,500 USD) cheaper overall (otherwise the features are roughly comparable).

Our questions:
- Does anyone have experience with exhaust air heat pumps or ground-source heat pumps in rental properties and tenants, and can share their insights? (general use, tenant handling, reliability, electricity costs)
- Is the extra cost of a ground-source heat pump worth it compared to an exhaust air heat pump due to higher/better heating performance?

So far, we tend slightly more towards gas and solar collectors, but it’s more a gut feeling, as the whole spectrum of heat pumps seems incredibly complex and it feels easier to make mistakes than with gas. Subsidies bring heat pumps closer to gas in cost – but is it worthwhile for rental properties?

Looking forward to the discussion.

Best regards

schlckr7 schrieb:

Is the additional cost of a ground-source heat pump worth it compared to an air-to-water heat pump due to higher or better heating performance?

No, when renting, choose the best cost-performance ratio. That would be gas heating. Tenants don’t care how they heat their home – it just needs to be warm. And an extra $10 on heating costs won’t attract any tenants.

I would sign off on that as well – thanks to the subsidy, the technology now comes within a few thousand euros of traditional gas solutions, which puts price and performance into perspective.

I am a bit hesitant about using this technology in a rental property, due to the proper system settings and high electricity costs – on the other hand, the already established gas option feels like a more reliable choice for us. But maybe I’m just cautious and (still) not well informed.

Thank you for your contribution.

schlckr7 schrieb:

correct system settings, lower electricity costs

... tenants end up paying 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. It can only cause problems. You can search the forum here. If you find one positive review, there will be 20 negative experiences against it.

For rental apartments, I would generally prefer gas, unless you cannot meet the KfW subsidy limits with it. And why not use a standard 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°C (140°F) in the hot water storage tank? This might not yet apply for a semi-detached house. If it does, then gas would be preferable.

Ok, provider A says they only offer alternative energy sources – so no gas. Hmm, that helps with the decision.