ᐅ Recommendation: Air-to-Water Heat Pump versus Local District Heating Network for KFW40 New Construction

Since you are already gathering information, I’m sure you won’t be satisfied with the offered behemoth. There are certainly options smaller than 4 kW minimum capacity that should be installed.
If it doesn’t operate continuously at 8°C (46°F), that’s not really a problem, but below that temperature, it should eventually run continuously. Achieving this with a minimum of 4 kW will only be possible at significantly lower temperatures below freezing. Large heat pumps often also require a higher flow rate, which the heat sink must be able to provide in the first place.

Mark_xx schrieb:

There was a peak output of 5 kW. This supports the statement that the 2-8 kW version is more than enough.

This supports the statement that the 8 kW version is about 40% too large. Even including domestic hot water, 5 kW will be sufficient on 99% of the days. And for those rare cases, the heat pumps have an integrated 3-5 kW electric heating element for additional heating. Using it for two hours per year is more cost-effective than running an oversized heat pump all year round. It is important not only to consider the peak demand but especially the minimum load (as you have already recognized). However, Viessmann offers no alternative below 2.1 kW. In general, there are few options below that. Cycling above 5°C (41°F) is acceptable and only avoided in cases with higher heating demand.

Mark_xx schrieb:

Does anyone have an opinion on district heating – if I decide to use it, would you recommend adding a combined storage tank after the transfer station or possibly just a domestic hot water tank? The district heating water enters the transfer station at about 70-80°C (158-176°F).

District heating, regardless of price or monopoly discussions, has the advantage that you don’t need to worry about your heating hydraulics or the spacing of your underfloor heating pipes. If in doubt, simply set the temperature 2-4 degrees higher. There are surely technical connection specifications (TABs) from the provider, which usually specify transfer stations or types. They often include a small buffer to reduce the connected load. Otherwise, only a domestic hot water tank is needed. With district heating, I would check who operates it and what other networks they run, and try to find pricing information. There are municipal or local utility companies that prioritize long-term operational security and moderate pricing as a public service goal, and then there are others. This can also apply to larger operator companies, but usually, the more private the operator is, the less control you have and the more expensive it tends to be for the customer.

Mark_xx schrieb:

Furthermore, he writes that 7 kW is assumed for domestic hot water preparation.

Did he assume that as a heating installer? On what basis? I would question that, but it doesn’t affect the heat pump choice. The minimum load value should be more important.

Mark_xx schrieb:

Even the 2-8 kW version runs inefficiently above 5 degrees, or am I mistaken?

No, you are right; it starts cycling then. But that occurs with any sizing to some extent. The set point should just be as “warm” as possible. Later, in the control system, you can extend cycle intervals by not heating during transitional nights or by setting long hysteresis or blocking times.

@Mark_xx what decision have you made now?

I am currently facing the choice of continuing to operate a 33-year-old oil heating system or, as part of an extension, switching to a heat pump (including photovoltaic) or district heating.
However, I am completely new to this field and have little knowledge.
Therefore, I would at least be interested in your decision and experience.

Hello @batomek,

Your example is different. You can apply for KFW funding if you install a heat pump. Is there underfloor heating?

What is your quote for the district heating?

@hanghaus2023
In most parts of the existing building, there are standard radiators. In a few rooms (hallway, bathroom, kitchen of the parents’ apartment on the ground floor, bathroom in the granny flat), underfloor heating was installed back then. In the new section, which will be added above the garages and connected to the first floor, mainly underfloor heating is planned (so far).

The local heating network will be implemented by a local construction company. However, it seems it will not be handled through the company but privately by the managing director. At least, this is how I understood it.
There are three connection options based on the contracted output. According to the representative, my previous oil consumption of approximately 4000 liters per year corresponds to category M.
S: Up to 25 kW (€14,500 + VAT)
M: Up to 50 kW (€16,500 + VAT)
L: Up to 100 kW (€19,000 + VAT)
- Energy price 7.5 ct/kWh
- Annual basic charge of €35/kW

Local heating sounds very “convenient” at first. However, I am concerned about the risk of arbitrary price increases or the private operator discontinuing their service in the medium term.

Heat pumps were always a mystery to me. Over time, though, I find the technology increasingly interesting the more I understand it. Still, I am somewhat worried because the property is quite large and aging (built in 1993).

@batomek Do you have a condensing boiler? If not, then upgrading to condensing technology is probably the best solution. A photovoltaic system can’t hurt.

4000 liters of heating oil correspond to approximately 40,000 kWh of heating energy. With a heat pump, this would be about 11,000 kWh of electricity consumption. At $0.30 per kWh, that amounts to $3,300 per year. Investment with KfW support is around 20,000 euros.

The current heating oil price should be about 1 euro, which is roughly $1, so €4,000 ($4,000).

With a condensing boiler, the cost would likely be around €3,000 ($3,000). Investment is approximately 10,000–15,000 euros.

District heating is, in my opinion, the most expensive option.

Investment is €16,500 ($16,500). Basic fee of 50 kW * €35 ($35) equals €1,750 ($1,750) per year
About 40,000 kWh * €0.075 ($0.075) equals €3,000 ($3,000)

Altogether, that totals approximately €4,750 ($4,750) per year.

How large is the house?