Electric surface heating (Thermoheld) in KFW 40 bungalow with 80 sqm

First, one should clarify the standard outdoor temperature. I assume -12°C, and that is not ideal for the air-to-air heat pump.

Yes, the efficiency is not outstanding. But given the size of the house and its efficiency, that is not tragic. The additional investment of several tens of thousands of euros for a heat pump with underfloor heating will never pay off.

Interesting, I hadn't thought of an air-to-air heat pump/split air conditioning system before; I always thought it would dry out the air, like air conditioners do when you travel. But presumably building technology has advanced? How do you arrive at the €30–35/m heating costs?

House size combined with KfW 40 will result in somewhere between 1,500 and a maximum of 2,000 kWh electricity consumption. At current electricity prices of about 25 cents per kWh, that's between €375 and a maximum of €500. Photovoltaic yields are not considered. That's why my objection that the heating technology does not have much financial impact. A 20% higher consumption, i.e., €100 per year, adds up to only €2,000 over 20 years (without electricity price increases). That's bearable if the heat pump + underfloor heating perhaps costs €20,000 more than the air-to-air heat pump. You also wrote that the water-based underfloor heating heats up quickly. That is a misconception. Water-based underfloor heating in screed is mega slow. You only notice changes in room temperature after several hours/overnight. At least if you only have a maximum of 30 degrees as the supply temperature in the deepest winter. That is the slowest heating form you can choose. But in a KfW 40 house, you lose only 1 degree overnight if the heating fails.

House size in connection with KfW 40 will somewhere give 1,500 - maximum 2,000 kWh electricity consumption. At current electricity prices of about 25 cents per kWh, that is between €375 and a maximum of €500. Yields from photovoltaics not considered.

Thanks for the calculation details!

I first have to find out what the air-water heat pump and (if possible) air-air heat pump would cost & what energy demand is present.

As I said, the provider normally only installs their own electric surface heaters (see picture) and water-based underfloor heating usually only if district heating is available (due to the low energy demand?).

Their heating system would be included in the price - therefore I have to see if the extra cost is worth it just for the air-to-air heat pump, especially if the system is not much more efficient. Regardless, I unfortunately have no experience with air-to-air heat pumps/split air conditioning units and therefore cannot assess whether I like the system in terms of room air (e.g. dry or draft). I am rather sensitive to both (mucous membranes & eyes). Noise-wise, the infrared/electric panel heating would of course be a plus.

I just had another thought: besides variants A (air-water heat pump) and B (air-air heat pump), also

C (electrical surface heating, included in the price) but larger photovoltaic system:
- 3,000 kWh energy demand in the heating period (2,000 kWh heating energy demand + 1,000 kWh useful energy demand)
- roof area of the house facing south: 58-77 sqm (yields 2,500-3,400 kWh output in the heating period)
- costs according to the house manufacturer for photovoltaic + storage with 11.7 or 15.6 kWp photovoltaic system: €22.5K or €27K respectively

That means, instead of choosing the upgrade to another heating system, I could simply pay the approximately €7K additional cost for the 9.1 kWp system and cover my entire heating energy demand myself, have no problem with possibly dry air/drafts (air-air heat pump?), and not have the noise emission of the air-water heat pump for overall less extra investment.

It is well known that it always makes sense to stay "close" to the manufacturer's standard equipment; everything else is charged expensively because they cannot distribute the planning costs over a large number of customers (modular construction).

A larger photovoltaic system is often a good idea. However, the basic problem remains that the heating usually runs when the sun is not (well) shining. You can also simulate this with pvgis. So even with a large photovoltaic system, a heat pump can still have advantages!

But the fact that the heating usually runs when the sun is not (well) shining remains a basic problem. You can also simulate that with pvgis. So even with large photovoltaic systems, a heat pump can still have advantages!

Thank you for the renewed hint to PVGis, it helped to visually see the low energy generation in winter. According to PVGis, for the period Nov-Feb, an 11.7-15.6 kWp photovoltaic system with 18° tilt should deliver 1,440 - 1,920 kWh at my place. Heating energy demand Nov-Feb KFW 40: approx. 1,400 of the 2,000 kWh, useful energy demand Nov-Feb 500 kWh. That means I need 1,900 energy demand, so I should opt for the 15.7 kWp photovoltaic system + storage (€27k). And after one year, as soon as I have experience values, I could retrofit an air conditioning system (=air-to-air heat pump/split air conditioner?), in case my photovoltaic yield is still not enough for heating + useful energy, right? The good thing is: With this floor plan (see attachment), an air conditioning system would probably suffice to heat the living space + bathroom (open door), I think – and in the bathroom and everywhere else I also have the electric ceiling radiant heating.