Vestaxx window heating - experiences?

This is quite a blast again. The gentleman doesn't even know that a BWWP and an air-to-water heat pump are basically the same technology.

So an air-to-water heat pump is just as much a refrigerator as a BWWP is a refrigerator.
The maintenance effort is therefore identical.
The only argument cooouuuld be that spare parts for a fully-fledged air-to-water heat pump might be somewhat more expensive because it is sometimes larger and more powerful.

We have all checked this several times and supported it with numbers and sources.
The yield in winter is low. Therefore, it is not sufficient to operate a heating system.

Instead of rambling, making claims, and insulting, a counterstatement would be appropriate.

First, RotorMotor writes that nothing comes from the solar system in winter, then again that the yield is rather low.
And that the yield is not sufficient for heating with direct electric heating, I have also confirmed multiple times.

Here, the same old – partly incorrect – loops are spun again and again. This must be a horror for readers who expect decision-making help here to read these texts.

I cannot convince RotorMotor, and I will not try any further.
That would mean that you would have to admit having chosen the uneconomical system.

We will be successful, and this is reflected in conversations with experts and home-building companies. A lot is happening right now, and you will read and hear from us.

Be happy with your heat pump! ;o)

Why don’t you compare systems that are comparable. If you obviously have a problem with heating cables in the screed (either because of the costs or because of the water), then the comparison object to your window heater is quite classically the air-to-air heat pump. Tried and tested for ages, especially in prefabricated houses when it comes to saving heating costs. Please do a comparison calculation with that, I would really be interested! Since the costs of an air-to-air heat pump are lower, you could optionally calculate both heating types with or without photovoltaics, then you would get something comparable.

What systems are comparable? I am not allowed to compare a window heater (direct electric heating) including BWWP and photovoltaics with a heat pump at the same price! But if there is an air-to-air heat pump on the other side, the comparison is allowed again. What sense does that make? And it is not ME who has problems with heating cables in the screed – I don’t have any – but possibly those who will eventually have a real problem with them.

I have also never argued against an air-to-air heat pump here nor compared it, but explicitly addressed water-based systems. The air-to-air heat pump works with air as a heat carrier, is cheaper than an air-to-water heat pump and therefore has advantages over water-based systems.

One could – and please understand this only hypothetically!!! – also buy two hot air blowers with 2000 W power each for a total of 40 € at the hardware store and heat with them. Nobody does that, but it would be possible in a well-insulated house. The investment for the heat pump would then be a factor of 1000 smaller and plenty of money would remain for a photovoltaic system that generates completely CO2-free electricity.

This is just an example to show that you don’t have to spend 40,000 € on complex, highly engineered technology just to get maybe 2–3,000 kWh/year of heating energy from the air: A truckload of technology for a shot glass of energy. But if that’s what you want … we live in a free country … then by all means.

I will then supplement my calculation with the required maintenance costs and a variant without photovoltaics to have all variants clearly presented together:

150m² with 40kWh/m²a -> 6000kWh/a heating energy demand
10kWp photovoltaic + 5kWh storage -> ~15kWh/day in Nov, Dec, Jan, Feb. With 10kWh for household electricity including hot water, 5kWh/day remain for heating
The costs of the photovoltaic system are not listed in this example, as the system finances itself through feed-in tariffs and savings on household electricity.
Hot water costs are omitted as both systems can provide it with a COP of 4 and thus make no difference; the electricity for hot water is included in the household electricity calculation.
Electricity purchase price 35ct/kWh
Feed-in tariff price: 8.2ct/kWh
Interest 3.5% (current interest for 10-year fixed term)
Electricity price increase 6% (average of the last 20 years)

Vestaxx+Photovoltaic:
Surcharge over normal windows: €10,000
Purchase and installation of BWWP: €5,000
Interest for purchase over 18 years: €5,239
Maintenance BWWP: €200/a
4 [months] * 30 [days] * 5 [kWh/day] = 600 [kWh] from photovoltaic electricity
5400kWh remain to be purchased
Total (average, due to rising electricity prices) 5400*(35+35*1.06^18)/2+600*8.2=€3,691/year
After 18 years that makes: €90,286

Heat pump + Photovoltaic:
Hydraulics: 80€/m²*150m=€12,000
Purchase of air-water heat pump monoblock and installation: €20,000
Interest for purchase over 18 years: €11,176
Maintenance air-water heat pump: €250/a
Electricity demand: 6000/4=1500kWh
900kWh remain to be purchased
Total (average, due to rising electricity prices) 900*(35+35*1.06^18)/2+600*8.2=€656/year
After 18 years that makes: €59,488

Vestaxx without Photovoltaic:
Surcharge over normal windows: €10,000
Purchase and installation of BWWP: €5,000
Interest for purchase over 18 years: €5,239
Maintenance BWWP: €200/a
Total (average, due to rising electricity prices) 6000*(35+35*1.06^18)/2+600*8.2=€3,691/year
After 18 years that makes: €94,558

Heat pump without Photovoltaic:
Hydraulics: 80€/m²*150m=€12,000
Purchase of air-water heat pump monoblock and installation: €20,000
Interest for purchase over 18 years: €11,176
Maintenance air-water heat pump: €250/a
Electricity demand: 6000/4=1500kWh
Total (average, due to rising electricity prices) 1500*(35+35*1.06^18)/2=€1,011/year
After 18 years that makes: €65,878

This results, in this example, in additional costs for Vestaxx of €30,798 compared to the heat pump.
So for 18 years, every month paying €142 more per month without ending up with the underfloor heating at the end of the term!
All the money is gone to the energy supplier and largely converted into CO2.

That was not an answer to my question at all! An air-to-air heat pump is similar and cheaper.

Only a small niche remains for it to make any sense. But it does exist

The niche exists, but it doesn’t fit into marketing. The niche for window heating is – like for infrared, air heating, etc. – a house close to the passive standard that hardly requires any heating. For such a house in the highest price range, I am no longer allowed to argue that the builders cannot afford photovoltaics. The class of builders with little money is certainly more efficiently covered by the Building Energy Act + underfloor heating + Daikin heat pump.

I can't convince RotorMotor and I will not try any further.

That is an understatement, otherwise you couldn't convince anyone either. :)