Vestaxx window heating - experiences?

A small addendum because I just can’t leave it as it is:

COP of 3.5 -> I accept that. That is the efficiency of the air-water heat pump under fixed conditions.
When different temperatures come into play over the heating period, one speaks of the lower annual performance factor (Jahresarbeitszahl).
Both indicators are measured at the heat pump outlet. What is NOT included in this are the distribution losses.

To fairly compare the heat pump with a direct electric heating system, the system efficiency must be used.
This was only confirmed to me last week by Prof. Henning from Fraunhofer Freiburg on the occasion of an association meeting of the Federal Association of Energy Consultants in Fulda. There are also economic findings related to this, which I have mentioned here before.

What bothers me every time is that – by whoever – COP or annual performance factor are given and the customer is given the good feeling that here from one kWh of electricity multiple times the amount of energy in the form of heat is obtained. But the customer can never verify the factor – without enormous metrological effort. You just have to look at the flow temperature of the heat pump in relation to the temperature at the interface of the underfloor heating to the human and admit that energy is “lost” on the way from the heat pump to the human.

Only he can never verify the factor - without enormous metrological effort.

Well, there are quite a few people in this forum alone who have built with an air-to-water heat pump + underfloor heating, and they can verify this very reliably based on their consumption figures. This is not just blind theory; the systems are in use.
In our new build with an air-to-water heat pump (and photovoltaics! Shock!) we had about 2350 kWh consumption in one year. Of that, 14% came from the photovoltaics and 86% from the grid. At that time, the kWh still cost 28ct here, so even without photovoltaics we would have had costs of 2350 x 28ct = €658 per year.
That is just under €54 per month. With that, we kept 153 m² warm (24°C room temperature, we like it cozy) and hot water & ventilation were also included.

Relatively easy with a heat quantity meter. Normally, there is already a measurement installed in the heat pump, electricity consumption is also included. Otherwise, you can install a heat quantity meter directly after the heat pump for monitoring and then, for example, add something before the underfloor heating distributors. If the heat pump is located in the conditioned area, then there are practically no distribution losses anymore (it also heats the house for me). An annual performance factor of >3.5 for an air-water heat pump is no longer uncommon in new buildings. Proper system planning and execution are assumed (there is certainly still plenty of potential here and with an electric direct heating system, you can make few mistakes). When considering the annual performance factor, one must not underestimate the domestic hot water preparation from spring to autumn. The air-water heat pump achieves very high values there.

Well, there are quite a few people in this forum alone who have built with an air-water heat pump + underfloor heating, and they can verify that very reliably based on their consumption figures. This is not just theory; the systems are in use. In our new build with an air-water heat pump (and photovoltaics! Shock!) we had about 2350 kWh consumption in one year. Of that, 14% came from the photovoltaics and 86% from the grid. At that time, the kWh cost 28 cents for us, so even without photovoltaics we would have had costs of 2350 x 28 ct = €658 per year. That amounts to about €54 per month. With that, we kept 153 m² warm (24°C room temperature, we like it cozy) and hot water & ventilation were also included.

Yes, all correct – but the people can only see the consumption figures, not what the house really consumed net. Or in other words, no one can really say how much heat actually reached the people directly. At best, you can roughly compare it to the heating demand calculated by the energy consultant, but that is not representative either, because weather conditions and heating behavior are still variables -> that’s why everyone is happy about relatively low annual or monthly heating costs as you described. In the full cost accounting (refer to the webinar on our homepage at this point – it explains this in detail) it looks completely different.

The heat pump industry is leading customers – in my very personal opinion! – nicely by the nose ring through the ring, and they don’t even notice it.

Yes, that's all correct – only people can merely see the consumption figures, but not what the house actually consumed net.

Huh? What do you mean by what the house consumed "net"?

Or in other words, no one can really say how much heat actually reached the person directly.

A thermometer can tell that fairly well.

At most, make an approximate comparison to the heating demand calculated by the energy consultant,

Who cares? What ultimately counts is what it costs me monetarily to have a temperature in the house at which I feel comfortable.

but even that is not representative, because weather and heating behavior are still variables involved ->

You can cut out the variables since neither weather nor heating behavior should change depending on the heating system. I don’t suddenly find 20°C better than 24°C just because I have a different type of heating. And I won’t get a colder winter because of that either.

therefore everyone is happy about fairly low annual or monthly heating costs as you have shown. In the full cost calculation (refer here to the webinar on our homepage – it explains this in detail) it looks completely different.

Like what? What are your promised figures in the full cost comparison based on my example?

The heat pump industry is leading customers – in my personal opinion! – nicely by the nose ring through the arena and they don’t realize it.

And you’re trying to spin a story here and THINK we don’t notice.

It's relatively easy with a heat meter. Normally, there is already a measurement installed in the heat pump, including power consumption. Otherwise, you can install a heat meter directly after the heat pump for monitoring and then, for example, add something before the underfloor heating distributors. If the heat pump is located in the conditioned area, then there are no real distribution losses anymore (it also heats the house for me). An annual performance factor of >3.5 with an air-water heat pump is no longer a rarity in new buildings. Provided proper system design and execution (there is certainly still enough potential here, and you can make few mistakes with an electric direct heating). One must not underestimate the hot water preparation from spring to autumn when considering the annual performance factor. The air-water heat pump achieves very high values there.

Very good points, all of which I agree with, except for the note that it can be checked with a simple heat meter. Where that is located – not at the distributor either – we do not want to measure, but at the heat transfer point to the person. Measuring there is extremely difficult. And also the objection: the waste heat remains in the house ... unfortunately, that is not quite correct. The underfloor heating has a huge radiator beneath it -> the ground with, let's say, a continuous 12 degrees Celsius. Delta T to the supply temperature of, let's say, simply 28 degrees Celsius -> results in a delta T of 16 Kelvin. In connection with the floor area and the U-value of the floor to the ground, you can calculate the continuous loss power to the ground. And that is often even higher than the losses through the window glass.