Vestaxx window heating - experiences?

One more brief remark about the numbers, which are again not completely accurate:
The calculation is flawed in that you shouldn't use room temperature, but rather the surface temperature of the heating element. And that is about 32 degrees versus 8 degrees = 24 Kelvin for underfloor heating, and 43 degrees versus -5 degrees = 48 degrees for window heating, whereby with an outdoor temperature of -5 degrees you should probably assume 50 degrees.
That shifts the result a bit again.

I would also like to add my two cents regarding the system technology.

To avoid having to keep additional system technology with window heating, only instantaneous water heaters remain.
If bathrooms are located on different floors, they should be electrically interlocked.
Well, it’s not a big deal, but it should be considered.
Electric instantaneous water heaters are no longer worthwhile with high water volumes; I wouldn’t necessarily want to equip a household of 4 people with long-term showerers with one.

No matter how cold it is outside, in Germany heat pumps achieve at least a COP of 1.8 on 330 days a year.
Since a heat pump becomes less efficient the higher the heating water temperature is, it would be smart to operate the heat pump continuously with a flow temperature of 35 degrees. Through the buffer tank with primary/secondary circuit, the fresh water is then warmed in flow-through mode to exactly 35 degrees and, if necessary, then supplied to the instantaneous water heater, which realizes the marginal temperature increase to 45 degrees.
This way I keep the instantaneous water heater’s power demand within limits, have no problems with legionella, and do not have to maintain a temperature of 60 degrees as with a domestic hot water storage tank.

Why do I explain this so extensively? Because with a heat pump these components are already available through the heating technology. The investment in a domestic hot water heat pump combined with window heating disproportionately increases the primary costs. And in winter, if it is supposed to produce hot water alone, it is no longer efficient.

I would really appreciate a sober, mathematically correct consideration including all side effects, in order to be able to formulate a real decision aid for the technically knowledgeable homebuyer.

There are certainly arguments that could make this technology appealing.
But then please also comprehensible and without false promises.
I only say: comfort, heat veil, lack of inertia, ease of maintenance, system technology, retrofittability, water feel, delivery time, manufacturing process etc.
Consumption is simply not one of them.
But there’s always something.

Regards, Christian

A heat pump also offers the advantage of a cooling function (of course depending on the type of heat pump). Likewise, with a water-based distribution system, I can relatively easily change the generation system.

I tend to find it good that the entire house or building technology is seen as a system and not each component viewed individually. Burning high-quality electricity 1-to-1 for heating, I view skeptically. Reducing it solely to economic efficiency is also not the best approach in today's times.

Out of curiosity, where are the advantages compared to other direct electric heating systems? Infrared panels, built-in electric heaters... Or even more interesting would be the comparison with an air conditioning unit. It only costs me a few thousand anyway and is at least an LL heat pump.

Likewise, I can relatively easily change the generation system with a water-based distribution system.

And that was the decisive point for me, to always have underfloor heating included in the offer despite air heaters being often offered gladly. In this case, by the way, we then not only have a heating element in the ventilation that can certainly be replaced otherwise, but a special system that apparently only comes from one manufacturer. Whether it will still exist in 10, 20, 30 years...?

By the way, I stick to the view that if you follow the line of argument with the low investment, then just buy electric fan heaters and every week open a nice bottle of wine with your dream woman from the money saved. Probably provides more comfort than a heating window ;)

With the resulting responsibilities, you are far behind when it comes to ongoing costs. Better to go with a window heater, which is significantly cheaper over time.

With the resulting responsibilities, you are quite far behind when it comes to ongoing costs.
Better to go for a window heater after all, it's significantly cheaper over time.

Colleague from management with a locked profile? :)

Yes, I know from multiple discussions that it is really hard for some to understand, so here it is again and gladly once more in short.

Yes – a heat pump has an annual performance factor of say 3 or even 4 (without losses) and our window heating including losses to the outside of 0.95. However, whoever stops thinking or calculating at that point makes the crucial mistake.

What drives the user – especially at this time – is -> What will I pay for the kWh of energy in the next 20 years.
Please consider the energy flows into a house that NEED TO BE PAID FOR!

And yes again – of course, a direct electric heating system uses about 3-4 times as much as a heat pump – yes and yes again!
But the heat pump only has to cover the heating and hot water demand and needs electrical energy for that.
In addition, the house still needs household electricity, but unfortunately, the heat pump does not provide anything for that at all.

So – now let’s look at another system – which is AVAILABLE FOR THE SAME PRICE as a heat pump.

The homeowner gets a window heating system, a hot water heat pump, a large photovoltaic system, and possibly a battery for the same cost!!! This way, they generate more energy annually on balance than they need -> plus-energy house. In winter, they have to buy electricity – in summer, they feed surplus electricity into the grid and get paid for it. From that, they can buy electricity again.

In the complete balance, you pay much less annually than with a water-based system (heat pump or pellet heating).
This is called full cost accounting.

If you buy a car for €40,000, for example, and brag that it uses only 1/4 the fuel of another car, you ignore that the other car costs only 1/4 as well and that you can buy a "gas station" with the remaining €30,000.

And now once more – but this time for the last time -> It is hard for some to comprehend why our system has (still) not prevailed, but since the turning point, people have calculated what they pay and consume. Everyone can tell me at the moment what they have to pay for oil, gas, or electricity. Before February 2022, that was very very little. And every end customer to whom I calculate the full costs understands me.

I am slowly also meeting approving people among energy consultants. But there has not been one yet who could calculate the opposite for me.

You’re welcome to make this public here. Come on, just do it!