That’s exactly what I don’t like, and that’s why I sent my detailed comment to "Kill your darling". Here, someone is apparently rock-solid convinced of their product and rubs everyone the wrong way who questions it and raises concerns.
So, it annoys me so much here that I actually fired up Excel.
The result over typical financing periods, which at the same time represent the target lifespan of the heat pump, does not surprise me at all. I see all my theses and warnings about the system confirmed. If anyone asks me, I would not recommend the window heating system to anyone.
Since the topic of sustainability was also mentioned, I quickly checked that roughly again. CO2e for German steel assumed at about 2.5kg, PE floor pipes 17x2 with 2kg CO2e. Production overhead calculated at a flat 25%.
By the way, I am also an engineer and at work I occasionally deal with determining CO2 footprints, so with my many years of expertise I assert that these are good reference values.
The CO2e of the German grid mix is of course problematic. Before the war, there were ambitious goals that I now strongly doubt, especially since there are still East German brown coal power plants running. I simply assume our government will reach the <25% compared to 1990 target only 10 years later, in 2040.
So, I simply calculated the electricity. Unfortunately, I have very serious doubts that it will go so well!
The very sobering result with the input parameters I chose is that over the 15-year service life, 16 tons of CO2 including production costs and operation are emitted more. The longer we keep this going, the worse the CO2 balance of the window pane heating becomes.
Significantly worse balance of the window heating compared to the heat pump, naturally due to the efficiency.
And now please don’t argue with the free photovoltaics. I already disproved that argument with the first calculation. Over the financing period, there are no significant differences from a cost perspective, so photovoltaics must be considered on top in both cases. It should also be noted that from November to February, 63% of the day the sun doesn’t send a single photon directly onto the photovoltaic surfaces. So 2/3 is heated with the grid mix and the last 1/3 is usually so sun-obscured that even a 15 kWp south-facing photovoltaic system cannot cover the base consumption of the house without heating. A few sunny days make up for it again, as long as there is no snow on the modules.
Photovoltaics and heating have to be strictly separated for the analysis. Therefore, in my opinion, it is highly disingenuous that this system is advertised with free photovoltaics.
Since I haven’t had enough yet, I’m going to look at my heating load calculation again right away and raise some critical questions regarding heating the basement and my bathrooms, where I cannot install large window areas.