3.9-1=2.9... another step towards parity. And now the costs for maintenance and filters... let's drop it. The calculation is tight (additional investment costs not considered).
I don't like repeating myself. Wait, actually I do... So here is the calculation ONCE AGAIN:
Filter costs for 4 filters each of F7 and G4, if you buy an empty frame and the filter separately: 25 EUR per year (quarterly filter replacement). I took the first offer on Amazon each time; there may be cheaper filters.
A controlled residential ventilation system has an annual performance factor of about 15 to 20. For 1 kWh of electricity consumption you get 15 to 20 kWh of heat back.
Consumption about 35 watts per hour, so 306 kWh per year. Savings accordingly about 4,599 to 6,132 kWh. That also fits well with the practical experience that with a controlled residential ventilation system you can dimension the heating at least 2 kW smaller (with heat pump).
At a gas price of 4.82 cents as we have, savings are therefore 221.67 to 295.56 EUR per year. Electricity costs 306 kWh x 26.54 cents (rather expensive with us) = 81.21 EUR.
Electricity 80 EUR, filter 25 EUR and financing 150 EUR make 255 EUR or in other words, it pays for itself well at current prices and saves money at future prices. Comfort, time savings, better indoor air, etc., all come free on top.
And with us the controlled residential ventilation system has anyway made solar water heating unnecessary. So we saved about 5,000 EUR here (otherwise at least 3 collectors would be necessary with us).
Not to forget, if you heat with an air-water heat pump, you have to pay significantly more than 4.8 cents per kWh of thermal energy.
We already had the discussion about comfort. It doesn't exist.
Better air, cleaner air, no longer having to ventilate but always being able to ventilate. In winter no longer having to let in ice-cold air while the child is playing. At a party not having to ventilate once per hour, etc... And a lot of time saved day after day after day...
Dust filter... whatever. But allergies are rising rather than falling. Want some Sagrotan?
Allergies are rising, correct. That's why the F7 filter also filters pollen. This relief at least for the 8-16 hours at home significantly lowers the risk of an allergy moving up a level for an allergy sufferer. According to current research it is also likely that fine dust and diesel exhaust, which combine with actually harmless pollen and thus enter the body, are partly responsible for allergies. The body recognizes the poison (fine dust, diesel exhaust), but also immediately produces antibodies against the pollen, which it identifies together with it. City dwellers have significantly more allergies than country dwellers. It's not due to the hygiene hypothesis or some magical dirt in the cowshed - this has long been tested. Probably rather chronic exposure of city dwellers to the above-mentioned substances (diesel, fine dust, etc.). Not to mention that it is proven that fine dust exposure leads to arteriosclerosis and cancer. That doesn't mean I want to completely shield myself here. But if I have better air 8-16 hours a day, that suits me fine. Especially since it is FREE.
And also a house without controlled residential ventilation doesn't necessarily mold. So mold protection... whatever. But I have that without controlled residential ventilation as well. So also not a final argument.
And a smoker doesn't necessarily die from smoking. You are a RISK controller. Should I explain your profession to you? Of course the RISK of mold in a non-controlled residential ventilation house is significantly higher than in a controlled residential ventilation house. Still, controlled residential ventilation houses can mold and non-controlled residential ventilation houses can remain mold-free. Similarly, there are lifelong non-smokers without radon exposure who get lung cancer in their 40s and smokers who never get lung cancer.
This is getting too far here. But self-consumption does not make a photovoltaic system wealthy for the owner. It just barely pays for itself and doesn't save a cent. Controlled residential ventilation or not. I have a pool in the garden... I don't save a cent from photovoltaics. If the photovoltaic system survives 10 years I slowly reach the point where I start saving.
And the controlled residential ventilation system makes the photovoltaic system more profitable through base load. Just like that. Whether photovoltaics pay for themselves or not, dear Mr. Controller, is completely irrelevant for this consideration. These are "sunk costs." But if the photovoltaics are there anyway, they become more profitable or less unprofitable through controlled residential ventilation. Depending on the case.
But these are all just side issues. What matters is that the controlled residential ventilation system pays for itself and in some cases is even profitable. Also important is that all other features of controlled residential ventilation come free on top. Whether it's better air in the city, less need to ventilate everywhere or lower pollen exposure for allergy sufferers. Whether it's lower mold risk or higher resale value. All a gift on top of the controlled residential ventilation that pays for itself anyway. Or whether you save 5,000 EUR on an expensive and maintenance-prone solar water heater - as in our case. Here all of that is a freebie on top of a freebie.