BAFA innovation funding air heat pump

Why no buffer? I'm just thinking about whether I should retrofit one to my Stiebel Eltron LWZ 504 to better use the SG Ready function and "store away" the heat. Are there any disadvantages besides the heat loss (which stays in the house anyway) that I am overlooking?

We operate the identical THZ 504, and honestly, what savings are you expecting? Our heating costs are around €60-70 per month. Just an ISG to better utilize photovoltaics costs a good €450. How much can really be saved? €10-20? In another forum, people even estimated more like €5-10 per month. A buffer with the necessary technology is not free either. It will take a long time before it pays off.

No, that would be (if the assumptions are correct, which I cannot and do not want to judge) roundabout 11.9%. You must not add percentages.

I know that Since the 2.5% are only a rough guideline anyway, it is approximately okay at first approximation. The efficiency loss depends on one hand on the heat pump and on the other hand on the temperature range. Basically, for each heat pump, the respective curve would have to be evaluated separately. Then you could have temperature ranges with a 3% slope and temperature ranges with only a 1.5% slope. The 2.5% is an average empirical value that usually fits quite well. Whether it is then only 2% or a full 3% in reality is not particularly relevant. That is why it is also okay to add the 2.5%. You can easily calculate that in your head. 0.975^5 = (100% - 11.9%) I still can’t really do that in my head. Regards Nika