Assessment of heating concept KfW70

For maximum cost efficiency, one forgoes hot water.

Your statement is theoretically completely correct. Practically speaking, hardly any homeowner can exactly predict how their usage behavior plus the usage behavior of all other "residents" will be. Just consider, one moves in as a couple or with a baby, but in 15 years there is a small group of teenagers, living as five, perhaps with grandma moved in and living as six. The eldest likes to shower under the Rechtsanwältin-Shower-Brausekopf for 30 minutes at a stretch, grandma wants to take a full bath at least once a day, and every third day the mini-swimming-pool is refilled.

The 500-liter tank is not a bad choice, hygienically completely safe, and compared to the six-figure sums involved in house construction, the higher operating costs are absolutely negligible.

No, the user behavior of the future is not known. But you are exaggerating so immensely that you can’t plan anything in the house with it. Most people here know about children/number, and whether there is space for grandma as well. If you factor that in, and think you need that much, and, not entirely unimportant, can afford it, why not. If your case occurs, 500 is too small, if the pool is half full, the storage tank is empty and your grandma has to wait 3 hours until it’s warm enough for her full bath. You can, because a house is already so expensive anyway, quickly buy your eldercare bed and put it in your later bedroom on the ground floor (just to exaggerate as you do). Just take 100 sqm more house to be safe, a second washing machine and leave the light on at night, you might need it and the 30 euros a year for LED are also trivial! But seriously: for many, a 300L storage tank is plenty, and even then, there is often reserve. As mentioned above, smaller tanks also recharge faster. Especially with a heat pump with low output, this is also a factor. If there is such a high demand, you rather need a bigger heat pump. Incidentally, with my brine heat pump, a smaller storage tank is even an advantage, because with a shorter charging time the brine temperature does not drop as much. Otherwise, it can be said that it is basically a good device and it definitely works, and of course you don’t really notice the xx euros more or less, they are missing from the start and continuously. And oh yes, about the annual performance factor Gym: the 6kw device has a COP of almost exactly 3 at -7 degrees air temperature and 30 degrees flow temperature, only 1.8 at 50 degrees. So there is already a difference in the cost per kWh heat, at 20 cents per electricity kWh that is already your 5 cent difference, so you must not neglect the cold days.