Which storage/drinking water heating is used in district heating?

Good morning everyone,

I am still busy with my new build. It’s not exactly easy at the moment with the rising interest rates and all the political energy topics. However, things are getting concrete now and I have to plan the house connection room. Unfortunately, I have to build without a basement and therefore have very limited space. The district heating connection is now fixed.

The connection load will be about 8-10 kW. Underfloor heating everywhere. Household of 4 people. Only a small photovoltaic system (4.5 kW).

We are building in the town center in a commercial location and therefore have our living/dining and kitchen area in the attic. There will only be a kitchen unit there that requires hot water, so I want to save on a hot water pipe there and work with an electric instantaneous water heater under the sink.

I still have to supply two bathrooms. One on the ground floor, diagonally opposite the house connection room. And the main bathroom, directly above the house connection room.

Which hot water preparation would you now recommend to me that is modern and space-saving?

My variant considerations based on what I have researched so far (I am not a professional):

Variant 1, fresh water station at the house connection station:

My favorite variant would be a FW transfer station with an integrated heating circuit and an integrated fresh water station (instantaneous water heater). No storage. These stations are quite compact (about 120x75x40, wall-mounted). Unfortunately, this variant was now talked out of me because it is apparently only suitable for larger connection loads. For the fresh water, about 30 kW would have to be provided briefly, which costs a high power price and probably also stresses the system (controllers, valves, shocks, etc...) because in normal operation (without hot water demand) much less power is needed and then suddenly 30 kW when hot water is required. Unfortunately, I would have found this variant hygienic and very space-saving!

Variant 2, hot water storage tank:

The probably simplest and still quite space-saving variant could work with an under-counter storage tank (160 liters) and a simple FW transfer station with an integrated heating circuit and a drinking water heater that then heats the boiler. According to my sketch, I could probably fit that in. The only question is whether that is still modern (hygienic and technical) and whether a 160-liter boiler is sufficient (not much bathing)?

Variant 3.1, buffer storage tank with instantaneous water heater at the FW station:

I don’t know if I can manage that in terms of space, but the variant would be a buffer storage tank of 500 liters and an instantaneous water heater at the transfer station. Since I have little space and I have a feeling of quite high heat losses there, I'm not particularly convinced by this variant.

Variant 3.2, buffer storage tank with instantaneous water heater at the buffer storage tank:

For me, the same as variant 3.1.

What do you think about this? I am not a professional and do not know if I have understood everything correctly and haven’t overlooked anything or if I have all variants on the radar.

Of course, I will award all services to specialist companies. But I would like to go into the race with a finished concept so that I can accommodate everything in the end.

For variant 2, I have already put together the house connection room in PowerPoint.

Many thanks and best regards

Uhh... the instantaneous water heater is by far the most expensive domestic hot water heating system. How much do you think you'll save? You have to make openings for the cold water pipe and the drain anyway, right? I guess the plumber won't give you a discount of exactly 0 EUR for the hot water pipe. Maybe 50 EUR for the materials... Drop the nonsense.

I have also thought in the meantime that nothing is being saved there. My thought was whether one could save a circulation pump with the variant that has the drinking water station in the HA room, since the distances would only be very short if you don’t have to go all the way upstairs.

Which variant would you choose?

I would install a hot water storage tank. However, 160l is empty after the bathtub. It would need to be checked how long it takes for the water to become warm again.

What does the kWh of heat cost? What prices are to be expected in the future? Why is photovoltaic only so small? An instantaneous water heater or also a small boiler in the kitchen can definitely make sense. Immediate hot water is also simply a great comfort that can otherwise only be achieved with circulation.

So 13 ct/kWh. Future forecasts are of course difficult. But in the future, heat will be given more attention and possibly regulated soon. Price increases will probably be more difficult then. However, it is also rarely the case that anything has become cheaper when politics has interfered. Photovoltaics are so small because only one side can be used effectively.