Buffer storage tank for basement in combination with gas condensing boiler/solar

Hello everyone,

I am currently planning the heating system for our new single-family house. I will install a gas condensing boiler, solar panels on the roof, and a fireplace with a heat exchanger in the living room. So far so good. Now the question arises, what kind of buffer tank should I put in the basement??
I visited 3 heating engineers and heard 3 different opinions.
1.) A 1000L combi tank will be installed in the basement. All 3 heat suppliers feed their heat into different layers. The domestic hot water is circulated through the tank in a stainless steel corrugated pipe and heated on demand via the heat exchanger principle.
2.) Also a combi tank, but 800L. However, the hot water is in a water bladder located in the upper part of the tank.
3.) The fireplace and solar fill a 300-400L tank for domestic hot water. The heating water is heated by the boiler when needed.

Which option is the most sensible?

For your information, we have underfloor heating and radiators combined in the house.

Regards
Marlon

...I am currently planning the heating system for our new single-family house. I will install a gas condensing boiler, solar panels on the roof, and a fireplace with a heat exchanger in the living room.

This will certainly prove to be uneconomical. Solar thermal systems as well as water-carrying wood stoves usually do not pay off in single-family houses. Some kWh per year are "harvested," but the additional investments are disproportionate. When using a gas condensing boiler as a heat generator, I would always reduce the demand (15% rule)

best regards

With gas condensing boilers as heat generators, I would always reduce the demand (15% rule)

Regards.

What do you mean by the 15% rule?

Assuming it is worthwhile after all. Which option for the buffer tank would be the most sensible?

Best regards
Marlon

What do you mean by the 15% rule?

Better insulation than would be required with a solar thermal system!

...Assuming it is still worth it.

You are welcome to provide proof with your system. Install heat meters on the solar thermal system and wood stove. Compare the harvested kWh/year with the demand as well as the investment or capital service related to it.

..Which variant of the buffer storage would be the most sensible?

That has to be calculated based on the specific conditions. This includes, among other things, the actual demand for heating/hot water.
Alternatively, you can trust a salesperson and hope that it somehow works out. However, the probability for this is very low. ;)

Best regards.

I probably should have mentioned that my girlfriend will run a hair salon in the house. Therefore, compared to a normal single-family house, we have a higher demand for hot water, which is also evenly distributed throughout the day when there is sun.

I probably should have mentioned that my girlfriend will be running a hair salon in the house. Therefore, compared to a normal single-family house, we have a higher demand for hot water, der sich zusätzlich gleichmäßig über den Tag verteilt, wenn auch Sonne da ist.

No minor detail, but a decisive criterion! Best regards.