Renewal of heating system in old building, which system?

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Who uses the apartment and how?

The idea is good, but we want to use the apartment ourselves. Possibly short-term rental occasionally. We wanted to remove the old oil heating system because we also want to gain the oil tank room as a usable cellar.

So far, we have been considering installing low-temperature radiators on the first floor so that we can operate with a maximum supply temperature of 55 degrees. We have so far avoided converting the first floor to underfloor heating because then we would have to replace all the floor coverings, etc. The living area is approximately 91 sqm. What would the conversion to underfloor heating and floor coverings roughly cost us? The new radiators cost us about 2,100 EUR after subsidies.

Of course, we could consider operating with a maximum supply temperature of 40 degrees on the first floor, then we would see if we even need it warmer. Here in Munich, recent winters have mostly been very mild. Additionally, there is a tiled stove installed on the first floor (we would have to retrofit it because it has to be decommissioned in 2020).

Another hybrid option with a gas heating system and a small heat pump has also been offered to us. This option would also be eligible for subsidies.

What would the conversion to underfloor heating and floor coverings approximately cost us? The new radiators will cost us about 2,100 EUR after subsidies.

This cannot be answered as such. It depends on the build-up height of the floor (remove everything and underfloor heating + screed, possibly thin-layer process, milling), your wishes for the floor coverings (4.99€ laminate, 40€ tiles, or 120€ luxury parquet) as well as possible own contributions (removing the old floor or laying heating loops can be done very cheaply by yourself, for example).

Well, that's great, then the heating company can contractually guarantee that to you and assure you a right of withdrawal for 2 years if the annual performance factor is not reached. If you yourself have no interest in thoroughly researching, I say: smallest gas boiler, 200l storage tank, and that's it. Nothing big to adjust, no hassle with the technology, and it will get warm. You must realize yourself that 24KW is too much for an (estimated) 11KW heating load. There are wonderful manufacturers that offer 11 or 15KW boilers and have a low modulation limit.

The photovoltaic system should cost about EUR 19,000 net including storage subsidy.

I now have a current offer without storage (which even the solar installer advised me against). Net EUR 11,700 for 9.9 kWp – without subsidy, but with all necessary services and work. Just as a comparison.

Yes, what makes me suspicious is also the calculation of the standard heating load by the heating company (with heat pump offer):

Standard heating load 21.86 W/m2 corresponds to 200m2
-> 4371.45 W

I have now done further research myself and found an online calculator for heating load estimation.
When I enter my data there, I get a result of a standard total heating load of about 11,000 W.


Furthermore, the company calculates the power for domestic hot water heating with 7 persons in the household and 37.5 L / person / day and an annual utilization factor of 0.4 and daily full usage hours 4h / day
-> 6697.35 W

Total heat generator power
-> 11068.79 W (11 kW heating load of the building)

This means that with the standard total heating load calculated by myself, I would come to a total heat generator power of about 17,700 W, so rather about 18 kW.

That means 18 kW / 3.5 x 2000 = 10,285 kWh electricity consumption for the heat pump (in the worst case 3.5 seasonal performance factor). With a heat pump tariff, that would be about 2,500 EUR electricity costs / year.

I now have a current offer without storage (which the solar installer even advised against).
Net 11,700€ for 9.9kWp - without subsidies, but with all necessary services and work. Just as a comparison.

About 1,200 EUR net per kWp is not bad, right? In which region do you live? In our Munich region, there are often different prices (I have noticed).

thx

In the Munich region, there are often different prices (I've noticed).

That is a reasonable price. It would be the second system from this solar installer.
The region does not matter. The price applies to Brandenburg just as it does to the Rhineland (where I live) or Munich. It is a smaller company from 08280 Aue-Bad Schlema, which operates nationwide.