Detached house heated with solar, additionally gas/heat pump

Hello, my wife and I are going to buy a house with 150 m² of living space in beautiful Upper Bavaria, near Traunstein. It is detached and octagonal. At the moment, there is a large gas boiler in the basement, probably from the 1980s. I have never really dealt with such energy issues and accordingly have little knowledge about it. But I have the feeling that the heating is not optimal; the previous owners were a bit brief on the subject, and there is no energy certificate. What I have already considered is equipping the entire roof with solar collectors. Would that be sufficient as heating for me? Or will I still need gas? Or would a heat pump be better right away? Regards loko

I have never really dealt with such energy issues and accordingly have little knowledge about them. But I have the feeling that the heating is not optimal, the previous owners were a bit tight on this subject, and there is no energy certificate.

As far as I know, an energy certificate is now mandatory if you want to rent or sell the house.

I wouldn’t let myself be brushed off so quickly on this point... Besides the old heating system, the insulation is probably also insufficient by today’s standards... expensive renovations will then be coming your way!

What you also have to consider when choosing the heating system are the radiators or whether underfloor heating is installed or not... Radiators usually require a higher flow temperature which could possibly cause problems with a heat pump...

Solar alone will not be enough for heating... you also have to distinguish between photovoltaic systems that produce electricity (with which you can, for example, operate a heat pump) and solar systems that supply hot water...
The problem with solar is that electricity is hard to store, and especially when you most want to heat (in the evenings in winter), there is usually little sunlight...

I would see photovoltaic systems purely as an investment... whether you use the electricity for heating or sell it to the grid operator is a question of cost-effectiveness...

Dear loko!
Based on the information you provided, it is not easy to fully answer the questions. Essential information needed, besides the insulation standard of the house, also includes details about the number of users and their usage behavior. This also includes, for example, whether children are planned (high hot water demand, different cold-heat perception). Since you did not provide anything specific, we assume that the house still corresponds to the standard from the 1980s.
Before a heating system is planned and designed, it must be clarified whether a renovation of the property is to take place in the near future or will be realized later due to the budget. Of course, it is fundamentally important to ensure the supply security of hot water and heat; this is certainly a high priority with a system from the 1980s. If the system can be adapted through renovation measures, investment costs for the system and energy costs can be saved.
The heating system is designed based on a heat load calculation. This calculation indicates the required capacity based on the above-mentioned conditions. To carry out a heating renovation, several funding programs (BAFA, KfW) are available; corresponding advice and calculation can be provided by an HVAC specialist with energy consultant training.
Based on the heating demand and the possible energy sources (gas, oil, solar, pellets, etc.), an economic assessment is possible.
Since a gas connection already exists, for example, only low investment costs are incurred for a gas condensing boiler system (around €7,000 - 8,000 including chimney renovation). Solar collectors can make a useful contribution to hot water preparation and heating support. For 10 sqm of living space, about 1 sqm of collector is calculated, so a required roof area of about 15 – 20 sqm with appropriate orientation must be available (issues – dormers, roof windows, etc.). In combination with a modulating gas condensing boiler system, which adapts to the actual demand, a high level of comfort is ensured even in possible extreme weather conditions in Traunstein.
Regarding the question of whether a heat pump would be possible, this much:
Here the question is whether the heat emission into the room is done via radiators. For a building from the 1980s, we assume radiators. Basically, an air-water heat pump requires low system temperatures to guarantee heating, which is not ensured in non-renovated houses without underfloor heating.
Best regards, Erik

you also have to distinguish between photovoltaic systems that produce electricity (with which you can, for example, operate a heat pump)

Hi!

Jokes aside - here: economically and technically, please always add a :D!

Best regards,
TomTom.

Hey!

Just a quick note - here: economically and technically, always use an exclamation mark!

Best regards,
TomTom.

Why? With 100 modules and a basement full of batteries, that's no problem ;)

My point with this statement wasn't that you can operate a heat pump 100% with it or that it's economically viable, but I wanted to give the OP an example of how heating warmth in his apartment can come from his photovoltaic system on the roof ;)
Electric fan heaters would be another alternative :p