Renew 28-year-old gas heater

Hello,

we have purchased a semi-detached house where a gas heating system Buderus G_124LP (year of manufacture 1992) is installed.
On the internet, it is often mentioned that heating systems older than 15 years are quite uneconomical. Now the consideration is to replace the heating system in the short to medium term.

The BAFA offers certain subsidies for gas hybrid heating of 30% and “Renewable Ready” gas condensing heating of 20%.

The house has a south-facing roof, and the previous owners had equipped the entire roof with a photovoltaic system (28 panels).
The photovoltaic system was not sold and has been dismantled. However, the cabling from the roof to the basement remains, so a new system can be connected quickly.

Now I wanted to ask for your experience regarding what the most economical option would be here?

A new gas heating system combined with a solar thermal system to receive the BAFA subsidy. The rest of the roof could possibly still be equipped with a photovoltaic system, or rather a simple gas heating system with the option to install 28 photovoltaic panels again.

The natural gas consumption of the previous owner was about 15,000 kwh (4 people) and is a good benchmark for us.

I am very much looking forward to your suggestions and recommendations.

Thank you,
Dieter

We are in a similar situation. In our newly purchased terraced house there is a gas condensing boiler from 1997 and we would like to replace it before it breaks down. The associated water storage tank was replaced by the previous owners in January, so it is brand new. The consumption of the previous owners (2 people) was always between 15,000 and 17,000 kWh in recent years. In our current house, we are four people and currently have a similar consumption (but without hot water) and pay about 700 EUR for gas per year. The consumption for four people will probably be slightly higher, but honestly, even at 900 EUR per year, I don’t see how a hybrid heating system could ever pay off over its entire lifetime. So it will probably just be a direct 1:1 replacement with a current model.

The consumption for four people will probably be somewhat higher, but even at 900 EUR per year, to be honest, I wouldn't know how a hybrid heating system could ever pay off over its entire service life. So it will probably just be a one-to-one replacement with a current model.

Calculating is probably the crucial question. Of course, the subsidies are interesting and an incentive. In the case of , even more so, since a base is already there. Basically, photovoltaic is interesting because energy is not getting cheaper. In addition, you invest today in a system with the "state of the art" and have peace of mind for the next 15 to 20 years. I would have both calculated by the plumber I trust and decide based on the figures.

So fill the roof completely with photovoltaics again. Keep the gas heating as long as it runs. However, you can optimize it. The keyword is, for example, thermal balancing.