ᐅ Remove oil heating, install gas condensing boiler plus solar?

Good day to all readers!

Recently, as I do every two years, I attended the ISH trade fair in Frankfurt. After such an event, you naturally start feeling interested in new home technology. My oil-fired central heating system (Viessmann Vitola 200) is now 20 years old and runs perfectly; even the chimney sweep is satisfied with the readings. Objectively, there is no reason to replace it yet.

On the other hand, I consider myself a responsible person who likes to contribute to making things better. Last year, I replaced my diesel car with a natural gas vehicle, and I also switched to a genuine green electricity provider. Emotionally, I would definitely like to stop burning oil in the future, as I now regard it as almost unforgivable.

Gas supply is available in my street in a suburban area of Berlin. My roof shape is not ideal for solar thermal systems but also not completely unsuitable. It is a half-hipped roof with a north-south ridge, incorporating four dormers. I estimate that about 12 square meters (130 square feet) of collector area could fit on each side in the central section, but this would need to be examined more closely if I proceed.

The space currently occupied by the oil tank I would rather use for a private sauna and cancel my gym membership. I pay 1,000 EUR per year and rarely go due to lack of suitable time slots. The same applies to my father, so that would be about 2,000 EUR per year saved—enough to cover the cost of a sauna.

There would also be room for a sufficiently sized buffer tank. Another aspect is that my main workrooms are located in the basement, which tends to be too cold in summer. From April to October, I switch the system from heating to hot water only.

Now I am wondering: If I install a gas condensing boiler combined with solar thermal, I would ideally have enough hot water in summer and could warm the basement workrooms a little, while using little to no gas. In winter, my gas consumption would likely be less than my current oil use, since a new system would obviously be more efficient than my 20-year-old one.

The downside is that I have to consume gas as I buy it, and can’t purchase it when prices are low, unlike oil, which I can stockpile for over a year and buy when prices dip. Currently, I use about 3,200 liters (845 gallons) of heating oil annually to heat roughly 300 square meters (3,230 square feet) of living and usable space. That’s already significantly better than the national average.

So here is the big question: Is it sensible to switch now, or not? Will it actually improve my energy and cost balance? I assume I will have to switch within five to ten years anyway.

Thanks for all helpful thoughts!

Matthias