ᐅ Heating system replacement for a renovated semi-detached house previously using gas

Hello everyone,

We are a family of four, with two elementary school children and parents working from home extensively. We are considering replacing our existing heating system but are unsure which type would be best for us. We would greatly appreciate your comments, experiences, or suggestions.

Let me describe our property and the conditions: we have a semi-detached house built in 1935, with about 140 sqm (1507 sq ft) of living space. However, it has undergone many renovations in the last twenty years. We currently have a gas heating system from 1998 by Buderus with a 200-liter (53-gallon) water tank. We have a photovoltaic system of nearly 9 kWp, no battery storage, and for a year now an electric heating element in the water tank. Since our house already has wall and ceiling insulation, as well as double glazing (plastic windows installed around 2000), our gas consumption over the last twelve months was 900 cubic meters, which is quite low. We do not have underfloor heating but radiators throughout. The living/dining room also has a wood-burning stove, which we heat with our own wood. Last year, we turned off the heating system completely from June through October, as the electric heating element powered by the photovoltaic system worked very well. I will probably switch off the heating again after next week for about half a year.

However, the heating system is already 26 years old, which makes me a bit uneasy. Our chimney sweep said the system is "still in good shape," but it will likely fail within the next five to ten years. There are heat pumps, combined heat and power units, fuel cells, or, if still permitted, a gas boiler. A wood gasification boiler could also be an option, but I’m not getting any younger, and three meters (about 10 feet) of wood per year—plus another three meters each for my parents and parents-in-law—is enough work for me. 🙂

On one hand, I don’t know what would conceptually suit our house best. On the other hand, the purchase costs are quite daunting: a new gas heating system would cost me 5,000 euros. The other options are about four to eight times more expensive. Considering that our annual heating costs are about 1,000 euros, I am hesitant to invest over 20,000 euros in a new system.

I would be very grateful for any responses!

JachCarver987 schrieb:

I’m quite hesitant to purchase a new system costing over 20,000 euros.

You don’t have to change anything. If something breaks in the gas system, you can have it repaired.

JachCarver987 schrieb:

So I would be very grateful for your answers!

I wouldn’t change anything at the moment. You could already spend about 200€ (around $220) to have a room-by-room heating load calculation done or to size radiators for heat pumps. You might also consider replacing radiators now and lowering the temperature of the gas heating system.
That way, in 5 to 10 years, you can decide spontaneously and be prepared.

JachCarver987 schrieb:

Considering that our annual heating costs are just 1000 euros,

Which is okay, but not particularly cheap. With current electricity prices, I would estimate savings of about 30 to 50% with a heat pump.

Thank you for your responses! I had also roughly estimated the savings to be around 30 percent. However, the heat pump will only pay off after several decades. So, the likely approach is to keep operating the gas system as long as it is allowed/possible?

I wouldn’t count on spare parts for a 25-year-old gas boiler. Mine is 22 years old, and no parts are available anymore.

Is it a condensing boiler?

Do you have a firm quote for replacing the gas boiler?

Whether gas will be available and at what price is unpredictable.

There is a KFW program (448) offering up to a 70% subsidy if you install, for example, a heat pump.

JachCarver987 schrieb:

The heat pump will only pay off after several decades. So the strategy is probably to operate the gas system as long as it is allowed/possible?

Yes, definitely.

However, personally, I expect a much faster payback due to the introduction of free pricing for the CO2 tax starting the year after next. I believe that in five years, the discussion around continuing to operate heating systems fueled by fossil fuels and the payback period for an investment in a heat pump will look very different (falling prices for heat pumps also play a role – fixed prices for a full replacement from gas to heat pump are already below 20,000 euros before incentives).

Addendum: The above price is BEFORE subsidies.