ᐅ Alternatives to gas – how cost-effective are they?

Hello everyone,

We currently live in a house (built in 2015, rented) with the following energy consumption values:

• Household electricity: 3,000 kWh per year
• Air-source heat pump: 4,300 kWh electricity per year, heating output 13,000 kWh
• Solar thermal system: 1,000 kWh thermal energy

For our planned house, there is a gas connection available, but we are also open to alternatives. We estimate gas costs for heating to be about 800 euros per year and might spend around 5,000 euros on a gas heating system.

We have looked into solar options (both photovoltaic and thermal) to support or power an air-source heat pump, but financially it doesn’t seem to add up. Additionally, our house will have a gable roof aligned exactly north-south, meaning one roof side faces east and the other west.

• For the photovoltaic system, I initially considered a battery so we wouldn’t have to feed electricity into the grid for very little compensation and could instead use the generated power for the air-source heat pump. However, such a battery quickly costs upwards of 6,000 euros; for that price, you could pay for gas for 8 years. In other words, even if it were a perfect battery that supplied all the electricity for the heat pump at no cost, it would need to last at least 8 years. This doesn’t even take into account that the air-source heat pump itself is also more expensive than the gas heating system.
• I am skeptical about solar thermal because during the summer months, when the sun is strongest, you actually need the least hot water. Electricity, at least household electricity, is always needed.
• Is it possible to install a gas heating system if you only build according to the energy-saving regulations (e.g., EnEV / energy performance requirements) without installing anything on the roof? Or would that not comply with the maximum allowed primary energy demand?
• What about using only an air-source heat pump (like we have now in our rental)? Somehow it is so expensive that it never really pays off compared to gas, regardless of whether you have photovoltaic or solar thermal on the roof. Gas is just too cheap...

We are quite uncertain about the best approach. What would you do?

First reply. You are right. From a financial standpoint, alternative energy sources will never be more cost-effective than gas.

Second reply. The legislators know this too. That’s why they require us, through energy saving regulations, to use an alternative renewable energy source in order to get a building permit / planning permission. This can be, in addition to gas, solar thermal systems for hot water, or controlled residential ventilation, or photovoltaic (PV) systems, or the use of district heating from biogas, and so on.

None of it is financially worthwhile.

What to do? From a business perspective, you choose the cheapest option. Five square meters (54 square feet) of solar panels on the south- or west-facing roof provides hot water from the sun. And you think you’re saving money....Karsten

You have to consider the time factor. Looking at the long term, around 20 years later, it doesn’t really matter what you choose; projections show that it makes little difference. The cost difference over a 20-year period is marginal.

This assumes the systems last 20 years without major faults.

Nordlys schrieb:
First response. You are right. From a commercial standpoint, alternative energy sources will never be more cost-effective than gas.

Is that really the case? If I remember correctly, the payback period is around 15 years (gas versus air-to-water heat pump). Admittedly, this is a rough estimate, but it gives a general idea. Often, only the boiler versus heat pump and corresponding energy consumption are considered. The fact that a chimney, which also costs money, is mandatory for gas systems is frequently left out of the calculations. Maintenance costs for heat pumps are often criticized, but the regular visits from the chimney sweep are usually ignored.

Personally, it makes little sense to rely on a depleting energy source (crude oil, natural gas) that will inevitably become more expensive. Of course, predicting the future is uncertain, but unfortunately, the crystal ball is currently broken.

I have actually considered gas myself and don’t want to demonize it, but pretending it is the only reasonable and economical solution is simply nonsense. Whether it is cost-effective depends too heavily on the specific conditions (usage patterns, number of occupants, insulation standards, house location, etc.).

First of all, his current heat pump seems to have a reasonably decent, but not very good, seasonal performance factor.

What will help you further is a proper total cost calculation.

This includes everything needed, calculated over a 20-year period.

For example, this covers the already mentioned chimney, maintenance, the basic fee for the gas meter, and of course the expected consumption.
You should proceed similarly with the heat pump.

For price increases, you can basically choose what to assume, but I would take the average of the last ten years.

There is not much more you can do. Especially with price developments, it’s basically a guessing game.

Personally, I would try to go with a heat pump when building a new house. But only if I find a general contractor who does not charge an unjustified extra 10,000€ (around $11,000) for it.

If the price of gas or oil rises, electricity costs will also increase.