Hm.. Good question. Very individual.
Well, geothermal energy.. We want to build a low-energy house this year, which, due to good insulation, already consumes much less energy than a "conventional" house, and we are also facing the question of what heating system to choose.
Under no circumstances do we want those rather ugly radiators anymore. Besides, they take up living space.
Of course, no oil or gas either, that keeps getting more expensive, obviously.
If you have a passive or even energy-plus house, you hardly need additional heating; then solar and maybe a wood stove or something are sufficient.
For a non-passive-but-below-KfW60 house :), like the one we want, we are choosing underfloor heating, which is run by water.
To operate it, there are several solution approaches. Electricity is expensive and getting more expensive, especially since oil/gas prices keep rising, and electricity providers justify their price increases with this.
You can very nicely combine underfloor heating with solar energy; the solar collectors feed your hot water tank with heat, i.e. heat the water that you can, for example, use for showering, but which can also partly serve your underfloor heating.
If you – especially with a well-insulated, i.e. very airtight, house, highly recommended – also install an automatic ventilation system (also not that cheap but definitely worth it), then this system automatically ventilates your house (any remaining moisture goes out, you don’t have to ventilate manually anymore), and the system can filter the residual heat contained (from showering, cooking, simple body heat, stove, etc.) and feed it back to the supplied fresh air – or even transfer the residual heat into a storage unit, which can then feed your underfloor heating, thus creating a quite cost-effective solution.
To what extent this pays off individually can only be told by a specialist who knows all the complete values; and then you have to calculate the purchase/installation/maintenance costs over the next 10, 20, 30 years and see what works best for you.
By the way, per person in the house, you need between 50-100 liters of hot water storage per day; depending on the type of collector, that is between 1-1.5 sqm of collector surface per person.
To run heating purely via solar collectors, however, you need a solid approx. 1 sqm per 5 sqm of living space! – Hardly anyone has that much space on their roof, and it costs a ton; but possibly you get financial support from KfW, federal/state/municipality;
for us, that meant, since we will have a hip roof with not much space on it, and a tight budget: solar collectors for hot water preparation: profitable; for underfloor heating? – Rather not, at best as a small addition if there is enough sun. So also an air supply and exhaust system, which we need anyway for a – massive! – low-energy house. No mold, always fresh air, extracted residual heat is used.
In winter, if the solar system maybe no longer suffices for hot water, then a wood stove that is integrated into the system; the wood stove heats the water in the hot water tank, which can then also supply the underfloor heating.
If you have a few branches from the wood stove, you can also pipe them into the upper floor, where e.g. the bedrooms and children’s rooms possibly are. And maybe also into the (party) basement?
- For wood stoves you also need space for wood (split logs, wood chips or pellets), of course. And pellet stoves & Co. are not that cheap either. 12,000 can definitely happen.
Besides, you must also pay for the chimney sweep who regularly inspects it.
Geothermal energy.. well, the brine systems are said to be the most effective, but they probably cost around 18,000 euros or so.. Sure, you might get a subsidy; and, sure, oil/gas do keep getting more expensive, and eventually it pays off.. however, I have often read that geothermal energy only pays off after about 20 years, and NO ONE guarantees you (except maybe for 10 years or so) that you will get heat from the earth forever; that means: eventually new, very expensive drilling might be necessary.
Aside from that – although I am not an esoteric person – I feel a strong aversion deep inside at the thought of driving a nail 150 or 200m deep into "Mother Earth".. And whether you hit a good spot right away or need more drillings is uncertain.
And whether your expensive geothermal system will still work in 20 years is another matter.. I think wood stoves are easier to repair / replace cheaper.
And, yes, you also need electricity for geothermal heating.
- This is really a very difficult question that only everyone can answer individually based on their individual house and the financial framework they set themselves.
The better insulated a house is, the less (heating) energy one needs, and possibly also less electricity.
In this respect, you have to calculate roughly what you need annually, consider a possible family with children in a few years, and then plan your heating and hot water system.
If you are building new, you should stuff everything with empty conduits :) just to be sure that you can still add electric cables and things like a solar system later without much trouble and dirt (and enormous extra costs).
Best to do an energy consultation at the consumer advice center and have them calculate the best system for you; such consultations are usually even free.
Best regards, Honigkuchen