Newly built single-family house - gas or air heat pump + photovoltaics + storage?

That's not really relevant. Either you keep the specified distances, or you don't. How the neighbor feels about it is legally irrelevant. I am also disturbed by all the cars on the street. Obviously, almost all of them comply with the valid regulations, which are obviously FAR too lax and far from the technically possible for new cars. Can I therefore have the street closed?

And with gas, I also rely on biogas and the like. The prices for biogas are reasonable

As already wrote, the resource expenditure for biogas plants is usually very unfavorable in practice, because maize is grown for these plants, which not only consumes land but also particularly depletes the soils.

The problem with hydrogen is the underground efficiency.

The problem is that we believe that exactly one technology will be able to do everything and that we find a serious disadvantage for each technology and focus on it instead of concentrating on specific application advantages. Hydrogen is an excellent energy storage with a sensational energy density. Storing energy in hydrogen is more lossy than in other storages. In use with fuel cells, hydrogen is extremely efficient. Methanol is also an excellent energy storage with a good energy density. As a liquid, methanol is easy to handle, production is making efficiency progress, and industrially produced CO2 can be reused for production. Methanol is suitable for powering efficient fuel cells. Current battery technology does not (yet) have the energy density to be used as long-term storage. With modern charging and discharging technology, they are extremely flexible with fast charging and good peak load capability. As powerful short-term storage, they are ideally suited—also in many (but not all) mobility applications with an electric motor. In the field of sector coupling, a number of other excellent energy storage options come into play. It is about the right energy carrier for the requirement and not about an all-encompassing leading technology. Do not let yourselves be guided by backward-looking skeptics; that guarantees leads to nothing. Better to take one or the other wrong path and make real progress that way.

Hydrogen is extremely efficient when used with fuel cells

Compared to the combustion engine, it could win. ;-)

No, of course hydrogen and methanol are something nice. And we will need both in huge quantities in the future. The only important thing is that the end consumer knows that it will not reach them. It all goes to industry. And even that will do everything possible to use as little of it as possible due to the exorbitant price.

Different picture: Many complain about wind power plants and electric cars and hope for hydrogen or e-fuels. You have to make it clear to them that driving with hydrogen/e-fuels means operating five times as many wind power plants as driving with a battery. And no – import does not work, it is much more expensive and not realistic at all, especially in 30 years.

First of all, there still needs to be a change in people's minds. The rising energy costs and a CO2 emissions price are painful but probably for that reason also effective measures. Ultimately, our daily behavior holds a huge potential for savings that takes effect immediately. Energy that is not needed in the first place is the most environmentally friendly. For this reason, I am also not very upset about fuel prices, even though I consider myself to be particularly dependent on the car.

Compared to the internal combustion engine, it could win. ;-)

No, of course hydrogen and methanol are something nice. And we will also need both in huge quantities in the future. The important thing is that the end consumer knows that it will not reach them. It all goes to the industry. And even the industry, due to the exorbitant price, will do everything possible to use as little of it as possible.

A different picture: Many complain about the wind power plants and electric cars and hope for hydrogen or e-fuels. They must be made clear that driving with hydrogen/e-fuels means operating five times more wind power plants than driving with a battery. And no - import does not work, it is much more expensive and not at all realistic in 30 years.

Our dear still "disaster government"... And by disaster I do not mean that it was disastrous. Only acted due to disasters. The shutdown of nuclear power plants was one of the government's big mistakes. It should have been handled differently. First the coal power plants, then the nuclear power plants. What is the use of shutting down nuclear power plants in Germany if at the border to France and soon more in Poland stand? With the high quality standards that apply in Germany, I prefer a few nuclear power plants in Germany rather than in France or even Poland to import electricity from there.

Thanks! It will be a Vaillant aroTherm Plus. We would position the air-to-water heat pump so that it does not point directly at the neighbor’s house. The direct distance would then be 8m from the air-to-water heat pump to the neighbor’s children’s room and 20m respectively to the other two neighbors, who are in direct line of sight to the air-to-water heat pump, but I hope that is not a problem.

You are admittedly in a very poor negotiating position, but I would still ask the general contractor about the surcharges. A €12K surcharge is quite hefty: the gas boiler, solar thermal system, and the necessary piping for those would be omitted after all; and air-to-water heat pumps are really not that expensive. If it is still possible and an option for you, you can also save the chimney and fireplace. You will save the gas connection anyway. In the arguments for the heat pump, you also mentioned photovoltaics. Are you installing a photovoltaic system?

If you decide on a heat pump and possibly photovoltaics, you are welcome to ask here again for some key points regarding the system design.

Good luck!