House Construction Cost Estimation - Does this fit?

The advantage with electricity is that you make the process more environmentally friendly at the source, not at the consumer. Burning gas, oil, coal is always dirty. To make a gas burner or a car more environmentally friendly, you have to replace it. That is expensive and must be done by every homeowner, so it does not happen accordingly. With lifetimes for a car or a heating system of 15-20 years, many of the cars from 2035 are already on the road today and many of the heating systems are already installed. The perspective makes electrification so attractive. Today, electricity in winter largely comes from coal power plants, but in 10 years you can switch it to something else without anyone having to replace their heat pump because of it. Every improvement in the electricity mix automatically affects all consumers. That is the main reason why politics worldwide are focusing on electrification.

PS: "Batterie" is technically a very broad field with very different properties regarding weight, performance, cost and discharge. Accordingly, there will be different storages that interlock. From small home storage to large redox flow and for the winter other things will be considered, e.g. cooperation. The alpine countries get electricity from outside in the summer and only have to generate little power with their water reservoirs. In winter, the water battery can then be used.

The engineer shakes his head, lowers it, and leaves... Even well-intentioned studies on heat pumps show that the efficiency drops significantly at 50-55°C flow temperature. At 55°C, one has an annual performance factor of about 2.6. Even if we assume a gas price of 12 cents/kWh in the medium term and an electricity price of 30 cents/kWh, it just breaks even...

I should have added that my sister also has 24 kWp on the roofs, 2 electric cars, and a large home battery.

No, that's not how it works, I'm afraid I have to disappoint you. "Electricity" or electrical energy cannot be stored... fundamentally.
Edit:
Correct. It can be stored, but only very briefly, in resonant circuits...

Even the battery, if we get "picky," is not an electrical but a chemical storage... with enormous losses over storage and lifespan...

There are oil tanks from the 1950s that are still tight... my smartphone battery is dead after 3 years....

And "water battery"... the engineer chuckles, looks down, shakes his head, and walks away... try calculating how much volume you would have to store to make even a small contribution. That's nonsense, sorry.

Common sense might suggest some things here... but if you scale that to the entire demand... then it's peanuts. Unfortunately.

I should have added that my sister also has 24 kWp on the roofs, 2 electric cars, and a large home battery.

Hopefully not financed on credit. Otherwise, I have to wish her a speedy recovery.

And "water battery"... that makes the engineer smile, look down, shake his head and walk away... just calculate the volume you'd have to store to make even a small contribution. That's nonsense, sorry.

I recommend going to the mountains. I do that often, for example to Switzerland. In Valais, almost every side valley has a dam, a lot comes together there.

There are engineers who do everything the way it's always been done. And then there are those who see difficulties as challenges. Or as the nice quote goes, "If I had asked people what they wanted, they would have said: faster horses." ;)

There are engineers who do everything as it has always been done. And then there are those who see difficulties as challenges. Or as the beautiful quote goes, "If I had asked people what they wanted, they would have said: faster horses." ;)

It will amaze you, but YOU are demanding faster horses. Because your idea of storing electricity in reservoirs or batteries is technically nonsensical. The energy density of reservoirs or electrochemical storage is downright ludicrously low compared to that of green hydrogen or green CH4. So far, so bad.

I suggest you inform yourself for 2 or 3 weeks and then we can continue the discussion? ;)