Which heating system for the 200 sqm new building?

Seriously , how do you come up with so much nonsense? The gas going from 50 to 200 is a bit exaggerated too, but otherwise you can only agree with guckguck.

You see, I ask myself the same question about your posts. My arguments are based on facts, which photovoltaic enthusiasts like to ignore. Fact 1 Return and Risk: "The DAX return triangle proves that for an investment horizon of 20 to 30 years, the annual return in the past was between six and nine percent. Short- and medium-term price fluctuations in stocks are compensated over these periods." The political developments have apparently passed you by as well, but just keep dreaming of your wonderful return that doesn’t exist. With a ridiculous 12 cent feed-in tariff, you won’t even achieve a positive return; you need self-consumption for that. And if electricity gets significantly cheaper, your calculation is wrong. Nobody guarantees you that either. Thanks to the heat pump tariff, I pay much less for electricity than usual and that without slapping such a thing on the roof with all its disadvantages.

The profitability of a photovoltaic system is completely independent of the electricity price development. I have already replied this to hampshire.

Let's briefly go back to energy consumption. If I feed in 2500 kWh at 10.5 cents (With current ordering, the fastest can get it on the roof in 3-4 months, then we’ll probably be there) instead of using it myself, I pay for this 2500€ let’s say 25 cents per kWh. Then I would rather consume this electricity myself. So I can increase my return with energy consumption, and the higher the electricity price rises, the higher the return as well. Or where is the flaw in my thinking?

That is completely correct. Higher energy consumption increases the already high return.

However, you cannot consume everything yourself, and photovoltaics are profitable even without energy consumption, but only under unusual circumstances with energy consumption alone. Increasing the share of energy consumption via storage is certainly attractive, but is still considered very uneconomical.

Of course, it is nonsensical that you can sell the overproduction in summer at the same prices as the small amount in winter, as well as for the purchase. But that is just how it is, and that is exactly the reason why photovoltaics are profitable through subsidies.

For example, to cover the base load of the house, lights, computers, start the cleaning machines early in the morning when the rooftop power is not yet sufficient...

But for that, I wouldn’t buy expensive photovoltaics; I’d rather pay for regular electricity.

It’s actually quite simple.

[*]The feed-in tariff decreases month by month. The registration date counts. The 12 ct have long passed. For registration in July 2019, it is still 10.64 ct for a system <10kWp.
[*]Energy prices in Germany continue to rise. Relevant literature is available, among others, from the BMWI. With a heat pump tariff, you are currently at 20-25 ct, with a standard tariff on average at 29 ct.
[*]A self-produced and self-consumed kilowatt hour is more lucrative than a self-produced and fed-in kilowatt hour.
[*]According to a simple logic, self-consumption is more lucrative than feeding in – and this is also politically desired.
[*]Photovoltaics deliver electricity depending on solar radiation (good conservative irradiation values are provided by PVGIS – provided by the EU).
[*]Electricity consumption in a household is not linear. Neither over the year, nor over a day or an hour.
[*]Batteries as energy storage serve to optimize self-consumption by temporarily covering the missing photovoltaic power and overnight so that no grid supply is necessary.
[*]Photovoltaic energy makes ecological sense if the components are ecologically manufactured – ROHS-certified components contain neither lead nor cadmium and are recyclable. (These are by far not all photovoltaic modules.)
[*]Standard photovoltaic modules were never developed for rooftop use. They are connected in series and generate very high voltages with all associated challenges such as fire protection, electrosmog, statics, the involvement of two trades in all work/repairs on the roof…

Reasons for a photovoltaic system are diverse:

[*]Attitude towards environmental issues
[*]Desire for more independence and autonomy from price developments
[*]Economic advantages
[*]Meaningful integration into an energy concept for the house
[*]...

Economic advantages include:

[*]Feed-in tariff
[*]Reduction of grid consumption
[*]Preservation / increase of property value (questionable with standard modules)
[*]...

Concerns / decisions for one system or another include:

[*]Health (electrosmog)
[*]Recyclability
[*]Service life
[*]Payback period
[*]Change in property value
[*]Effort in case of repair
[*]Aesthetics of the property
[*]Knowledge of own consumption behavior (not just annual consumption…)

Here, almost only the economic efficiency is discussed, and this is too short-sighted. I would not put standard photovoltaic modules on the roof that look terrible, always mean two trades on the roof, generate unhealthily high voltages, pose a fire load risk to the house, and lower the value of the house when resold – who buys, in 15 years, a shack disfigured with depreciated ugly photovoltaic modules?
We invest in the appearance of our house, consider colors, shapes, and materials, and then slap ugly boards on the roof – just because we cannot get out of the hammered-in cheap-is-cool payback mentality. Build houses that you like and that enable healthy and good living. With or without photovoltaics.

From 2022, no one talks anymore about “whether” photovoltaics, but about “which photovoltaics” are coming to the house. Then the low-energy house regulation applies.

You won't even achieve a positive return with the ridiculous 12 cent feed-in tariff; self-consumption is definitely necessary.

That is not correct. Even if you assume that the inverter has to be replaced after 10 years, we would still be in the positive range with feed-in only. And thanks to the tent roof, with our two-roof system with 6.3 kWp, we already have a system that is more designed for energy consumption.