ᐅ Solar / Photovoltaics from an Economic Perspective

Hello everyone,
what is your assessment of photovoltaic and/or solar systems purely from an economic perspective?

Without going into details.
Single-family house, 199 sqm (2,145 sq ft); 2 adults / 2 children; gas condensing boiler with underfloor heating;

I know it always depends on the individual case, but I would like to hear your opinions based on the points mentioned above and from those who have experience with the additional costs of such systems.

Thanks in advance.

Best regards

Photovoltaics have proven to be very economical for us (connected to the grid at the beginning of 2014). They pay off after just over 10 years when fully financed. We financed the system entirely and use 30-40% of the electricity ourselves (including for the heat pump).

Photovoltaic systems become more worthwhile as electricity prices increase and as you manage to maximize self-consumption (through optimizing usage). In my opinion, photovoltaic systems pay off sooner than after 10 years, especially if you consider the money saved by shopping at wholesale stores (like Metro). There are often discounts or vouchers around 100 euros. So yes, it is worthwhile.
Solar thermal systems are not cost-effective.

One often reads here that solar thermal systems are not worthwhile. Where can I find reliable information on this topic?
Please no hearsay.

Thank you!

A household of four people requires about 2400 kWh of energy per year for hot water, which at 0.07 €/kWh (gas) equals 168 € per year for gas consumption. The investment for a solar system is approximately 3000 € (2 collectors + 300 l (79 gallons) storage tank), meaning it takes about 18 years to recover the costs of the system and start saving (assuming gas prices remain constant). However, after 18 years, the system will likely need to be replaced. Conclusion: it is generally not cost-effective.

Assuming the solar system produces 100% of the hot water needs 365 days a year; otherwise, the situation looks even worse.