Absolutely, the material cost for such a system is about 7-10k strongly dependent on the battery. The other ~10k is for setting stuff up (which takes about 1-2days).

The small balcony systems can be setup by pretty much everyone. They also have the best ROI compared to bigger energy producers.

A reasonable sized solar power system with around 10kWp and 10kWh battery costs at least 16k€ in Germany when done by a professional. Depending on your power consumption in general this can be a bad investment even with a heat pump. Therefore I would separate this from the costs of a hwat pump, since it is not strictly required. Especially since you can get energy plans selling power for ~26ct/kWh.