Hey to all you NL people (we're in Den Haag) - I've been researching solar water heaters and they look really promising? I've read they even work in winter. Is that wishful thinking in a country like NL?
If there’s no sun you’re looking at a different energy source which typically means electricity so you’re back to the demand problem when the weather is poor regarding renewable power.
I guess you could look up the insolation values and do the math on how much water you use and how hot it needs to be.