That 6 kW is probably midday, summer, sunny - the total of the panels’ rated output. Usable output will be a fraction of that. And, I doubt that they have a battery bank and an inverter. The panels are probably just tied into the grid where there will be zero noticeable difference in the Hut’s monthly utility bill.
Sham.
My 100 watt panels put out within 5% of that most of the year — say 8-9 months — when it is sunny and I’m at 46°N. At peak they can go over rating by 10% or so.
Of course, to get the output I reported in #18, the panel orientation has to track the sun — and even then it isn’t going to be for very many hours each day once you get much away from June in the northern hemisphere.