> "... handwavy crap ..."

handwavy argument. Yes, in the (sub)tropics the argument is even stronger pro-PV, not the least because it'll give you the opposite of heating - aircon - for free right when you need it. And considering summer heatwaves as have been seen the last few years "way north", that benefit will extend that way even if you wouldn't bother considering letting it "assist", if not fully replace, your heating. That said though, for 50° polewards and above, if you wanted to use PV in winter orient the panels vertically. If you can clad your too floor with shiplap larch so you can with PV panels. Given the price of timber ... there's a plan.

(only saying handwaving goes both ways)