>Clearly, the router is pulling more current during the dip than the power supply on my solar circuit can supply.
>[...]
>Ideally, we’d want manufacturers to put capacitance to that effect into their router power supplies or at least routers. But we realise that capacitors cost a few cents each and aren’t really required on stable grid supplies. And manufacturing costs matter.
Weird this was being seemingly blamed on "puny power supplies", and that "ideally" manufacturers should be overspecing their power supplies to accommodate his use case. Does he also think manufacturers should "ideally" add a battery to routers on the off chance that there's a transient blackout?
More to the point, he supposedly has a "4500W peak solar sinewave inverter", and his router probably consumes no more than 50W. That 50W is unlikely to cause issues with such a system, and even if it was the straw that broke the camel's back, it's weird to blame it on the router, rather than the inverter or the entire system. If you had a take-home salary of $10k, blew it all on gambling, then your card got declined on a starbucks purchase, you wouldn't characterize this as "my coffee habit was using more money than my income can supply".
The 50W load (if that) isn’t the problem - a lot of cheap power supplies assume a perfect sinusoid which you get from a spinning mechanical source of electricity.
The inverter probably only does a few step approximation of a sin wave which is fine for most things, but clearly not for this power supply which browns out (I’m guessing during an extended period of 0v on the stair step sin approximation).
Whether your average power supply should be tolerant is unclear, but if it’s the only device playing up it’s clearly less tolerant of imperfect power than everything else.