About an hour?

More for my record than any other consideration.

It started back here, When the usable light was from   ≈ 04:30  - 21:00.
Now it's down to a much shorter period, guessimetric ≈ 07:00 - 18:00

I'm also, now suspecting the logic of the system.  Seen in extra - for ME.
;¬)

1. It's easy to grasp the concept of 
"Less light = less electricity generated = Battery not 'filled' up."
2. It's equally obvious how the Fridge/freezer cuts in at intervals through night; requiring grid due to "flat"  battery.
BUT!!!
The bit I can't wrap the olde swede around is this:-
It matters not, one Tittle, or Jot whether the house drew ≥1kW, or as little as 100W it was all exported other than enough to keep Battery ≈ 10% charged.

I'll watch for a day or two then consider the Telling Bone &/or look at the Blip where bloke diagnosed& rectified by phone.

November next.