I've been computing the stats for the longest gap for laptop off-grid
and wind power for most of October and November, and the worst gap for off-grid
(which is essentially a fairly-full solar PV battery charge)
is about 3 days in November and 5 days in October (strange that October is worse).
The implication is that a truly off-grid system would need 5 or more days
of battery capacity given my PV and siting though the average is ~1 day.
Wind is showing a gap of well over a week and ~1% availability,
which suggests that it really isn't a contender in my part of London.
Rgds
Damon