Does the panel produce the same amount of energy every season?
I know that in most of Europe the production during summer months is way higher than during winter and that needs to be taken into account
San Fransisco is at about the same latitude as Gibraltar, so while he will see seasonal fluctuations unless he changes its angle of incidence (but hes laying it flat, so...) However, he will not see as big a difference as, say, somebody in Germany.