I've flown numerous times this year on Fridays at SFO, at various times of the day, and I've never had to wait more than 5 minutes at the security line, and there was always a free EasyCheckin kiosk.

I never have checkin baggage, and do OLCI. I usually plan on arriving at the airport 1 hour prior to departure in case something goes wrong, but sometimes have arrived 30 minutes prior to departure, breezed through security, and got to the gate as seating 4 was announced.. a little too tight, but didn't miss the flight.

I'd say 45 minutes is plenty of time unless you are checking baggage.