Parking is San Francisco is very difficult and expensive.
Most hotels charge extra for parking.
Street parking is as easy to find as winning the lottery. The city owns a few very high tech lots near busy areas such as Union Square which are not too bad. Taxi's don't have to park and save you a lot of stress. Basically, the only good thing about having a car in S.F. is travel to outlying areas such as Napa and Monterry. Within the city, it is highly counterproductive.