Depends when. Right now, with the economy down and a little luck in the weather, probably not that bad.
If the economy picks up, probably a problem.
If the Enviro's get their way and most of 4-Corners and Powder River Basin coal plants are shut down and Alberta shuts down its coal plants (and BC hydro sells to Alberta rather than Califonria), serious problems.
If I were a Californian, I would be real concerned for how the Canadian Premier has said they will decide on Koyota accords prior to the end of the year. If Alberta has to shut down all of its coal plants that produce most of its power, new transmission lines will be built and the electricity from BC Hydro will no longer come to California. That would be a huge loss.