There was a very recent GQ on this, at least one, very recently. A quick search within the last 30 days will provide you with all the dope.
In brief, it has been a complex of a number of factors. (1) Cal. only partly deregulating the utilities. The utilities ability to sell was regulated. so consumers would not have to pay more than a fixed amount. In addition, the utilities had to divest themselves of the power plants they had. However, providers, who bought the plants, selling the energy to the utilities could charge what they wanted, and have. Some have made tremendous profits. And the utilities were forced to cough up to get the power, since their ability to make new power plants has been severely limited to the environmental powers (“not in my neighborhood”). (This is a multi-faceted (1).)
(2) Demand has gone up beyond expectations, due to new industries, companies, etc., which use a lot of computers.
That in brief are the reasons, as I see it.