Warm weather 'could fuel Californian power crisis'

The worst day in California's power crisis has partly been blamed on a warm snap.

Blackouts have been ordered by the California Independent System Operator after the state fell 1,000 megawatts short of the power it needs. A thousand megawatts is about enough to power one million homes.

The ISO declared a Stage 3 alert, the highest level of emergency. It blamed increased demand on a warm snap, less power from the north west and the loss of 1,400 megawatts because of a transformer fire.

There are fears a summer heat wave could drive up demand even further for air conditioning. Natural gas supplies are also tight and water supplies are down.

The ISO said 12,000 megawatts were unavailable because of plants lying idle, including some where officials say they haven't been paid by cash-strapped utilities for months and cannot afford to buy the natural gas they need to operate.

The ISO ordered the state's three largest utilities - Pacific Gas & Electric, Southern California Edison and San Diego Gas and Electric - to cut a total of 1,000 megawatts being used.

The utilities serve nearly 10 million California customers. SoCal Edison and PG&E officials said power had been cut to roughly 800,000 customers, while the San Diego utility cut power to 41,000 customers per hour.

The blackouts were the first since January, but they lasted four hours - twice as long as those two months ago - and were spread across a much wider area, from dairy farms in Chino to restaurants in San Francisco and homes near the state capital.