Homes and businesses that generate their own electricity and sell back to the grid excess production that they do not use are "net metered" accounts, and their number grew by 38% in 2009, according to the Energy Information Administration.
In 2009, 96,506 electricity accounts were net metering in America, up from 70,009 in 2008. These homes and businesses are at the heart of distributed generation.
A total of 540 electric utilities in 2009 allowed for net metering. The terms and conditions of net metering programs vary widely.
I would be willing to bet that the number today of net metered homes and businesses is around 200,000, as there has been explosive growth in net metering around the nation in the last 18 months driven by a roaring solar market. Not all solar installations are net metered but many are.
But back to the 2009 data that show 55% of the net metered accounts were in California, with Colorado second at 7,804 accounts, New Jersey third, Arizona fourth, New York fifth. Pennsylvania was 16th in 2009, with 650 net metered accounts, of which 552 were residential and 98 commercial. Again there has been massive growth since 2009, and I know that today Pennsylvania has several thousand net metered accounts.
As the grid grows smarter and generation becomes more distributed, net metering will go from about 0.1% of all accounts in 2009 to a significant share of the electricity market. And go quickly.