As Google Inc. grows, so does its appetite for energy.

The Internet giant has taken the unusual step of applying for approval from the Federal Energy Regulatory Commission to become an electricity marketer, essentially giving it the authority to buy and sell bulk power at market prices, just the way large utilities and energy traders do.

The company, which made the application last month through its Google Energy LLC subsidiary, says the change will help it better manage supplies for its own operations and give it greater access to renewable energy sources. The move offers an indication of just how much electricity large tech firms now consume in order to run their sprawling networks of servers and mainframes.

Although more than 1,500 companies currently have status as energy marketers, the vast majority are utilities or power generators. The move is unusual for a tech company, though some industrial concerns that operate stores or factories, such as fixture-maker Kohler Co., smelter Alcoa Inc. and grocer Safeway Inc, have approval from FERC.

Google's power usage is unclear; it doesn't disclose how many data centers it operates or where each is located. Last April, it said its data centers were the most efficient in the world, so far as it was able to determine, but declined to say how much power it actually uses.