Google has released an app that will help web user monitor the electricity they are using and could even lead to a 15 percent reduction in electricity used by households.

Google PowerMeter integrates into iGoogle platform, where users create a customised page with lightweight web-based applications. The PowerMeter is designed to show a granular, real-time view of electricity-consuming devices.

Although just a prototype now, consumers will eventually be able to opt in to use it, although no personal information will be shared between Google and utilities, the company said. The electricity data will be stored securely, and users will be able to tell their utility to stop sending data to the PowerMeter, Google said.

Most consumers don't have much data or context regarding their electricity consumption, according to Ed Lu of Google's engineering team.

Google's PowerMeter takes data from so-called 'smart meters', or advanced electricity meters and other electricity management devices. About 40 million smart meters are in use worldwide, with that number expected to rise to 100 million in the next few years, Lu said.

Google takes data from a home's smart meter and displays it in a graph. It can show the current day's electricity consumption compared to the day before, but the graph can be expanded to get a historical view of peaks and troughs in electricity usage, Google said.

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Google also plans to release application programming interfaces (APIs) for PowerMeter that would let other software developers build applications around it.

Google is making a strong push for agreements with US utility companies on how to standardise the data that's available from smart meters. In a position paper sent to California's Public Utility Commission, Google said that "the data from the smart meter needs to be available to the consumer in real-time and in a non-proprietary format".

So far, Google is letting its own employees test PowerMeter. The insights gained include at least two revelations about the electricity used to make toast and the inefficiency of 20-year-old refrigerators.

"One morning I noticed that my energy consumption was higher than normal," said Kirsten, a Google program manager. "I went into the kitchen and found that the dial on our toaster oven was stuck and had been on all night".

"It was already burning and the once white exterior was now brown. If I hadn't seen my energy consumption and known where to look, my apartment could have been toast," she added.

Microsoft has also released a similar tool that is aimed at helping businesses track their carbon footprint.

See also: Let Google organise your life