The economic recession and a federal stimulus package prompted a old-ish idea in frugal gadgetry to take off in a new way: "smart" technology invaded homes and public works projects in hopes of making our use of fossil fuels more efficient.

Smart-grid technology monitors energy use and helps steer consumption to times of day when other people aren't using much electricity -- a time when it is cheaper to power appliances and more juice is available.

The federal government invested billions in a smart grid in 2009 that connects homes and apartments with power plants. Consumer-level devices took off, too. Google released a PowerMeter service that gives homeowners reports on their energy use on the Web or on mobile phones. General Electric and others promoted smart appliances, such as hot water heaters, that help further help control energy costs.

Most homes didn't have smart meters in 2009, but that leaves room for plenty of expansion next year.