Electronics and appliances waste a lot of energy when they're plugged in but not being used. There's even a term for all that waste—"vampire power." A home entertainment center in standby mode, for example, can draw as much electricity as a refrigerator.

A range of new devices offer to help you manage this problem. The latest is ThinkEco's Modlet, a gizmo little bigger than a "wall wart"-style plug that packs enough brains to continuously monitor the energy usage of any device plugged into it. ThinkEco claims the Modlet can reduce a household's overall energy consumption by 6 to 10 percent.

Via an interface on a desktop computer or mobile device, a homeowner can shut off Modlet-connected devices and set on-off schedules for them. The devices are controlled wirelessly through a short-range wireless standard called ZigBee that's designed for home automation.

A Modlet communicates with a user's computer wirelessly, through a USB dongle, doesn't require a smart meter, and can operate independently of a computer. It will arrive in big-box stores and a major online retailer sometime in October.

Its functionality and price—$45 for a Modlet, or $50 for a Modlet and USB connector—make the Modlet a hybrid between full-on home automation and a simple timer switch.

Simpler devices already on the market, such as Belkin's Conserve, consist of power strips and individual plugs that can be switched off manually (or put on a timer) in order to stop devices from drawing power when they don't need it.

General Electric is rolling out a more sophisticated energy-management system, in which a device called the Nucleus acts as the hub of a home's energy-management features. The Nucleus is a three- by four-inch computer that plugs into any wall outlet. It can connect wirelessly with a home's smart meter (if it has one), and with compatible appliances, providing a user with the same information that utility companies receive.