The Kill-a-Watt monitor plugs directly into an outlet and immediately presents basic information about a device's electricity usage. It is very easy to use.

The Watts Up? monitors are more sophisticated. Three models of the Watts Up? monitors are available. Key differences are that the standard model does not offer a PC serial port interface. The basic Pro version does, and will record up to 1,000 data points. The Pro/ES provides additional data storage, up to 13,000 data points. Finally, the RT software, an enhancement for the two Watts Up? Pro models, allows "real time" viewing and graphing of data along with automatic email notifications.