Gene and Diane DeJoannis of Manchester, Conn., thought they had cut their electricity use to the bone. But to double-check, Gene, 66, a semi-retired engineer, installed a home-energy monitor that continuously displays the home's electricity usage in kilowatt-hours (kWh). In the following year, the couple cut their electricity use by an additional one-third and their annual bill by 15% (from $715 to $606), despite a 15% increase in their electric rate.

Home-energy monitors come in several models, but Gene made a good choice by purchasing a TED ($120; www.theenergydetective.com). The TED sits on the couple's kitchen counter, plugged into a nearby outlet. It receives data through the home's wiring from a processor installed in the circuit-breaker box. The processor is clipped to the main lines bringing power into the house. (The company says a "tech-savvy" homeowner or electrician can install it in 10 to 15 minutes.)

Initially, the DeJoannises aimed to lower their electricity use by finding more things to unplug around the house (such as the unused boom box with a digital readout in their daughter's former bedroom). Quickly, though, the TED helped them garner other savings. They realized, for example, that they didn't need the kitchen lights turned on while they watched TV in an adjacent room. Gene likens the TED to the miles-per-gallon display in his Toyota Prius, which "tells you how you're doing all the time and changes your driving habits."

A forthcoming model (the TED 5000) will also optionally monitor power generation from solar or other sources, and produce a net reading. Gene keeps his own spreadsheet of energy usage, but TED users can buy optional software called Footprints ($50) to log and graph their data.

Reprinted with permission. All Contents © 2009 The Kiplinger Washington Editors. www.kiplinger.com