Instead of buying another sweater how about a gift that'll really cut the chill. Thermal leak detectors are as easy to use as a flashlight and will show you where the cold seeps in. The green geeks on your list might also like smart power strips that cut standby power loss; solar- and wind-powered chargers; and watt meters that tell you how much energy you're using—or losing. LED lightbulbs are still a novelty and might make good stocking stuffers for your energy miser friends. If they grumble, tell them they won't need to change it until Christmas 2027.
Thermal leak detectors
These gadgets find hot and cold spots. The Black & Decker TLD100's light changes color to show temperature fluctuations while the Kintrex IRT0421 gives a digital readout of the surface you're pointing at including a radiator or a hot pot.
Energy watt meters
In our tests, Kill A Watt and Watts Up were accurate and both helped determine how much an appliance contributes to utility costs. If you use the appliance less or at lower-cost times of day, you can save money. The devices can also help compare energy costs of an appliance you own now with one you might buy.
Energy-saving power strips
These strips include programmable timers or USB-connected sensors that cut standby power loses, which can total 8 percent of a home's electric bill.
Solar and wind-powered chargers
Harness the power or the sun or wind to recharge your cell phones and small electronics. The small chargers can also be used with a wall outlet or USB ports, but make a nice backup when you need one. Claims for the the Xantrax solar inverter say it can power small appliances during a power outage or camping trip.
There's a lot of excitement about the new LED lights, especially now that sizes are becoming more practical and the prices are falling. In our tests of the Cree CR6 downlight (which Home Depot sells as the EcoSmart GU24), it used 84 percent less energy than a comparable incandescent and 30 percent less than a comparable CFL. LED lightbulbs contain no mercury, can be used with dimmers, and last five times as long as CFLs.