Did you know that when you shut off your TV, stereo or many other appliances, they aren’t really off? Instead they simply draw much less power. Sometimes this is needed in order to retain settings or keep a timer running. Other times it’s just so that when you turn it back on, it turns on faster. Sometimes it serves no useful function at all. One example of the latter is the wall wart/power adapter that many small appliance use. Even when they’re not connected to anything, the adapter is drawing power. If it’s warm, it’s wasting electricity. The average appliance only uses 1 to 10 Watts in standby mode, but this adds up, estimates of the percentage of a home’s power that is used by vampire devices are usually in the range of 8-10%.
Many new appliances are designed to use minimal power in standby, older appliances are often less efficient. If you want to check your house for vampires, you can use something like a Kill-A-Watt meter. It’s available online and many hardware stores carry it. For things that don’t really need to be on all the time (like battery chargers) you can just unplug them, plug them into a power strip so you can really turn them off, or use special plugs that will shut them off when they only draw a trickle of electricity. More information about vampire power is available at Wikipedia.
Here’s a few more related links, all from the Department of Energy.
This site lets you estimate appliance energy consumption. You can use this to calculate the operating cost of existing items or compare potential new products.
These calculators allow users to enter their own input values (e.g., utility rates, hours of use, etc.) to estimate the energy cost savings from buying a more efficient product.
This page lists standby power consumption for a lot of products.