This post is part of our definitions series on “eco-lingo” and technical terms.

We all know that we should switch off appliances and gadgets when they are not in use. But many appliances and gadgets continue to use a significant amount of power even when turned off – these gadgets are called vampire loads or phantom loads, using what’s called standby power.

According to the International Energy Agency, standby power accounts for 5-10% of residential electricity demand (in part because of the proliferation of gadgets such as iPods, netbooks, Wii systems, and Tivo, among many others).

Why do we have all these vampires?

One very common reason is power adaptors. Power adaptors (those little boxes that make up most of the charger or power cord for your gadgets) convert high-voltage alternating (AC) current from the socket into low-voltage direct current for your gadget. The Economist estimates that as of the end of 2009, there were about 5 billion power adaptors around the world. They don’t come with off switches and will continue to consume power while plugged in even if no device is being charged. Many folks in the energy-efficiency field call power adaptors wall warts because of their “ugliness” in terms of energy efficiency.

Vampire loads also occur because many gadgets have features that don’t turn off even if the device is not in use (like the clock on a microwave), and many devices have “instant on” functions that wait for remote control signals.

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In his book “Sustainable Energy – Without the Hot Air”, David MacKay shows the results of an experiment he conducted to measure the electricity savings from turning off vampire loads.

Image credit: David MacKay

From the book (which is free and available online here), his description of the experiment (with British units):

I measured the electricity savings from switching off vampires during a week when I was away at work most of each day, so both days and nights were almost devoid of useful activity, except for the fridge. THe brief little blips of consumption are caused by the microwave, toaster, washing machine, or vacuum cleaner. On the Tuesday I switched off most of my vampires: two stereos, a DVD player, a cable modem, a wireless router, and an answering machine. The red line shows the trend of “nobody-at-home” consumption before, and the green line shows the “nobody-at-home” consumption after this change. Consumption fell by 45W, or 1.1 kWh per day.