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Do Phone Chargers Waste Power?

Peter Svensson, Associated Press (
Tue, 03 Apr 2007 20:30:36 -0500

Question: Do Phone Chargers Waste Power?
Good Question: Straightening Out Cell-Phone Chargers and Their Power

By PETER SVENSSON The Associated Press

- Q: Does my cell-phone charger consume electricity if I leave it
plugged in to the wall when it's not charging the phone?

A: It probably doesn't consume a significant amount, unless you have a
really old cell phone. You may have heard that "all power adapters use
electricity if you keep them plugged in," but it's not quite true

I used an inexpensive P3 Kill A Watt electricity meter to test six
cell-phone chargers from five manufacturers, and found that none of
them used a measurable amount of power when not charging a phone. None
of them were older than a few years. One of them did use power when
connected to a fully charged phone, but it was less than half a watt.

If you have an older charger, you can test it by plugging it in, and
then feeling if it gets warm to the touch. That may indicate that it's
a so-called "linear" power supply. These are generally larger,
bulkier, and less efficient at turning alternating current from the
power grid into direct current usable by an appliance.

Modern chargers are called "switched-mode" or "switching" power
supplies, and use chips to convert AC to DC. Some of the larger
versions of these adapters, like the ones built into computers, do use
electricity when the appliance is off. The Kill A Watt widely
available online told me my desktop PC uses 2 watts when it's off, as
does the hefty power brick of the Xbox 360 game console. The adapter
for my wireless router uses about 1 watt. A few other adapters used
about a third of a watt.

The wattage numbers aren't large, but they add up, especially when you
consider appliances that don't really turn off, like DVD players that
remain in "standby" mode. My laser printer, for instance, doesn't have
an "off" button, and sips 6 watts, according to the Kill A Watt. That
costs me $10 a year.

To cut off these trickles of electricity, you could connect your
appliances to a power strip and turn it off when they're not
needed. You can also look for appliances certified under the
U.S. Environmental Protection Agency's Energy Star program, which sets
standards for power used in standby mode.

The EPA has also taken an interest in cell-phone chargers, but their
focus hasn't been on power consumption when not in use. The problem is
rather that the adapters are often inefficient when they are charging.
With some chargers, less than half the energy ends up in the cell
phone's battery. The rest turns into heat.

The EPA has introduced Energy Star Criteria for power adapters, and
manufacturers appear to be responding. Last month, Motorola Inc. said
it would redesign all its cell-phone and accessory chargers to comply
with the standard. Samsung Electronics Co. began introducing some
Energy Star chargers last year.

According to the EPA, if every phone sold in the U.S. this year used
an Energy Star-qualified charger, the energy saved could light 760,000
homes for a year, or prevent greenhouse-gas emissions equivalent to
those of more than 200,000 cars annually.

On the Net:

Copyright 2007 The Associated Press.

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