AC power supplies
Keep them from zapping your wallet and the environment
You may not think much about power supplies, those power cords with a bricklike appendage that converts AC power into the
DC needed by cell phones, laptops, and a host of other devices. But touch that brick while any of those devices is on and
it will probably feel warm. That’s the energy lost during the conversion process. The power supplies hidden within desktop
computers, TVs, cable boxes, and other appliances also waste energy.
With typical use, AC power supplies can waste $20 to $50 of what you spend annually on electricity. Nationwide, power supplies
waste more than 58 billion kilowatt-hours yearly, equal to the annual output of 10 large power plants. That extra energy output
translates into 40 million tons of the greenhouse gas carbon dioxide released into the atmosphere each year, according to
Ecos Consulting, an environmental consulting firm.
A major culprit in this waste is the type of adapter known as a linear power supply, or transformer, which typically has
an energy-efficiency rating of 30 percent to 60 percent. That means it loses 40 percent to 70 percent of the energy converted
to DC when powering an appliance. A transformer can consume 2 to 5 watts just by being plugged in. Manufacturers like them
because they’re inexpensive to make.
More-efficient designs, called switching power supplies, can offer up to 90 percent efficiency. They use far less power,
even when not powering an appliance. They also cost slightly more to produce.
As of Jan. 1 2005, the Environmental Protection Agency is expanding its Energy Star program to include external power supplies.
Initially, to qualify for the seal, a power supply’s average efficiency must fall in the top 25 percent of units on the market.
Energy Star-rated external power supplies should start reaching consumers during the first half of 2005. The Energy Star
logo will be on the product box, but not on the power pack itself. That could mislead consumers about whether the rating applies
to both the power supply and the device with which it comes. But Andrew Fanara, team leader of the EPA’s Energy Star program,
says that the language on the box will be clear.
Although most power supplies in use are internal, the Energy Star program won’t cover those until at least the end of 2006
because they’re more complex, Fanara says.
Some devices not now rated, such as cordless screwdrivers and handheld vacuums, also won’t be rated before 2006: Members
of the Association of Home Appliance Manufacturers, which produce them, have yet to join Energy Star because, the association
says, such testing isn’t yet appropriate for those products.
But come Jan. 1, 2006, manufacturers might have little choice about complying with new energy rules. That’s when California
deploys new requirements for external power supplies. According to the California Energy Commission, the new standards will
be in line with Energy Star, and compulsory. The mandates might have a powerful effect on industry compliance nationwide,
since few companies will want to be excluded from the sizable California market.
Ecos Consulting is leading an initiative to make power supplies for desktop PCs more efficient. Energy Star now covers PCs
only when they’re in sleep mode. Ecos’ program, 80 Plus, requires a power supply to be at least 80 percent efficient even
while the computer is in use. Intel and the EPA are working on another initiative, but with less stringent standards.
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