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Put To The Test: Charging your Laptop

Green Building

Put To The Test: Charging your Laptop Blog Feature

By: EYA Pugrant on July 25th, 2011

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A few weeks ago, we wrote about using our Belkin Energy-Use Monitor to test the difference in energy savings between CFL bulbs and incandescent bulbs and we were able to see firsthand how much better CFL bulbs were for your energy bill. The current product of our energy-use interest? Laptops. Many of us plug our laptops in to charge and leave them plugged in for hours after their battery is full. We're curious to find out what the energy-use implications of this behavior is and whether we should pay more attention to unplugging our computer chargers when they are not actively in use.

We first plugged the energy-use monitor in with a basic Mac computer charger attached to the wall that was not attached to a laptop. While many say that it is important to unplug all chargers when not in use because they use up unnecessary “phantom energy,” we found that little to no energy was being utilized from the Mac laptop charger when it was plugged in and not in use. It is possible, however, given the nature of this watt mater, that the phantom energy cannot be read by this device. As a precaution, it is probably smart to unplug the unused charger regardless if you choose to reduce your energy-use.

Next, we wanted to see how much energy was used while the computer was actively charging. When we attached the charger to the laptop with a depleted battery, it yielded the following results:

Then, we were curious to see if it was costly to keep a computer plugged in even if it is charged. It turns out that even if the computer fully charged but still plugged in, it still would cost about $34 a year to run. While it uses less energy than when it is charging, it is still environmentally friendly and cost effective to unplug it when not in use.