A green anti-tip

I feel strongly that energy conservation is important. For that reason, it bothers me when I see bad advice passed off as "green tips." One I've seen frequently is the suggestion that you should buy a power strip with a switch and plug your cell phone charger into it, so you can turn it off when you aren't charging the phone. It sounds logical, but in most cases it won't save any noticeable amount of power.

Modern wall chargers are usually very efficient and draw almost no power when they're not actually charging a device. I did an experiment with my own cell phone charger by plugging it into a wattmeter, a device that measures power consumption. It used less than one watt with the phone disconnected, too little to even show on the wattmeter's display. I plugged a power strip into the wattmeter and plugged in all three of the chargers I normally use — phone, laptop, and camera — and found that all together they still drew less than 1 watt. This represents less than $1 per year at the current average U.S. electricity rate; compared to the rest of the power used in your house it's completely lost in the noise.

A simple check to see if your charger is of the newer, more efficient type is to feel its case after it's been plugged in but not in use for a while. If it feels warm to the touch, you'll save at least a little power by disconnecting it. If it's cool to the touch, you might as well leave it plugged in.

You could argue that disconnecting cell phone chargers when they aren't in use doesn't really hurt anything. I feel, though, that if we're going to ask people to invest time and money into conservation, we ought to make sure we're only asking them to do so when it will actually make a difference.