Last week I had a conversation with my favorite engineering friend, Lee Devlin. Lee’s articles have been featured numerous times here on the CleanTech Authority Network, and he’s the guy I turn to when I need advice about EE challenges. This time I asked Lee about Vampire Power Loss, which is a phenomenon in millions of homes nationwide in the USA and other countries.
When you leave appliances plugged in, they drain power or create heat – both of which waste power. A “smart” outlet – one that would stop the flow of energy for appliances when not in use — is a good idea. We have power bars that you can manually turn off, but no smart outlets? I asked Lee if it already exists, or if he knew how to build something like this. Maybe it would require an actual switch at the outlet? Ideally, it would be smart enough to turn itself on and off.
Below is an image taken from a recent National Geographic story we covered about saving energy at home. The bright red represents heat from the flow of electricity, even though none of the chargers are being used. This is a very dramatic display of lost energy. Keep in mind, though, that images from infrared cameras can be very misleading, because they read even the slightest change in temperature. They often give the false impression that there is a large amount of heat being generated, when it might only be a few degrees of temperature variation; mere milliwatts of power.
Lee responded to my question with the following tips: There is a device called a Kill-A-Watt that will measure the current draw on power cubes (down to as little as a watt) and help determine whether leaving a charger on is a cause for concern. However, most modern chargers don’t consume that much electricity with nothing connected and/or charging.
My iPhone’s power cube, for example, doesn’t even register a watt until I plug in the iPhone. Then it registers about 4 watts while charging and 0 watts after the phone is charged. The iPhone’s battery has a capacity of 7 W-h, which is about .07¢ worth of electricity. Even if I drained and charged it every day, it would use only 25¢ in electricity per year. It would be hard to justify spending very much to prevent this minimal loss. Suppose there was a device for $25 which sensed whether any DC current was flowing from the charger, and, if there wasn’t, turned the current off at the wall outlet. Using the above example, it would take 100 years to pay for itself, and it would use electricity itself, resulting in either a draw or even a loss.
In conclusion, something left “on” all the time drawing less than a watt a month isn’t a major concern. It would add about.07¢ to your electric bill. Having said that, there are plenty of items that, even when they are turned off, will draw 5-10 watts or more, and these ones can add up. Over the course of a month, a persistent 15-watt load will add about $1 to your monthly electric bill. To save energy, you should look at these items first.
The Kill-A-Watt, for $18 at newegg.com, is much more useful (and less expensive) than an infrared camera. In general, it makes sense to attack persistent loads draining over 5 watts and ignore anything less than 1 watt. I know that every little bit counts, but it’s more efficient to go after the big offenders – and you might be surprised to know which ones they are! My very expensive Bose Wave clock radio draws 10 watts continuously, whether it’s playing music or not. On the other hand, my “el cheapo” clock radios, performing the same function, draw less than 1 watt.
I highly recommend all homeowners get a Kill-A-Watt. They are very valuable in discovering where your electricity is being wasted or not wasted, whichever the case may be.
The smart outlet of the future will be connected to a smart grid. This grid will monitor use and charging, so that appliances can actually store electricity and act as their own back-up power source. Stay tuned for more on this topic, and check out EV Authority for more battery-related news.
