Power

The amount of power your smartphone charger waste?

In my view right now I can see six smartphone and tablet chargers. They're all plugged in, and there are no devices attached to them. How much power are they using? Should I unplug them?

Rather than guess, I decided to break out my test gear and do some testing. My test meter of choice for this test is the WattsUp? PRO power meter, as I can use this to measure how much power a device is drawing. While mine is a dedicated test meter, you can pick up domestic power meters from most online and brick-and-mortar electrical retailers these days.
Power is priced in kilowatt hours (KW h, or 1,000W), which is 3.6 million joules of energy. A device rated at 1,000W running for one hour will use 1KW h, while a device rated at 100W will take 10 hours to consume 1KW h.
As for costs, according to data published by the US Energy Information Administration for April 2017, the average cost for 1KW h of electricity in the US hovered around $0.12. The most expensive residential power in the US is found in Hawaii, where it costs $0.30.