Well, this is interesting as we often have more than one fast-charger plugged in around the house. I had noticed mine are all 'cool' without anything plugged in. So this was a fascinating report to read. They dig down into the approximate costs per year, too. Of course, old chargers maybe a different situation altogether.
Smartphone and laptop chargers use a negligible amount of idle power when left plugged in. Other kinds of chargers vary significantly, however, and it's worth checking their power consumption or just unplugging them to play it safe.
"Measuring such low wattage consumption with consumer devices is tricky, but it’s safe to estimate a power charger with no attached load (no device plugged in and charging) draws between 0.05W to 0.1W or less of power in standby mode. This series of tests conducted by an electrical engineer with more advanced equipment than ours supports our estimate, as he found chargers had a similar range, as does this extensive Department of Energy analysis."
"To put that low level of power consumption in perspective, most LED light bulbs use between 5-7 watts of power. So to even approach the power draw of leaving a single energy-efficient LED light bulb on, you’d need to plug in around 100 cellphone chargers."
See Tested: Should You Unplug Chargers When You’re Not Using Them?
How much energy do your smartphone, laptop, and tablet chargers really use? What about laptop and tool chargers? Should you unplug them when you aren’t using them to save power and money? We measured exactly how much power a variety of common chargers use—and how much keeping them plugged in will cost you each year.