Quote:
Originally Posted by Mark Rozitis
1. Unplug chargers (think cell phones and iPods) when not in use. Only 5% of the power drawn by a cell phone charger is used to charge the phone. The other 95% is wasted when it is left plugged into the wall.
|
Not exactly. When the output of a transformer has a high impedance (i.e., it's not connected or drawing any current) the input also sees that high impedance, effectively becoming an open circuit.
You can try this with a Kill-o-watt device, or (if you are supremely careful) with a digital ammeter. Charging, the current is a few milliamps; idle the current falls to the microampere level. 100 uA*120V=.012 Watt, or just over 1 kWh per
decade. At 14 cents a kWh, the savings isn't too much.
That doesn't invalidate the idea of unplugging things you don't need to use: A pancil sharpener I have draws 40 mA when idle, do the math on that one!