Smart phones and tablets are very energy efficient because they are designed to run on a battery for a long period of time. Phones use approximately 2 to 6 watts when charging, while a charger left plugged in without a phone will consume 0.1 to 0.5 of a watt. Charging an iphone or android phone under normal use conditions will typically cost 1 Pound for a full year
See the energy consumption of a phone charger using 5 Watts for 3 hours a day @ £0.19 per kWh.
Cost Per Hour: £0.0009
Cost Per Day: £0.0029
Cost Per Month: £0.09
Cost Per Year: £1.04
kWh Per Day: 0.01
Tip: leaving a device on charge over night could shorten the life of its battery. Try and charge the phone before you go to sleep and then top it up the next morning while getting ready. Turn off all chargers when not in use. This is a good way of saving a little bit of money.