Electricity consumption
Some believe that once the phone is not connected, the charger does not consume from the network, does not consume electricity. This is not entirely true. Despite the fact that current just plugged in the charger from the mobile phone is equal to zero, the electricity is still consumed. Just in very small quantities. For comparison: light bulb 40 Watt "cool" these same 40 Watts per hour. Charging the unit per hour winds is only about 50 milliwatts. Even the most frugal and practical people can afford to leave the charger in the outlet round the clock, as monetary savings (energy bill) will be only a couple of cents per month.
Security
In the instructions to the mobile phone and the charger to it clearly States that for security purposes, inoperative for its intended purpose the battery charger must be disconnected from the network. What actually may be the failure to do so? In principle, nothing. Modern chargers for the phone has built-in protection from fire. And burning them is nothing, even if the device is constantly plugged in. But it concerns only high-quality chargers. If the device gets hot even when just plugged in (no phone), preferably its still off. It is possible that ignite and there is nothing but melted plastic can. Especially if it is of poor quality.
What is the risk
A reason to overcome laziness or forgetfulness and yet to always remove the charger from the socket are power surges in the network. For example, if you suddenly cut the power and then turn on again, the AC mains voltage may increase from 220 V to 380 V. all This jump may cause the device unusable or even cause a fire hazard situation.
In summer, the greater danger is the charger left in the socket during a thunderstorm. Then it does not matter whether mobile or not. First, the lightning during the impact can incapacitate any appliance, regardless of what power they consumed current. Secondly, the charger can catch fire after a lightning strike that is dangerous.