All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
This is forbidden since the Electricity Company is a public or private property and benefitting from the electric current should be done through legitimate means since using other means is simply an act of theft. The evidence on this is that Nawwas bin Sam'an (May Allah be pleased with him) reported: I asked Messenger of Allah (PBUH) about virtue and sin, and he said: "Virtue is noble behaviour, and sin is that which creates doubt and you do not like people to know about it." [Muslim]. One who steals electricity doesn`t like people to know about it because deep down he feels sinful.
On the other hand, a man from the immigrants of the Companions of the Prophet (PBUH) said: I participated in battle three times along with the Prophet (PBUH). I heard him say: "Muslims have common share in three (things): grass, water and fire." {Related by abu Dawoud}. This Hadith doesn`t justify the above illegitimate act.This is because the lawful water intended in the Hadith refers to the water of seas and rivers, not that filled in containers owned by people or companies. As for the word grass, it refers to the grass that exists in the wilderness, not that collected by someone. As for the word fire, it refers to allowing people to benefit from fire through paying for the tools that enable them to do so, and all of these points don`t apply to the issue of electricity. Moreover, it is also worth pointing out that it is forbidden to steal water.
We (Iftaa` Department) recommend circulating these rulings via social media to stop people from depicting falsehood in truth clothing. And Allah The Almighty Knows Best.