It depends on your companies policies and if you are part of the electrical union, the IBEW. Most IBEW locals do require a yearly drug test. Some non-union companies require it as well, as many can get lower insurance premiums if they routinely drug test their employees for safety. Even if your company does not drug test, they may have job sites that do require them for either similar insurance reasons or because it is a government / city contract that requires it. Drug tests are also routine after a safety incident that caused harm.