The military EMP devices (although are also man-made), are build to serve a whole different purpose. They are highly advanced tactical weapons meant for combat. They are non-lethal, but they debilitate the enemy’s combat capacity by rendering useless everything that uses or runs on electrical currents.
In just the last twelve months Congressional members and top level administrators at the Department of Homeland Security have warned of threats to the national power grid so serious that should they occur life in America as we have come to know it would change almost instantly.
Former DHS head Janet Napolitano, in a letter to her successor