Good background on the magnetic multi-pulse class e2 EMP weapon that has allegedly been neutralized or seized by Q Team:
http:// www.futurescience.com/emp/E1-E2-E3.html
The E2 pulse in itself is probably not a threat so much in itself, but if it is preceded by an E1 pulse, there would be a large threat to consumer electronics and possibly also power transformers.
The group that allegedly took control of the Black Hats' EMP weapon was the NNSA/OST: National Nuclear Security Administration / Office of Secure Transportation. That office belongs to the Dept of Energy, not No Such Agency as the NNSA initials sort of resemble.