The Shield is designed to protect an entire home from lightning, solar flare (coronal mass ejection), power surges, and an electromagnetic pulse. Our family of technologies have been tested at Keystone Compliance, in accordance with all military standards
Here abouts the power company mounts similar at the service entrance weather head. While I think they could be useful, a powerful EMP or lightning strike would - it seems to me - overwhelm such a small device. I am skeptical.
There is actually a lightning arrester built into the electric meter/base, whereby the extreme voltage of a lightning strike will jump a small air gap between a metal piece tied to the hot wire and the grounded enclosure of the meter. Crude, but mostly effective.
Lightning arresters are also out on the lines, spaced occasionally, to perform the same function. And, near substation transformers, there is usually a set of lightning arresters that serve to protect the transformer from transient over-voltage. I don't know how effective they'd be against an EMP - I suppose, it depends on how powerful the EMP is.