An electromagnetic pulse is the least likely threat in our library and one of the hardest to recover from. Protection is layered, and much of it is simple.
What an EMP is
A high-altitude nuclear detonation produces an electromagnetic pulse in three parts. CISA describes them this way:
- E1 arrives in about a nanosecond to a microsecond, with a standard peak field of 50 kilovolts per meter. Wires and cables act as antennas and carry the surge into electronics.
- E2 follows over microseconds to a second and resembles lightning; protection against E1 generally covers it.
- E3 lasts up to hundreds of seconds and drives currents through long power lines, the same mechanism a severe geomagnetic storm uses to threaten large transformers.
Read our threat guide to solar storms and EMP for the history.
What the commissions found
The congressional EMP Commission tested equipment against simulated pulses and reported in 2008 that every system tested failed when exposed. It noted that emergency generators generally carry fuel for less than 72 hours. In its 2017 report the Commission judged that a nationwide blackout could plausibly last a year or longer. Other government assessments have disagreed about the likelihood, so we treat EMP as low-probability and high-consequence, and design so the estate keeps working either way.
For geomagnetic storms, grid operators now plan to a federal reliability standard, NERC TPL-007, which sets a benchmark storm and requires assessments of large transformers. That protects the bulk grid over time; it does not protect your home.
Four levels of protection
CISA's 2019 guidelines describe four levels of protection, which map well to a private estate:
- Level 1: unplug what you can, use lightning-rated surge protection, and keep spare critical electronics in Faraday containers.
- Level 2: EMP-rated surge protection, double-conversion uninterruptible power supplies and fiber-optic links instead of copper where possible.
- Level 3: shielded rooms with at least 30 decibels of attenuation.
- Level 4: at least 80 decibels of shielding, double-door entries and military-standard construction.
CISA estimates that Level 3 often costs well under 1 percent of the protected system's cost and Level 4 about 1 to 5 percent when it is planned at construction. That is the strongest argument for designing protection in from the start rather than adding it later.
How we design for it
On a Styrkholm estate, the power room and communications sit inside shielded space, the service entrance and critical circuits carry surge protection, and spare inverter controls, charge controllers, radios and well-pump controllers are stored in shielded enclosures. Just as important, every essential system has a version that needs no electronics at all: a mechanical well pump, wood or masonry heat, gravity water from the cistern, manual valves and paper procedures.
Key takeaways
- E1 damages electronics in nanoseconds; E3 threatens the grid and its transformers.
- The EMP Commission judged that a prolonged blackout could plausibly last a year or longer.
- CISA sets four protection levels, from Faraday containers to fully shielded rooms.
- Mechanical backups for water and heat matter as much as shielding.
This guide is general information to help you plan. It is not engineering, legal or water-rights advice, and requirements vary by state and county. Every Styrkholm project is designed by licensed professionals for the specific site.