Calculate Faraday cage sizing for your devices, get a prioritized protection list, learn what would actually stop working in an EMP event, and see your EMP readiness score out of 100.
An electromagnetic pulse (EMP) — whether from a nuclear detonation, solar flare (Carrington Event), or purpose-built EMP weapon — can disable modern electronic devices across a wide area. A Faraday cage is a metal enclosure that blocks electromagnetic fields, protecting electronics stored inside. This calculator helps you size the right Faraday protection for your device list and gives you an honest readiness score.
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An electromagnetic pulse is a burst of electromagnetic energy that can induce damaging currents in electrical conductors and semiconductor devices. There are three main EMP threat types: nuclear EMP (NEMP) from a high-altitude nuclear detonation, solar coronal mass ejection (CME/Carrington Event), and non-nuclear EMP weapons (NNEMP). Each has different characteristics, but all share the ability to disable unprotected electronics over wide areas.
A Faraday cage works by distributing the electromagnetic energy around the exterior of the enclosure rather than allowing it to pass through to the interior. For a cage to work effectively, it must be made of conductive metal with no large gaps, and items inside must not touch the walls. The cage must also be sealed — gaps around lids or doors are the most common failure points in DIY Faraday protection.
The most important EMP preparation is not Faraday cages — it's redundancy and non-electronic alternatives. A mechanical watch, a manual water pump, a wood stove, a bicycle, paper maps, non-electric hand tools, and seeds are all immune to EMP. The goal is to have a functional life even if all electronics fail permanently. Faraday cages protect the electronic tools that make post-EMP life significantly easier, but they are a supplement to, not a replacement for, fundamental non-electric resilience.
Not necessarily all, and the extent depends heavily on EMP intensity and type. A Carrington-level solar storm primarily affects large infrastructure (power grid transformers, long-distance transmission lines) more than individual consumer electronics. A high-altitude nuclear EMP is more comprehensive and affects a broader range of devices. In either case, devices that are unplugged from the grid and not connected to long antenna-like conductors (power lines, phone lines) have significantly better survival odds. The grid infrastructure itself — especially high-voltage transformers — is the most vulnerable and hardest to replace quickly, which is why even a partial EMP event that spares most consumer electronics could still cause a multi-year recovery.
This is debated among EMP preparedness experts. The consensus for protecting individual devices (not whole buildings) is that grounding is not necessary and may actually be counterproductive for portable Faraday cages — it can create a path for the EMP current to enter the cage. For simple metal containers (ammo cans, trash cans), do NOT ground them. Just ensure a tight seal. Grounding becomes relevant for large permanent installations like whole-building Faraday cages, which require proper engineering.
Solar panels themselves (the photovoltaic cells) are relatively resistant to EMP because they are simple semiconductor devices not connected to large antenna structures. However, the charge controllers, inverters, and wiring connected to solar panels are vulnerable. A practical approach: store a spare charge controller and possibly a small backup inverter in a Faraday cage. If your solar system survives, great. If the controller is damaged, you have a spare. The panels themselves are likely to keep working.
Vehicles manufactured before roughly 1980 that use carburetor engines (no electronic fuel injection) and have no electronic control units (ECUs) are largely EMP-resistant for their core driving function. The ignition system uses points and condenser rather than electronic modules. However, even these vehicles have some electronics — radios, modern alternators, headlights with solid-state components — that could be affected. Post-1980 vehicles with ECUs, electronic ignition, and fuel injection are vulnerable to losing function. Storing a spare ECU and electronic ignition module in a Faraday cage is a reasonable backup for a valued modern vehicle.
The threat is real but the probability is debated. The most credible EMP threat is a large solar coronal mass ejection (CME) — a near-miss occurred in 2012, and the 1989 Quebec blackout and 1859 Carrington Event demonstrate historical precedent. The Congressional EMP Commission has repeatedly warned about infrastructure vulnerability. A nuclear EMP attack requires both a nuclear weapon and delivery capability to high altitude, which limits the realistic threat actors. For most preppers, EMP prep is a lower priority than basic food, water, and power preparedness — but the overlap is significant, and Faraday cage protection for a few critical devices is inexpensive insurance.