Quick Answer
Lightning is the leading cause of electric fence energizer failure. At minimum, install a lightning diverter/choke on both the fence lead-out and the ground lead. Disconnect the energizer during severe electrical storms if possible. A quality lightning arrestor costs $15–$40 and can save a $300–$500 energizer from a single strike.
How Lightning Damages Fence Systems
A lightning strike near a fence line induces a massive voltage surge that travels along the wire at the speed of light. Even a strike 300–500 feet away can generate thousands of volts of transient energy on the fence wire. This surge travels back to the energizer and destroys the solid-state electronics — a common failure mode that most users mistake for simple energizer failure.
The ground system also acts as a pathway for induced current. A strike on a poorly grounded fence can cause current to surge through the soil and up through the ground rods, again reaching the energizer from both directions.
Lightning Protection Components
Lightning diverter (arrestor): A spark-gap device installed between the fence wire and the ground wire, positioned between the fence and the energizer. When surge voltage exceeds a threshold (typically 600–800V), the gap fires and diverts the energy to ground before it reaches the energizer. Cost: $10–$25 per diverter. Install one on each fence lead-out.
Choke coil: A wound coil of wire that slows the rate of voltage rise from a strike, giving the diverter more time to fire. Used in combination with a diverter on the fence lead. Some quality energizers include a built-in choke.
Surge protector (outlet): For AC energizers, use a quality surge protector on the outlet or install a hardwired surge protector in the electrical panel. This protects against grid-borne surges as well as fence-induced ones.
Installation Layout
Mount the lightning diverter on a wood post or insulated bracket close to the energizer but outside the building. The diverter's ground wire should connect to a dedicated ground rod separate from (but within 20 feet of) the fence ground system. Keep the lead wire from the fence to the energizer as short as practical — every foot of unprotected wire is a potential entry point for induced surge current.
Does Disconnecting the Energizer Help?
Yes — disconnecting the fence lead from the energizer during severe thunderstorms provides maximum protection. Many farmers do this routinely during storm season. However, a strike can still damage an unplugged energizer if the fence wire is still connected, since induced current can arc across the open terminals. Disconnect both the AC power and the fence terminal during high-risk storms.
Our Recommendation
Install a Gallagher or Dare lightning diverter ($15–$40) on every fence system. Use a quality surge protector on AC-powered energizers. In high-lightning areas (Florida, Texas, the Great Plains), consider a premium energizer with built-in surge protection (Gallagher M-series, Speedrite 3000+). This $40–$60 investment protects a $200–$500 energizer and avoids the livestock management crisis that follows an unexpected fence failure.