Electric Fence Charger Calculator
Determine required energizer output joules and voltage ratings based on perimeter length, wire strands, and vegetation weed load.
Recommended Tools & Equipment
Tested hardware and components for high reliability
How Electric Fence Energizers Are Sized
An electric fence is an open electrical circuit. When an animal contacts the wire, electrons flow through the animal's body into the soil, back through the copper ground rods, and into the charger to complete the circuit.
Output Joules vs Stored Joules: Stored joules measure the electrical energy inside the charger's capacitors; Output Joules measure the actual shocking energy delivered down the wire into the weed load (typically 70% of stored rating).
Required Ground Rods = 1 eight-foot copper rod per 1 to 2 Joules of energizer capacity.
Frequently Asked Questions
Why do sheep need a higher voltage than horses?
Sheep possess thick, dry wool which acts as an electrical insulator. A minimum of 4,500V to 5,000V is required to arc through wool lanolin to reach nerve endings.
What causes electric fence voltage to drop?
Over 80% of low-voltage problems trace to inadequate grounding (short rods in dry gravel) or wet green weeds touching the bottom wire and bleeding current to ground.
Can an electric fence charger be too powerful?
For livestock, an overpowered charger will not physically harm animals because pulses are brief (less than 3/10,000ths of a second). Extra joules ensure the fence remains hot even in heavy overgrown brush.