How an Electric Fence Works

An electric fence works by sending short pulses of electricity to a network of conductive fencing.

These pulses, which are generated by an electric fence energiser, are generated regularly and continuously. The pulses are high voltage but very low current.

The pulses are uncomfortable to animals but they are not dangerous or damaging and pose no lasting threat to animals or animal keepers, so animals simply learn to avoid them and keepers generally set them up before connecting a power supply.

The energiser connects to the earth using a metal stake in the ground and when an animal touches the fence, because it is stood on the ground, it completes the circuit.

A typical electric fence is made up of the following main components:

The Energiser

An energiser is a small box which takes a power supply, typically from a 12v battery, solar panel or mains electricity, and generates a short electrical pulse at regular intervals, roughly every one to two seconds.

Most energisers have a visual indicator such as a flashing light to show you they are working.

A battery powered energiser is best for installations that need to be moved regularly, such as strip grazing, field rotation, or for areas which are not being consistently grazed. Battery energisers are also ideal for areas which do not have easy access to mains electricity or where solar powered energisers may not experience much sunlight such as valleys or wooded areas.

Most energisers feature weatherproofing of some description, allowing them to be used in all conditions. It is important to note that in cold conditions, batteries do not last as long and will require more regular charging.

The Fence / Fence Wire

The fence wire is the means by which the pulse is conducted around the perimeter of the area you are trying to enclose or protect.

There are a variety of fence wire options available and the type you choose for installation will be determined by a number of factors.

Solid Galvanised Wire

Many common agricultural fencing installations are made with wooden posts and galvanised wire.

Galvanised wire offers excellent conductive characteristics and can easily be energised for hundreds or even thousands of meters.

The wooden posts offer good isolation in dry conditions but could allow the pulse to earth prematurely in wet weather if the post is saturated by the weather.

This method of fencing can be cost effective as it can negate the need for any additional fencing.

Steel Stranded Nylon Rope / Wire

Steel stranded nylon rope or wire, often referred to as "poly wire", is a very common material used for electric fencing mainly due to its ease of use and low cost.

The main bulk of the rope is a plastic twine which lasts a long time and does not rot. This is woven with multiple strands of stainless steel which act as conductors for the electricity.

Poly wire needs to be suspended on posts or threaded through isolators for the best results.

Steel Stranded Nylon Tape

Steel stranded nylon tape, like wire, is a very common material used for electric fencing mainly due to its ease of use and low cost.

The tape is a woven nylon gauze-like material which includes multiple strands of stainless steel to conduct the electricity.

Tape has the added benefit of having a larger surface area to encourage a greater contact patch with the animal touching it, and thus leads to a more effective conduction.

Due to its larger surface area, tape is easier to see.

Poly tape needs to be suspended on posts or threaded through isolators for the best results.

The Earth Connection

This final piece of the electric fence puzzle is what earths the current and closes the circuit.

This is typically created with a length of conductive material inserted in the ground and connected by wire to the energiser.

It is this same unpleasant sensation which deters predators and other pests and keeps them OUTSIDE of the fenced area.