Electric Fence Essentials: The Importance of Energisers

An electric fence energiser, by definition, is a device that controls the electrical pulse sent down an electric fence. It uses a power source that is either a battery or mains 240v power. Most often a pulse is sent down the fence every 1.5 seconds. However, there are some models of energisers that allow you to choose the timing of the pulse yourself. They are also referred to as fence chargers, fencers, or fencing/power units.

Generally, an electric fence consists of an open electrical circuit comprising of two arms. The first arm is the fence itself, connected to the power terminal of the energiser. This part of the fence has to be completely insulated from other conductive material (ground, leaves, grass, metal or brick) by plastic insulators or an air gap that is at least 3 cm wide.

The second arm is the ground which is connected to the earth terminal of the energiser. This structure leaves an open electrical circuit that will close as soon as an animal comes close enough to the fence. Once the animal touches both the physical and the ground part of the fence, the electrical circuit is closed and electricity flows from the fence down to the ground through the animal and goes back to the energiser via the earth terminal giving the animal a shock as it touches the wire.

Next, it is important that you choose the right electric fence energiser. First of all, think about what type of animal is being controlled? Sheep and poultry, for instance, have good insulation provided by wool and feathers. For these, it is better to you use a higher voltage rating energiser. Contrary to this, pigs, horses and dogs are more easily controlled, so a lower voltage will do the trick. Finally, let’s go through some of the ratings applied to energisers so that you can be properly informed when looking through the different models.

Stored Energy

electric fence energiser

The electronic circuitry takes electrical energy from the power source of the fence and accumulates it in the storage capacitors. This is the stored energy but not necessarily completely available to the fence. This stored electricity is measured in joules – the closer this figure is to the output energy figure, the more advanced the electronics in the energiser and fence.

Output Energy

electric fence energiser


The above-mentioned stored energy is discharged through an output transformer to the energiser’s terminals. Part of that energy is lost in the process, so output energy is always lower when compared to stored energy. Simply put, the output energy is the effective energy that is actually applied to the fence, and this is the one you use to compare how strong different types of energisers are. Still, as already stated, the lesser the difference between stored and output energy figures – the stronger the capacity.

9/12 Volt Energisers

9-volt energisers are portable, light-weight, easy to handle types of energisers. These are usually battery-powered, and the advances in this field of technology have led to batteries with long life-spans. A 9-volt energiser would be an ideal option for equestrian yards. The 12-volt energisers are more powerful when compared to 9-volt ones. These function with rechargeable batteries or you can opt to power them by using mains 240v power.