Not necessarily — the joule rating of an electric fence energiser can affect its effectiveness, but it isn't the only factor. The key is understanding which joule rating you're looking at and what sort of fence you're powering. The running voltage of an Electric Fence Energiser is more important that the joule rating to determine effectiveness.

The joule rating effectively determines the amount of fencing can be run off a particular energiser.

What do joules actually mean?

Joules measure energy. With electric fence energisers, you'll commonly see two ratings:

• Stored energy (joules): the energy stored inside the energiser before it fires.
• Output energy (joules): the energy actually delivered into the fence under the manufacturer's specified test conditions.

Output joules is the more useful figure when comparing how effectively different energisers can power a fence. This can be affected by the individual electronics within the energiser.

A higher output joule rating generally means the energiser can deliver a stronger pulse and maintain an effective shock when the fence has more wire, vegetation touching it, or other electrical losses.

A 0.45 output Joule rating will do about 3000m of single conductor fencing (even that depends on the conductivity of the conductor) whilst a 7joule energiser will run 30000m of fencing but both will be running at about 6000v, and it is this voltage that actually does the controlling of the target. Voltage hurts, Joules do not. Joules is simply a mathematic equation of watts multiplied by time

However, a higher rating doesn't automatically mean a better fence. Earthing, wire quality, fence length and vegetation can each make a huge difference.

What matters besides joules?

• Voltage under load: the voltage remaining when the fence is actually doing its job. A high unloaded voltage can be misleading.
• Earthing: poor earthing can dramatically weaken the shock, even with a powerful energiser.
• Vegetation: grass and weeds touching the wire drain energy.
• Wire and fence length: long runs, poor connections and unsuitable conductors can reduce performance.
• Animal type: thick wool, for example, can make sheep harder to deter than short-haired animals.

A fence tester is the best way to check actual performance at the energiser and at the furthest point of the fence.