When determining the electrical needs of your fence system it is important to recognize the difference between volts and joules. A volt is a unit of measure assigned to the electrical potential or voltage across a conductor. However a joule is a unit of energy or work done, to move an electric charge through an electric potential. The following are mathematical understandings of volts and joules, which later will be put into layman’s terms according to choosing the correct energizer.
The difference between volts and joules can be simplified by remembering that joules are the energy used to create voltage on the fence line. Whereas, voltage is the speed at which the current is moving along the line. The diagram below is an excellent example of volts and joules.
Joule = Truck
Hill = Fence
Speed = Voltage
Weight = Ohms/Weed load/Resistance
When selecting a truck to haul livestock, you must first determine the heaviest load that the truck will need to pull. The truck must be capable of pulling the trailer and stock successfully. Choosing the appropriate energizer for your fence system is a very similar concept. Consider that the voltage is carried by the speed at which the charge travels through the fence line and joules will be created by the energizer according to the watts per second of output. In an electric fence system, a high voltage is important for making sure that an electrical charge can find its way through the hair on the animals it is intended to contain or exclude. The more or thicker the hair, the greater the voltage required. The higher the voltage, the greater the charged wire’s ability is to shock the animal that happens to touch the wire. The longer the fence line (mileage) and the heavier the weed load or resistance on the fence, the more output joules the energizer will need to maintain a volt range between 5,000 and 10,000 volts for good stock control.
Animal 
Recommended Voltage on Fence Line 
Horses 
5,000 Volts 
Cattle 
5,00010,000 Volts 
Sheep/Goats 
5,00010,000 Volts 
Pigs 
5,000 Volts 
Predators 
5,00010,0000 Volts 
Deer 
5,00010,000 Volts 
Pets 
3,000 Volts 
“It is always best to take the path of least resistance.” This is exactly what to keep in mind when building and choosing an energizer for your fence system. Resistance will decrease voltage on your fence line, because each energizer only has a specified amount of output joules (energy) to maintain the voltage along the conductor (fence line). When resistance begins to diminish output joules the voltage falls low enough that it becomes ineffective because it cannot bridge or arc across the insulation of the hair and hide of the animal. The following are common causes of resistance:

Weed Load

Induction Stray voltage bridging to neutral wires, gates, diagonal braces wires, etc.

Bad Connections

Multiple Splices

Broken Insulators

Type of wire Poliwire, Tape, Ribbon, High Tensile, etc.

Rusty Wire
Generally rule of thumb is a minimum of 1 joule of output per mile of fence, to maintain a secure voltage. Kencove is willing to step outside the box and state, “This is not enough power once you do the math!” A mile is equal to 5,280 feet, which in turn is equal to the perimeter of 40 acres. Would you want a 1 joule unit to power your multistrand 40 acre paddock? The easy answer is “NO”. Kencove would recommend at least a 6 joule unit with an open circuit voltage of 9,500 volts. Understand that if your fence line has numerous sources of voltage leakage, you will need to choose an energizer with a higher joule rating. The truth of the matter is that you can never have too much power. When training livestock having too little power is no different than having no power at all and the fence could actually causes harm to the animal.
Commonly energizer manufactures and dealers overestimate the amount of fence an energizer will securely power. In today’s world it is easy to fall for attractive ads and eye appealing packaging, so when purchasing an energizer look closely at the details.
Item 
Output Joules 
Stored Joules 
Open Circuit Voltage 
500 Ohm Load (Resistance) 
EK1 
1.5 J 
2.14 J 
9,100 V 
5,000 V 
EK3 
3 J 
4.28 J 
10,000 V 
5,600 V 
EK6 
6 J 
8.57 J 
10,000 V 
6,000 V 
Many manufactures rate their energizers. A unit which is rated as a fiftymile unit only means that it can essential power 50 miles of a weed free, well insulated, single strand wire. You will be disappointed if you select an energizer based on miles of fence line. Ultimately, the output joules of the energizer should be the selling point. If only stored joule information is available, you can estimate that output joules are about 70% of the joules stored within the units capacitors.
Remember, that the energizer is the heart of your fence system. It should be accurately sized according to what type of animals are being contained or excluded, the length of the fence line, and how long it could potential be in the future, as well as possible resistance on the fence. This is a basic description of the relationship between volts and joules, and the effectiveness of your electric fence. Kencove hopes that through your comments and input the readers of this Blog will be able to have greater insight into the proper energizer for their fence.
4 Comments
After I installed my diagonal figure eight braces for my end posts, some of my hot wires are touching the brace wires. How can I keep them apart? Is there a product I should use or should I redo my diagonal brace wires? Any help you can provide will be appreciated!
Ken
The most frequent solution is a short tube insulator (item code I50). But because your brace is already built, you could pull the diagonal wires together by wrapping with hightensile wire or install a split bolt. Using coated wire for the diagonal would also solve this problem. Another way to avoid the hot wires touching is using insulator tubing with a Quik Brace. You can see that product & video here: http://www.kencove.com/fence/Quik+Braces_detail_HQBS12.php
Great useful information. Does more Joules mean that the current can power through problem areas such as snow on lines etc.?
Yes, as long as you purchase a larger joule charger than what is needed for the perimeter footage. This will help the voltage to push past the weed or snow load. The rule is one joule per perimeter mile of fence.