Volts vs Joules

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.


Recommended Voltage

on Fence Line


5,000 Volts


5,000-10,000 Volts


5,000-10,000 Volts


5,000 Volts


5,000-10,0000 Volts


5,000-10,000 Volts


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- Poli-wire, 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 multi-strand 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.


Output Joules

Stored Joules

Open Circuit Voltage

500 Ohm Load



1.5 J

2.14 J

9,100 V

5,000 V


3 J

4.28 J

10,000 V

5,600 V


6 J

8.57 J

10,000 V

6,000 V

Many manufactures rate their energizers. A unit which is rated as a fifty-mile 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.

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  1. Kori
    Posted May 19, 2016 at 5:51 pm | Permalink

    I raise boer goats and am having trouble containing them. I run woven wire as primary fence with 2 hot wires 1 on top and 1 on bottom( about 10 to 12 in off ground). I also have about a 70 to 80 yards of 3 strand just electric fence along the driveway.

    1st yr we ran everything off a solor zahbra sp? Solor charger with 1 ground. Seemed to work OK towards end of grazing seasons it lost charge.

    2nd year we split lines into 2 padlocks (removed connecting wire from old fence line to new fence line). I replaced old charger with another zahbra solor charger for old line. The new line I used a 25 mile plug in model with a 4′ t post as my ground. Goats are still getting out.

    New lines has the 3 strand plus 1 bottom where it is woven. Thanks in advance

    • Lacy Weimer Lacy Weimer
      Posted May 23, 2016 at 1:46 pm | Permalink

      I would start by testing the chargers directly at the positive terminal, without the fence attached. Use a fence voltmeter to do the testing. If you are not getting adequate voltages from chargers they may need repaired. If voltage readings are good, check for shorts on the fence line. How deep are the T-posts you are using for ground rods in the ground?

  2. Leslie
    Posted March 5, 2016 at 7:01 pm | Permalink

    We have kinko goats they walk through the electric fence like it’s not there. Should we move up to a 6 joules or higher or to a woven wire fence?

    • Lacy Weimer Lacy Weimer
      Posted March 9, 2016 at 1:07 pm | Permalink

      What is the voltage on your fence line and do you have a good ground bed? Is the ground frozen? If the ground is frozen the Kinko may not be making a good ground. Without a ground there will not be a shock.

      • Leslie
        Posted March 10, 2016 at 4:39 pm | Permalink

        We have installed a 6 joules charger on a 1 bare
        Metal line, 3rd line down (the other lines aren’t
        Connected.to the charger). Its a 100 miles one
        On apx. 1/2 mile of fencing. Good ground wire.
        Still at least 3 are getting out – maby more.Any

        • Lacy Weimer Lacy Weimer
          Posted March 11, 2016 at 9:42 am | Permalink

          Have you tested the voltage on the fence? A fence tester is a must have on the farm. What species are you containing with in the fence? It is important to have at least 18′ of ground rod with the 6 joule unit. I would recommend at least (3) 5′-6′ ground rods spaced 10′ apart. Without a properly working ground bed, the animals may not be receiving the full shock.

          • Lacy Weimer Lacy Weimer
            Posted March 11, 2016 at 9:44 am | Permalink

            Sorry Lesile,
            I forgot you had Kinko goats…if you have great voltage on the fence they may just be cantankerous!

  3. john
    Posted February 25, 2016 at 6:23 pm | Permalink

    I am a little confused so bear with me…
    I have a few bee hives to protect, i am looking at a 1 – 1.5 joule unit and want to hook this up to a 12v deep cycle and that to a solar panel. My concerns are I do not understand:
    1. the amp draw from the fencer and therefore the size of solar panel I will need ..
    2. what the voltage will actually be on the line when it states 9k open circuit and 2450 with 500ohm?
    the size of the area to be protected is very small as there are only 3 hives so I am not looking at miles of wire etc…
    I would appreciate any advise or insights thanks.

    • Lacy Weimer Lacy Weimer
      Posted March 2, 2016 at 10:45 am | Permalink

      A 1-1.5 joule unit is plenty big enough to use around your hives.
      To sufficiently keep the battery for this unit charged I would recommend a 20-30 Watt panel.
      As long as the fence is built properly and the line is kept free of weeds and debris you should read voltages between 6-8 KV.
      Check out solar panels and solar charger controllers here.

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