Acres vs. Miles & Routing Power on an Electric Fence

There has always been and probably always will be discussions involving recommendations for the size of an energizer that one should use on your electric fence.  I don’t know that I have ever personally won any of these discussions, but I haven’t lost too many either.

Most manufacturers or electric fence gurus make recommendations based on either acreage or miles of fence. Most relate these recommendations based on joules but actually a few manufacturers state that joules are not important at all. It can be, and usually is a confusing proposition to decide who is right.

I, myself, have been working with electric fencing for over 25 years and I still honestly can’t give you a definitive unquestionable answer. I can only state what works for me and why. There really is NO international standard that would settle any discussions based upon pure documented fact, or none that I have found (for more information on this topic, see a previous article about how to choose an energizer).

But, what I want to talk about on this blog is how to route the power around an electric fence system, from point A to point B. First, let’s look at some of the standard recommendations and you can draw your own conclusions.

Those that talk about basing your energizer to acreage usually have a ratio of 1 output joule will supply enough power for approximately 25 acres. And those that talk about miles of fence usually have a ratio of 1 output joule will power approximately 3 miles of fence. Manufacturers usually suggest a ratio of 1 joule to 10 miles of fence, which I feel is highly exaggerated.  There are a lot of differences in all of those scenarios.

To me, the acreage suggestion does not take into account how intense your fencing is or how many cross fences there are. There could be one cross fence or these 25 acres could be divided up into a dozen 2 acre paddocks.  That would relate to significantly more total length of fence and the result would be that you might be underpowered if you had gone with the acreage recommendation.

Personally, I feel that determining your power requirements to actual distance of fence will get you a better value to work with. Although it is true that most farmers know their acreage better than they do the distance of fence perimeters – you are going to need to come up with a pretty close estimate of the lengths of fence before you order any materials anyway. Otherwise, you wouldn’t know how many rolls of wire or fence post you will need.  So, you will have a good number to work with.

Another question that usually comes up:  If you have 3 strands of wire that is 1 mile long, do you need to compute this as 1 or 3 miles of fence? Well, that depends on how you hook up your jumper wires and route your power and this is the point of this blog article.

Routing Power for Electric Fence

Drawing 1

Drawing 1. Let’s look at the drawing above and consider that this is a 1 mile long section of fence. If you hook up your jumper wires as shown, then this will relate to one mile of fence. This is what is considered a loop design and probably the “textbook” design. It creates a, so to speak, grid. By installing both jumper wires A & B, the pulse will actually be flowing both ways on the fence wire. This is similar to the way that a rural electric company routes power around the countryside. Power is supplied from both directions. If there is a break or a fault, then you would still have power coming in from the other direction. This is the way that many people route their jumper wires and it works fine and you probably get more power on the system. This hook up will be allowing for less resistance in your system. I, personally do NOT do this for the simple reason that if and when you do have a short, it is very hard to find the short with a meter. The readings you take will literally walk you to death!

Routing Power for Electric Fence

Drawing 2

Drawing # 2 (above) The design above would also be considered as 1 mile of fence and this is the way, in which, I route generally route my power. I install jumper wires A at the beginning section of each fence leg, but I do not install the jumper wires B as are shown in drawing #1. The lower wires are dead ended at the finish of the fence leg. I consider my top wire as my transmission wire and this is consistent around my entire perimeter as well as any multi-strand cross fences. The reason that I do this is that it is much easier to find any problems or shorts in the future. With the hook up above in Drawing # 2, each wire on this section will be isolated. If you take a meter reading on each wire on the leading end, by jumper wires A, you will detect any short on wires #2 or #3.

Routing Power for Electric Fence

Drawing 3

Drawing 3. If you hook up your jumper wires as shown in Drawing #3 above, then this will compute to 3 miles of fence rather than the 1 mile as in the other two hook ups. Here the power flows down wire #1, is then transferred to wire #2 with the pulse flowing back, then it is jumped onto wire #3 and eventually onto the next section of fence. I do not recommend this way and don’t see any benefit to it. It will require more power to run it.

Voltage: In the design of Drawing #1, which has everything looped together you will probably have a consistent voltage reading around your entire system.  In Drawings #2 and #3 you will most likely have a higher voltage reading at the end of the system then you do at the beginning of the system. My layman explaination of this is that where you have all these dead ends – the pulse does not just disappear – it reaches the end, then so to speak bounces back up the wire. This is also referred to as feedback, but the result will be higher voltage readings at the end of the system. This doesnt happen on the looped system because there is no end.

Jumper wires: I generally use the coated insulated wire for my jumper and lead out wires. Although this is not completely necessary, it is easier to work with. It bends and holds its shape quite well and in the cases where these jumpers protrude out, I am less likely to accidently bump into one of them and get a shock while working on fence.

I think that in summary, I would suggest that you make your choice and do it consistently through-out your entire system. It is critical that you know how the jumper wires were installed and which direction the pulse is flowing down each hot wire. Again, consistency and a good understanding of where the power is flowing will aid you – when it comes time to find a short that is sucking power out of your system.

Maintenance is a part of keeping all fences in good functional shape, no matter whether it is barbed wire, woven wire or electric fence. If you design it and understand it – the maintenance time over the next 20 to 30 years will naturally be much less. And lastly, if you utilize insulated or non-conductive PasturePro Line Posts, you will also be reducing your maintenance issues!


About Gary Duncan

Gary has been active in the fence business for over 15 years. He also raises Highland cattle in a management intensive grazing system and was the first person to market the PasturePro post back in 2005. He enjoys discussing all things grazing and is the main contributor to the blog.
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