Choosing an Energizer for Your Electric Fence
We hate to keep mentioning the local farm stores in a bad way, (and if you have a good one, by all means patronize them) but most of the farm store counter guys you talk to will probably not know the difference between a hog jowl and a fence joule. Before you buy, you should probably understand something about a joule. A joule is a hard thing to understand, but basically it is an electronic measurement of 1 watt for 1 second. That probably tells you nothing – we don’t know either. But, you need joules to push the pulse down the fence wire. The more joules, the more power. The shape or length of pulse time also has a bearing and a high powered, low impedance, short pulse will travel through much more resistance (vegetation & fence load). Anyway, the point here: some energizer packaging will state the amount of wire or acreage their unit will power. Don’t believe it! Others will only state the output joules or only the stored joules. Make sure you are comparing apples to apples and not one’s stored joules against another’s output. At the very least, drop their claim in half. We feel that the best way to size an energizer is to find out the output joules and figure that 1 joule will power between 3 to 5 miles of wire. If they can’t give you the output joule rating, then don’t buy it.
Choosing an Energizer
New Zealanders have said that we Americans usually overbuild the fence, then under power it! That’s probably true. The worst thing you can do if you are just beginning with electric fencing is to build a beautiful fence then not have enough power on it. Normally, in round numbers, we would say that 3500 volts will keep cattle in or 6000 volts will keep goats in. However, you have to compensate for the May-June fence load and the August drought. When vegetation and wet lush grass invade your fence wire, you need enough power to compensate and keep it browned down. If you have a system that puts out 9,000 volts and it drops down to 6000 in June, you are in good shape. However, if you drop from 5000 to 2000, you have a problem.
We look at the output joule rating on an energizer and estimate that 1 output joule will power about 3 to 5 miles of wire. For example, if you have 15 miles of fence (15 divided by 3 = 5), you will need an energizer with a minimum of 5 output joules. If you will be expecting heavy vegetation loads or plan to add more fence later, we would suggest that you buy in the 8-12 output joule range. Surplus Power is comforting. Just make sure when you are shopping that you compare apples to apples and not output joules to stored joules. We have high confidence in the New Zealand brands of energizers. They are proven to be good performers and usually last a long time.