Although solar energisers sound like the “cheapest” way to electrify a fence, they are quite costly.

Let’s figure the average cost for running a 2-joule energizer for 10 years using both an 220 volt mains energizer and the same solar-powered unit. (The Trapper AN24 may be used in either format.)

The power consumption of most energisers for agricultural / livestock control purposes will range from 1 watt up to 25+ watts - depending on the model. Operating a 2.5 watt energiser (the Trapper AN24) continuously for 24 hours per day for 30 days at a utility company charge of 23 pence per kilowatt-hour (includes daily standing charge plus unit cost) will equal;-

2.5 watts x 24 hours per day x 30 days / 1000 = 1.8 kilowatt-hours (kWh)

1.8 kWh x 23 pence = 41.4 pence/30days

So - £0.414 is the cost of operating the 2.5 watt energiser for 30 days at this rate, or a cost of £4.96 per year.

Although free energy supplied by a solar panel sounds enticing, the reality of a solar setup is very pricey. Not only do you need to buy the energiser, you need to purchase the battery, solar panel and stand. As with all things, the more parts you have, the more likely something is to break or go wrong. Panels themselves are made of glass and need to be protected from breakages. Solar energisers are ideal for spaces of fence where AC energisers are not an option, or for portable electric netting or rotational grazing. Even though free power sounds like the most cost-effective option, this is not always the case.

Where Solar power comes into its own is where mains is not suitable. Here the only option is to use a battery. The same 85aH battery with the same energiser will need re-charging every 3 weeks using a 12 hour charge. The constant total depletion of the battery charge will also effect and reduce the life of the battery with the charging at irregular intervals. Using a solar panel will maintain a charge regularly throughout the year and in average-plus days will take over the running of the fence completely as well as topping up the battery.