"More and more people are incorporating solar panels into their fence systems, generating a local source of energy and eliminating the need to recharge the batteries."
One of the biggest problems facing users of electric fencing is that the power unit (the energiser) is often a long way from a mains power supply. As a result, users have to rely on heavy 12V deep cycle batteries which have to be moved once every few weeks to be charged. Given that a typical battery can weight between 15 and 30Kg, carrying one across a field is not a great prospect.
Some modern fence units are factory fitted with a small solar panel, but they are easy to retrofit to an existing fence system:
First calculate the amount of power that the fence energiser consumes in a day, by multiplying the current draw (in amps or milli-amps) by 24 and then multiplying that by 12 to get the power consumption in watt-hours (Wh). To ensure that the solar panel produces enough energy all year round, we use a calculation of 70% energy production for 5-hours a day. Starting with your 'Wh' number, divide this by 0.7 and then divide the result by 5. The result will be the minimum solar panel size you need.