The SolarGuard 150 Solar Fence Energizer is fully portable with an all-in-one compact design. The energy-efficient solar panel charges the internal battery to power the fence line for reliable, year-round performance. With 0.15 output joules, it powers up to 10 miles or 40 acres of fence. This low-impedance energizer has a highly visible, flashing red light that indicates the energizer is working and powering the fence. Battery-saving mode maximizes battery life. Can be mounted to t-posts or wood posts. Internal 12-volt battery included. Capable of operating up to 21 days without sunlight. BEFORE USE, connect the battery, and charge for 3 days in sunlight.