I have 40 acres divided up in five acre paddocks, about twelve thousand feet of wire. Had a Gallager S50 with 1.5 joules of power, and paid near$300 dollars for it. Worked great until the grass started touching the fence, then lost too much power and ended up with three chargers on it. This year I bought a Taylor made Brute charger with 6 joules for $399. Have about 7500 volts on the fence right now, so I think maybe it'll be ok. Still some grass to grow up on it. Just watch the price and the joules you get for your money. You can always expand your fence with enough charger, but you can't make the charger do more output. Right now I have a car battery on it, and change it every two weeks. The solar panel for it was another 400 dollars, and I'll get it next year if I'm satisfied with the performance. gs