I bought one several years ago advertised to cover 150 miles of moderetly weeds fence with a 12 joule output at 8,000 volts - - - I have 5 miles of fence

Going to the south farm with one ground I was down to 5,000 V so I put in another 10' steel copper clad ground rod 10' from the first - - - up to 6,000 volts on the south farm - - - another 10' copper clad rod and I get 7,500 on the far farm.

After the cattle got used to this I have unpluged the noisy thing when working in the shop and forgotten it for a couple of weeks and they still don't check it.

My middle groung rod is under the downspout of the work shop and I feel that helps

I also paid extra for a lighting arrester and that charger is probably over 20 years old and going strong.

Buy the biggest one you can afford and depending on the depth of the water table make sure the ground rods are long enough - - - in the soil around east central Indiana a galvanised rod will be gone in 3 to 5 years but the copper clad will last several decades - - - that is why the power companies use them.

Galvanised might work in your area but check with the power company and find out what they use and or reccomend