http://files.dnr.state.mn.us/assistance/backyard/privatelandsprogram/beehive_protection_with_electric_fence.pdf
You want an energizer that is 12 volt and puts out at least 2 joules of power.
Here are a couple energizers:
I own a fencer from Premier1. They do not make my style anymore. I put the fencer and battery inside a beehive and mounted a solar panel to the telescoping cover.
From Premier1 out of Iowa. They do sell very good quality fencing supplies. With various levels of quality. https://www.premier1supplies.com/c/fencing/
Patriot Fencer 12 volt can put out 3 joules
https://www.premier1supplies.com/detail.php?prod_id=34988&cat_id=0&
You will need their wiring harness and a deep cycle battery. One of their solar panels can be added to charge the battery. The folks at premier1 are very helpful. Do not buy the netting. Weeds can grow into the netting and the netting tears easily. With the fencer, solar panel and battery you can have a $400.00 investment.
From Fleet Farm:
$269.00 puts out 3 joules. I own one of these.
http://www.fleetfarm.com/detail/parmak-30-mile-12v-solar-battery-fence-charger/0000000205592
This can mount on a t-post. But you need to buy a bracket to mount it on the post.
