<font color="blue"> I assume the horses dont have access to the power cord. </font color>
These buckets have a plastic 'lid' on the bottom of the bucket where the cord can be stored when heating is not needed. (I actually thought they sent non-heated buckets when I opened the shipping box since there was no cord visible) Plus the cord is covered with a coiled wire. Looks like a spring. I pulled out just enough to reach the outlet, about 1 foot.

For additional protection, I installed the outlets on the vertical post that makes up one side of the stall door. So, the outlet is facing the side of the bucket and not facing the interior of the stall. Since they're outside outlets, the box cover has the little 'doors' over each outlet. I put the cover on the box so that when the cord is plugged in the little door covers the plug. Makes it kind of difficult to plug it in, but these buckets will only get plugged in once a season. They have a thermostat in them that comes on at 35F and goes off at 60F.