All, thanks for the information.
I setup a line tracker on the water heater and after a couple days checked it and it worked at 3.33 cents per hour. I forgot to input the newer rate I had written down which was $0.069 but had done a calculation before estimating 500 watts. .5kWh x 0.069 cents...
One of my neighbors wanted to use my electricity to run a electric fence (300') and power stock water heaters (10-20 horses). Off hand I thought it would probably be about $1 a day. Their fence, not their heater. What would be fair?