Hi Bob, I got my unit up and running about two weeks ago. I love it! Keeping my temp at 60. I'll have to see what kind of gas bill I get.
Although my pond is covered for the winter it may not be as bad. I'm sure the initial heating from 41 to 60 degrees will be expensive. Since then it only comes on a couple times a day. I have the 220,000 btu unit. I'll give an update later on. I'll post some pics when I get time. I know my Koi are happier!
Daniel