We have more temperature extremes here in the mid-Atlantic. Usually because we are just trying to stretch the seasons out. It's not worth that kind of money though. We usually just dive in, shiver for a minute, then deal with it. Solar covers are pretty much the norm here and they do a good job.
I just can't imagine justifying the equivalent of leaving an SUV idling to heat the water. That's what using these heaters seems to be around here.
