Derek wrote in
:

Well, you can get much more efficient submersibles. I can't remember
the one I used to use (but googling this group would find it and
others) but it used 215W for 5000gph at 3', iirc...

One seasonal advantage of a submerged pump, relative to a pump that sits
outside the pond, is that all the electrical energy that goes into the pump
is dissipated as heat into the water. So in the winter, if your pump is
drawing 100 watts of power, you are adding 100 watts of heat to the pond.

Obviously, depending on your climate and other variables this heat factor
can be a negative in hot weather.

Where I'm located, in central Wisconsin, the pond freezing over in the
winter is a much bigger concern that the water getting too hot in the
summer.

Rich