Variable speed pumps can save you up to 90% as compared to single speed pumps according to manufacturers, although most people in a real world setting including the guys at Bath Pool & Spa say you will save 60-70%. But that in itself can save you thousands of dollars per year. But that in itself can save you thousands of dollars per year. No pool should be without a variable speed pump. Single speed pumps were all that were available until recently. Then 2 speed pumps came out. They are nowhere near as effective as vari-speed pumps.
Now you know what the costs are and how much you can save, if you have an older pump switch it to a vari-speed model. It will pay for itself in 6 months.