Personally, if one can afford the IntelliFlo VF pump, I'd go for it. I love mine and there is no way that I could have tuned my system as well as I did with a standard 2-speed pump. The savings I get when the solar system is on by running at 48 GPM instead of the 55 GPM with my previous fixed-speed pump is considerable while the savings I get with the solar off running at 26 GPM with the IntelliFlo compared to a 2-speed pump that might have been at around the same speed is also considerable.
If one cannot afford a variable speed/flow pump, then a 2-speed pump is still much better than single speed and will still save a lot in energy costs -- just not as much savings.
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