There is a common misconception that solar pool heating increases the energy needed to operate a pump. That is NOT true!
It’s true that solar pool heating systems will increase the back pressure on your pump. On a single speed pump, that means your flow rate will be reduced. However, it also means that your energy consumption will be reduced. Without having a degree in fluid dynamics, you make be wondering how a pump can use less energy if the pressure is increased! The short answer is that the pump is doing LESS work – it’s moving less water.
This is a simplistic explanation of how a pumps energy requirements relate to the flow rate and system pressure, but suffice it to say that at a constant pump speed, less flow means less energy consumed.
Here is a little video I put together to show a real system in action.
Now, since you are reducing the flow rate with solar pool heating on, you would need to run your pump for a longer period of time to achieve the same turnover/filtration of your pool water. The net result would be no energy savings or loss for the same turnover each day.