DOE regulations from this fact sheet:
https://image.haywardnotifications.com/lib/fe3d15707564067e721772/m/1/HaywardDOEFactSheet.pdf
» July 19, 2021 is the date non-compliant pumps will no longer be manufactured
» After July 19, 2021, dealers can still buy the older pumps and install them, as long as they can find available inventory
» Customers will not have to return product— and they won’t want to, because the non-compliant models will likely be in high demand from dealers who like their performance and relatively low cost
California is a little different. The onus is on the seller too so that is why it is difficult to find someone who will sell you a single speed although I am told it is not impossible. They can only really catch you if it is a permitted job with inspections.
A 1 HP Whisperflo will use about 2200 watts. An Intelliflo at 1000 RPM will use around 125 Watts. If you are like me and pay $0.30-$0.40/kwh, it doesn't take too much time to make up the difference. Probably less than a year.
But, do you really need to run your pump 8 hours per day? If you ran only 2 hours per day, then it would take 4x longer for payback.
It all depends on the assumptions.