I live in Tennessee with relatively low utility rate of 9.368 cents per Kilowatt hour. Unless I need to replace my single speed super pump motor due to motor failure it really doesn't make financial sense to purchase even a 2 speed motor much less ever purchase a brand new variable speed pump for $700.00 plus. If I want to be green and help the environment that is another story. Then one could factor in the energy and resources required to build a new motor to replace a working motor. Ok enough of that.
My theory is figured on 6 hours of pump run time per day single speed vs dual speed. Your mileage will vary depending on your run time and your residential electricity rate per kilowatt hour.
A standard 1 hp super pump 56J replacement motor at Electric Motor Warehouse motor draws around 7.5 Amps at 220 V. 7.5 x 220 = 1.650 kilowatts per hour x 6 = 9.900 kilowatts per day. My electricity rate is 9.368 cents per kilowatt hour. 9.368 cents per hour x 9.9 = 93 cents per day x 30 = $27.90 per month running the pump 6 hours per day.
Take the Electric Motor Warehouse Century STS1102RV1 two speed Super Pump replacement motor. According to EMW specs on high the current draw 8.5 Amps and is 2.5 Amps at low speed.
Compared running on high 2 hours per day / on low for 4 hours per day.
8.5A on high x 220V = 1.870 kilowatts per hour
2.5A on low x 220V = .550 kilowatts per hour.
Running 2 hours on high 1.870 kilowatts x 2 = 3.74 kilowatts per day on high.
Running 4 hours on low .55 kilowatts x 4 hours = 2.2 kilowatts per day on low.
3.74 + 2.2 = 5.94 kilowatts per day with a 2 speed motor
5.94 kilowatts x 9.368 cents per kilowatt hour = 56 cents per day to run a two speed motor for 2 hours on high and 4 hours on low.
56 cents per day x 30 days = $16.80 per month.
Total savings of the two speed motor = $27.90 - $16.80= $11.10 per month.
If you are replacing the 56J style motor only -
Single Speed non energy efficient motor model 1102 cost is $156.00.
Dual Speed energy efficient motor model STS1102RV1 cost is $274.00
$274 - $156 = $118.00 dollars difference in the price or 10.6 months running at 30 days per month to recoup the investment.
The point is for me when my motor breaks I will look into a dual speed but most likely not before. I also will need to add the cost of a $150.00 Intermatic 2 Speed digital timer to replace the single speed mechanical timer I have today.
Sorry if I bored you with this post but I started typing and couldn't stop!!