I may be in need of a new pool pump soon, as my current one is very old. To summarize, I've calculated it costs $255.09 / year to operate my current, single-speed 2HP pump. A service guy recommended a Pentair Intelliflo iF2 Variable Speed pump (model 011009 - 2HP Max). After a rebate from my electric company and a rebate from Pentair, the total comes to $1,024 installed. At this rate, it would take roughly 4 years to break even on the cost of installing the variable speed pump IF MY SAVINGS PER YEAR IS 100%!!! Pentair and Hayward savings calculators typically use higher energy costs and running the pump for 8 hours a day as defaults, which inflates their estimated savings.
Furthermore, the running schedules for a 2HP pump vs a VS pump doesn't seem to equate to any real savings (though I don’t have any real numbers to prove it). For example,
2 HP motor: 4 hours (minimum 3 for vacuum to clean the pool and an additional hour for the water to turn over once)
VS motor: 3 hours @ higher RPM (for pool vacuum) + ??? hours to finish turning the pool water over once)
Can anyone tell me what I’m missing or where I’ve messed up the numbers? I like the idea of a more efficient, quieter pool pump to save energy (and money) and like the idea of the pump running longer for circulation, but it doesn’t seem like a “home run” to go with the variable speed pump given the above. Any advice is appreciated.
Pool Size (in gallons): 18,000
Pump HP: 2
Feet of Head: 60-70 ft.
Pump Flow rate @ 60ft of head: 103 GPM
Pump Flow rate @ 70ft of head: 86 GPM
Time it takes to turn over 18,000 gallons 1 time: 3 - 3.5 hours, so conservatively, 4 hours
Pump's observed energy usage: 2.08 kW
Energy usage for 1 day (2.08 kW x 4 hrs): 8.32 kWh
Energy usage per month (8.32 kWh x 30): 249.6 kWh
Energy usage per year (8.32 kWh x 365): 3036.8 kWh
Current energy rate: 8.40 cents/kWh
Daily Energy Cost: 8.32 kWh x 8.40 cents = $0.70
Monthly Energy Cost: 249.6 kWh x 8.40 cents = $20.97
Yearly Energy Cost: 3036.8 kWh x 8.40 cents = $255.09