VS versus Single-Speed Pump Math

[MarkFK]

Nine (maybe?) year-old Hayward Superpump impeller has seized (I managed to free it last year but no luck this year). Exploring VS (Pentair SuperFlo VS) versus replacement of Hayward 1 HP single-speed pump. Would some kind soul with more expertise than I have please help me to ensure my calculations (below) make sense?

Difference in cost between units with install and tax: $713
No rebate from utility company for VS pump.
Off-peak electricity rate including distribution: $0.103/KWh (off-peak period is 12 hours per day, fixed charges not included)
Pool runs for maximum 150 days per year.
Note: KWh for Pentair taken from calculator from their web site for the duration specified at a flow rate of 36 GPM
Not sure about dynamic head loss for pool.

		Hayward	Pentair
KW		1.54	0.37
Hours per day		10	12
Cost per day		$1.59	$0.46
Difference per day		$1.13
Days to break even		631
Seasons to break even		4.2

Supplier quoted typical life of Pentair as between "3 and 12 years," which is not overly helpful given the variability. I'm hesitant to spend the extra $ without a decent guarantee that the pump would last long enough to recoup the difference.

Thanks in advance for any thoughts.
Mark

 

[Chemnut]

Better filtering on low speeds, lower power bills. That pump will last ten years but bearings and seal might need to be replaced. Power cost are just going to continue to rise.

bTW. I just installed that pump on my pool. Crazy quiet, you can set prime speed to lower than 3450 and three timer settings. Very easy to set up. You will need to use the unions supplied so you will need to cut and glue your old pipe to them.

 

[mas985]

Where did you get the KW rating for the SuperPump? The 1 HP SuperPump should not use more than about 1.3 kw.

Also, your run times are probably much longer than necessary. At half the run time, it takes twice as long to recover the cost. Plus at those electricity rates, you could replace the current motor with a two speed and recover the costs much quicker because of lower up front.

A SuperPump at half speed would have about 32 GPM at 300 watts. Why do you need 36 GPM?