I have a 24,000 gal saltwater pool with an 8-year old 2 HP Pentair Whisper-Flo single speed pump that I run 8 hours per day. I have a spa spill-over to pool waterfall feature, sidewall suction pool cleaner (The Pool Cleaner) and about 500 sq feet of Suntrek solar on my 2-story roof---ALL hooked up to this pump. I have a Jandy Aqualink RS8 controller (installed 2005, don't know the version of the firmware yet). My 2 hp Pentair gobbles up 3 kilowatts per hour, so that's 24 KWH per day, 720 KWH/month, and in the middle of Tier 4 billing (Southern California Edison), my electrical costs are $0.31/KWH, so it's costing me $7.44/day to run my single-speed pump, which is roughly 1/3 of my total electricity bill (ouch) .
My pool guy who seems quite knowledgeable on this topic, says that if I hook up a variable speed pump, and I am running everything full tilt in the summer (1 turnover plus pool cleaner, spillover, and solar all operating), nothing will work correctly because the pump is running at too low of a flow, over a longer period of time. He says that while it might take 12-18 hours to turnover the pool water, my spa spillover waterfall will reduce to a trickle or nothing, my solar will not heat properly, and my pool cleaner will limp across the pool. This initially sounds like sage advice (pool guy trying to talk me out of variable speed), but I still wonder, even if set at a higher flow setting can I realize cost savings? Are there other solutions? Thank you.