Having read here, there, and everywhere how MUCH a SWG was going to save me, I mulled it over, ran some numbers in my head, and decided to pull the trigger on getting one. I went low budget (thankfully), and now I am almost kicking myself for not running ALL of the numbers first, `cause I'm paying $2.55 per equivalent gallon of 6% bleach!!! How did I get here? Well, it certainly wasn't with vague numbers from sales literature; you have to dig for the fine print.
Some background- after swearing off 3 inch stabilized chlorine tabs (CYA~100) in my auto-feeder, I got a test kit(that was actually first!) and started dosing with Wal-Mart Ultra bleach at $1.68/G, then switched to supermarket Alway-Save brand for $0.99/G. I need about 1/2 gallon/day(~64 oz.) for my 24,000 gallon water feature (almost NO bather load, we sit inside and look out at it 8) ) I still wasn't comfortable with popping up to a grand for a SWG, so I dug for the truth on ACTUAL performance of the various SWG's, in units of chlorine generated per hour, looking to get my needed 64 oz bleach/day in my 10 hour daily pump run time. I went with an Intex A/G Krystal Kleer system I got new on Ebay for $157(including S&H! ), because it generates ~12 oz of 6% Bleach/Hr, meaning I would run it 5-6 hours/day, and I could install it with out re-plumbing. I have ran it 6 hours/day, taking a few days off when my FC was too HIgh. I also plugged it into a Kill-A-Watt meter to see how much energy it actually takes to run, and have kept track of it. Here is my cost breakdown-
SWG Capital Cost $157.00
Salt Capital Cost $63.70
Electric Rate $/Kwhr $0.11 (we're surrounded by coal burning power plants, paying with our health)
Electric Consumed, Kw/Hr 0.1658
Eq. 6% Bl Rate/Hour in Oz. 12 (1.24 chlorine pounds/day max. converted, Thank You! JasonLion)
Expct Cell Life 1000
Gallons of 6% over lifetime 93.75
Lifetime Cost / Gallon $2.55
This is a one year cost, based on (a hopefully worst-case)1000 hour cell life. If my electric rates don't go up, and the cell lasts for another year (it has a two year warranty), my Lifetime Cost/G drops to $1.37, a third year will drop it to $0.98, a fourth to $0.78, and (I'm praying for this ) at 5 years to $0.67. Note that if I replace the cell once(@$157) my 5 year cost goes to $1.00. I did not include ANY installation cost, as I have a removable set-up. Am I going to keep it? Yes, I have already spent the money. I could have spent $800 for a lower end NAME brand SWG with a 5 year cell life, and paid $2.04/G, or $1500 for a high-end model with a 10 year warranty and paid $1.86/G, so I'll be happy to get two years. If I were fortunate/unfortunate? enough to live in a nicer climate where electric rates are ~$0.30/KwHr those last two numbers would be $2.37, and $2.20.
As to claims that SWG are cheaper than bleach- NO WAY, unless they last a LONG time! Convenient-YES, if you can figure out how to use them.
My assumptions are that these systems have the same power/chlorine conversion efficiency, no installation cost, no transport cost for getting bleach,no bonus for convenience. For those that want pool chemistry numbers-
FC= 7.0, FAS-DPD 10ml sample
Oh, yeah, I also didn't account for MA addition for Ph control due to SWG. Tabs drove Ph down, bleach was neutral, and it keeps creeping up now.
I hope that my experience helps those on the SWG fence to feel more at ease, waiting for the NAME brand capital cost to drop, or going low budget, is in my opinion, very prudent.