Economics of my SWG

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Brad_C

Brad_C

Well-known member
Nov 15, 2018
217
Perth, Western Australia
Pool Size
19000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Monarch ESC24 / ESC7000
My pool chlorine use is ~3.5 ppm/day during summer and about 1ppm/day over winter.

For our cheapest available liquid chlorine that works out at about $1 per day in summer and $0.30 in winter. Split that 50/50 and you get about $237/year in liquid chlorine.

My SWG cost me $875. The first cell lasted 8 years, so $108/year. Plus $15/yr in salt for backwash and top ups.
It gets used for 5 hours a day and draws on average about 80W in summer over those 5 hours. Make it easy and use that all year round. So 146KW/h == $36.50. Total $159.5.

The SWG costs me %67 of what it would cost to use chlorine liquid. Less if I properly did the power sums.

I replaced the cell 2 years ago, and if I get 8 years out of that one then the capital comes down to $62.5/yr.

Not that I needed convincing. Not having to worry about frequent testing or dosing is worth infinitely more, but it's interesting to run the numbers and I was prompted by stumbling across the receipt for this SWG bought back in 2009 earlier tonight.
 
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Brad,

Thanks for the nice analysis. I've found the cost of chlorine has a pretty wide range world-wide and even in the US alone. So the calculation ranges from barely breakeven to a solid payout. When you think about it at a high level, liquid chlorine manufactured at a very large industrial plant is much more efficient. But then you add transportation of the chlorine plus a LOT of water compared to less efficient production in your pool that has none of the transport costs. The variability makes sense. But then there's the most important factor in my case which is my wife loves it and she never wants to have a non-salt pool again. This tips the scale permanently at my pool!

Thanks for your post.

Chris
 
The numbers presented, an eight year cell life, seems much longer than typical. Evidently this system is greatly oversized based on the usage numbers and cell life and it's also been reliable, two things not in everyone's favor. It appears break-even would occur at a 4-5 year cell life that is probably more typical. You are also assuming your cell driver will last for 16 years, if it does then perhaps it should be put in a museum!

As Jim R mentioned, it's not about ROI so much as convenience and reducing waste (labor and packaging).
 
My Compupool CPSC36 just died after 8 years, so maybe not so far fetched? I do believe in bigger being better for longer overall use. Now my fingers are crossed that my generic replacement cell will work at least half that time......

Maddie :flower:
 
Many years ago the numbers were run comparing liquid use and a SWCG based onte "average" life expectancy. At that time the cost was basically a wash, but with the SWCG you were paying for all your chlorine up front.

With the recent rise in chlorine cost in may areas it may not be a wash anymore, but it's probably still close.

Almost anyone who has had one will never switch back.....
 
Not to mention the costs of driving to wherever you have to go to pick up the LC. Gas, tires, oil, other car Crud. Plus your time. Plus I dont have to be home to add the chlorine. I dont care what it costs, I will always have a SWG.
 
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CONVENIENCE .... the intangible value that can only be valued by each pool owner :)
It was ultimately a no brainer for me as we like to have long weekends away and usually have 1 to 2 weeks away in the middle of summer ... liquid chlorine was never going to be the solution
With my relatively small 26,000 litre (6.8k gallon) AGP. I massively overiszed but can generate all i need even in summer in a couple of hours :)
Turned it on for the first time yesterday and noticed that turning the % down changes the actual production rate, cross checked that with the power draw of the unit and power draw went down as % went down indicating that the power unit is using some form of PWM.
 
AusPhil said:
CONVENIENCE .... the intangible value that can only be valued by each pool owner
Click to expand...

In my case i would buy a new $1000 unit every year if need be. My last unit made it 6.5 years and my replacement was only $777. I tested weekly, mostly just to not upset the pool gods. I needed some CYA mid season, and I pressed the more/less button 3 times the whole summer. One click each time. Oh yeah, And i ran boost mode once after the blowout 4th of July party. Thats all i had to do for 6 months. It was a wet season, and it was hot at times and humid as heck. None of it mattered.
 
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I'm considering getting a SWG but is it worth the cost, given I pay nothing for chemicals? The cost of chemicals is included in my pool service which is $125 per month for 2X weekly service. If I do get a SWG, should I request a discount?
 
If you do convert you should ask for a reduction in price. It might not happen. A lot of times services like that are ‘up to XXX amount’ of stuff. If you use less there is no discount. It never hurts to try though.
 
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There is one cost nobody mentioned that's very hard to quantify. I'd call it the "Pain in the rear Cost". Before the SWG I was using pucks in a floater and had nonstop issues with low-level algae, buildup of CYA that required draining the pool 80% and so much brushing I wore them out. I was also buying polyquat.
Since the SWG, zero algae issues, dew-drop water, and less work. We can go away for two weeks and except for my neighbor clearing the skimmer, nothing to worry about. I wish I'd done it sooner. All I'm buying now is acid, and DE for the filter.
Pete
 
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Reading through this makes me really think about a salt water pool. We had a fiberglass install this past October. The PB offered a SWG on his install list, but didn’t mention it. I asked about it and he thought it was a bit overkill with a fiberglass pool. Said it only eliminates one step in sanitation of pool water. I told the wife let’s just get what we need and reassess later. Our pool is closed for the winter and now I’m reading as much as I can. With TFP approach of liquid chlorine and not pucks, it certainly makes SWG a convenient approach. I did ask my concrete installer about our stamped concrete collar and he said with a proper seal it will not have any issues with saltwater. He commented that he does a lot of stamped concrete for newly installed salt water pools and has no issues.
 
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Brad_C said:
I replaced the cell 2 years ago, and if I get 8 years out of that one then the capital comes down to $62.5/yr.
Click to expand...
5 Year update. The cell turns 9 in Feb (I think that means it's going into grade 3 at school and should be able to read, write and do basic mathematics). I've been watching the cell voltage progressively increase as it ages. If I'm careful with pH and CYA I reckon I might get nearly another year out of it.
Fuldo said:
You are also assuming your cell driver will last for 16 years, if it does then perhaps it should be put in a museum!
Click to expand...
It has passed 16 years. It's nearly old enough to drive. Another year it'll be old enough to drink. Museum be Darn.

Looking at the circuitry, the real current carrying part is a basic Triac rectified transformer. It's pretty agricultural. The only real likely failure point may be the capacitors for the switch mode converter that supplies the MCU, and as an electronic technician I reckon I can cope with that if it happens. Oh, and the cell.

On the flip side, in my little slice of paradise the price of replacement cells has gone up nearly 100%, salt has gone up 50% and liquid chlorine about 35% in the last 5 years.

The pool shell is now 56 years old, so it's well overdue for a re-coat. Not bad for a fibreglass pool though.
 
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Brad_C said:
5 Year update. The cell turns 9 in Feb (I think that means it's going into grade 3 at school and should be able to read, write and do basic mathematics). I've been watching the cell voltage progressively increase as it ages. If I'm careful with pH and CYA I reckon I might get nearly another year out of it.

It has passed 16 years. It's nearly old enough to drive. Another year it'll be old enough to drink. Museum be Darn.

Looking at the circuitry, the real current carrying part is a basic Triac rectified transformer. It's pretty agricultural. The only real likely failure point may be the capacitors for the switch mode converter that supplies the MCU, and as an electronic technician I reckon I can cope with that if it happens. Oh, and the cell.

On the flip side, in my little slice of paradise the price of replacement cells has gone up nearly 100%, salt has gone up 50% and liquid chlorine about 35% in the last 5 years.

The pool shell is now 56 years old, so it's well overdue for a re-coat. Not bad for a fibreglass pool though.
Click to expand...
LC has gone up more than 100% around here. Home Depot use to be $4.00, now $9!
 

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