Let's change that so you DO know.
Lets do your pool. An IC60 will produce 2 lbs per day of Chlorine gas. In 26k gallons that equals 9.2 FC per 24 hours (Per pool math which also has all the other models to experiment with) the cell is expected to produce for 10k hours or 416.66 days.
416 days X 9.2 FC = 3827.2 FCs lifetime.
$1500 (shop around deal proce) ÷
3827 FCs is $0.39 per FC
$1800 (higher /gouge-y price) ÷
3827 FCs is $0.47 per FC.
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10% jug from HD at today's price.
8.5 FC in 26k gallons
$4 each. (The cheaper option. The 4pack was $17+)
$.047 per FC.
So today, if you got a fair price on the SWG it would cover the install fee and break even for however long it lasted. Next time (and likely the 3rd cell) would be $500 cheaper without needing the power unit and the math would work more in your favor.
After a few months of rarely being needed at the pool, though, you would give your left arm if needed for another SWG. Not 1 member..... keep in mind these are regular, real world folks.... has ever kicked themselves for waiting to go with hauling LC. I can show you a list that's a mile long the other way.