You should get a SWG rated for at least 2 times your pool volume.
Being in AZ, 3 times (or more) the pool volume would be better.
Consider a 40k or larger SWG.
I'm in Chandler and installed a Circupool RJ45+ on my 12,300 gallons pool. SWG only runs 9 hours per day - even in the heat of summer - and has never been set higher than 70%.
In winter, you may have to supplement with liquid chlorine for a couple months as the SWG will stop producing when the pool water temp drops somewhere below 55-60 degrees. But the pool uses way less FC in winter - I only needed 1 gallon of chlorine all winter.
Initially, you may not see a cost savings. With a SWG, youare buying all your chlorine up front. The piece of mind, no more jug lugging, etc. Is an added benefit. After a few years and taking good care of your water chemistry, the cost benefits increase.