I was actually shooting for 12 gallons. But after sparging the 5th gallon and testing just that 5th gallon alone, I got an S.G. reading of 1.014. I thought sparging any more would give me a lower S.G. than desired. The original wort drained from the mash gave me an S.G. of 1.060. After transferring all original wort and all sparged wort, mixed together in the 15-gallon pot I got an S.G. of 1.044. Interestingly enough, after the wort cooled down overnight, the S.G. rose to 1.052 with an approximate volume of 9.5 gallons. For what's it worth, the wort in the 15-gallon pot was actually closer to 10.75 gallons prior to the boil. Not sure if that makes any difference or not.
True, a 3500-watt burner would have worked and you are spot-on with the wiring requirements. However, I performed a test on the induction range in my kitchen which has a 3700-watt burner. It took an hour and 15 minutes to get 8 gallons to a rolling boil. Not a huge time savings I'll admit, but I was trying from the get-go of this project to streamline my time as much as possible. That's why I kept coming back to a gas setup. Truth be said, if my only option was a high-pressure burner, I probably would have spent the extra $$$ and gone total electric. This is, of course, a small setup for brewing. I doubt it would be practical for someone wanting to brew, say, 20 gallons or more batches. Just not enough heat to get the job done.
Just so you know, I do have an 1800-watt induction burner that I used to get 3 gallons of water to a strike temp of 175° for sparging. That actually saved quite a bit of time. I filled that 5-gallon pot with 3 gallons of hot water from my faucet and it hit the strike temp in 10 minutes.
At this point, though a small setup, I figure I can brew every 3-4 weeks and have plenty of good ale on hand for myself, friends, and any passerby...