From this thread
. Kegs are 18 gauge. Use that as a guide. Kegs are plenty thick for direct fire.
You'll be fine with propane burners. If you want to go electric, go for it but time to boil is a weak reason. I'm from tap to mash in 20-30 mins. That's a bigger jump than from mashout to boil. I crank up my boil kettle with my first runnings and I am boiling by the time I finish a beer. If I get set up to fly sparge I bet I can start my boil timer as soon as my last runnings hit the pot. My brewday goes like this:
Step 1: Fill HLT and start heating
Step 2: Get my act together
Step 3: Overshoot temp because I'm still trying to figure out why my wireless printer only prints over usb
Step 4: Stir MLT to get down to mash in temp
Step 4a: Forget about printer until next brew day