Not sure if it helps with your planning but we have a 1bbl system as our pilot system that runs on 2 5500w elements and it takes about 30 minutes to bring it up to a boil. We tried with a single 5500w element and it took way too long to boil. I'd say about 10kW per bbl is a good rough number to shoot for. Once it's boiling you probably need much less to keep it going.
Our 3bbl kettle is gas fired. The positives are that it's easy to clean compared to pulling the heating elements each time and it provides a large area of heat so not much worry with scorching (ours is a forced air burner). The downside is that you have to get gas lines plumbed in, plus make sure to exhaust the gas and have enough make up air. Personally, I like our gas better because cleaning those elements sucks. The electric is easy to control but requires quite the control panel to keep it going. Also, take extreme caution to ground everything because with that much electric and liquids, you don't want to accidentally cook yourself.
Originally Posted by ColdFusion
Kaskaskia Brewing Company