I installed a 5,000 watt water heater element in my boiling kettle following the instructions on http://theelectricbrewery.com/
I use the BK as the hot water bath for a heat exchanger (my immersion chiller) and pump the wort from the mash tun (a 10-gallon cooler with a bazooka screen) through the chiller/heat exchanger and back to the mash tun.
You don’t have to have the control system shown on Electric Brewery. I use 240 volts to get the bath close to the target temp, then switch to 110 V controlled by a Johnson digital controller.
When the mash is complete, drain the first runnings into a pot, then heat the water bath to use as your sparge water. Drain the second runnings into the BK, pour the first runnings in, plug in the BK and boil.
The advantages are that I can brew inside, don’t have to get propane tanks refilled, and can read or watch football while the Johnson controller holds my temps. There’s also a lot to be said for just using the BK to heat the water for Denny Conn’s quick and easy system.