I plumbed into my gas lines to put my brewery in the garage myself. That part is easy. Brewed that way for three years. Even with the back and garage doors open to a cross-breeze there was still not enough adequate ventilation. Brewing could be a real headache- literally.
I moved indoors to my kitchen's gas range and powerful hood vent. It's a bit slower than my ring-burners but I have AC and no headaches. My 80qt fits over two burners nicely at full blast.
In my area (San Antonio) the utilities are as follows: electric per kWh is $0.10525 (peak season) and gas per ccf is $0.87377. One has to do the math to actually figure out whether or not electric is cheaper than gas in your area. With a good electric system your energy needs will be less. What I like about electric is that all the energy goes into the wort and not wasted heating up the pot and the surrounding air. I insulated my kettle and could boil 15 gallons fairly easily with three 1500w elements.
And yes there has to be adequate ventilation for the water vapor. I used to make it rain inside a tiny efficiency apartment when I'd brew double batches. The ventilation sucked.