My breaker box is a 200 amp service. There's 16 openings and only 1 blank space for a new breaker. I have a garage about 100' away from the house that I'd like to run lights and a few plugs for tools from this panel. (The strongest power draw would be a cheap harbor freight air compressor.)
When I add up the amount of amps on the breakers already in the box, its well over 200. I know not everything runs at once, so how do I know exactly how much I can add to the box before I start dimming the lights in the house when I use a drill in the shop, or if the air compressor kicks on, it throws the breaker? Ideally, I'd like to run it off of the house and not install it's own meter and supply since the power company charges commercial rates for the second meter at a single address.
I know they make sub panels but I don't know when those are the only option or how involved a job it is to add one.
I have enough experience to run the wires and do the plugs/switches but this part is new to me.