I always did the "per opening" pricing with the service separate. 3-gang switch= 3 openings. My prices were $30.00 per opening with NM boxes and $37.00 per opening with steel boxes. The recessed light fixtures and trims were cost of materials plus the per opening price. 240V circuits were priced individually depending on the length of run but were generally $125.00 for a range and $75.00 for a dryer. The service entrance is always priced as a package that includes meterbase, entrance conductor, loadcenter, grounding and all circuit breakers. I always include a price list with my contract that shows the per opening price if anything is added at rough-in. It also shows the per opening price if anything is added after sheet rock is up. I don't know how you can make money wiring by the sq.ft. unless you price it high or they are code minimum house wiring jobs. I figured the per sq.ft. price on a custom home I did last spring and it came to $5.50 per sq.ft. A small house(1200 sq.ft.) I did this summer came to $2.50. There are just too many variables.
