Redsy for a residential job, your variables are not near as pronounced as commercial, unless you are talking very large quantities. What I mean by that is a price screw up on a storage room addition to a residence job is a lot softer than a price screw up on a missed fixture in a 400 unit repeat subdivision. Same goes for commercial in general. Your unit price for example for a receptacle is ok to compute if every job is interior wall partions of light guage steel studs, secured well prior to your start, 10' high t-bar ceiling, good jobsite working conditions, well lit, daytime work, and an inspector who limits himself to enforcing codes not preferences. That is going to happen on one out of every three jobs. The other ones are going to have too many trades piled in at once, dark, loose non secured studs left for when the drywall screws will "secure them in place" , bla bla bla. I opt for nuts and bolts instead of unit price myself when I bid commercial, I make better money at it that way.
