Do you guys actually track to that level of detail?? The way I have been attempting to set up my costs is very similar to this http://www.masterplumbers.com/utilities/costcalc/
link. Figure it in billable to nonbillable. Productive vs nonproductive. Productive is any labor and costs directly associated with that labor that can get allocated to billable time (T&M) or costed time (bid and contract work)I.E.:
liabilty if based on wage exposure
Then nonproductive would be all costs not directly associated with actual install whether bid or T&M. I.E.:
vacation & paid holiday
Figure how many billable hours you are likely to work throughout the year. For me I like to figure at least 1-1.5 hours per day per man nonproductive for stocking the truck, drive time etc. Then as the owner I am shooting for 24 hours productive billable time in the field per week and the rest administartive, meeting, selling etc. But all the productive billable hours have to cover all those overhead expenses plus the extra salary I need to live. I can't live off 24 hours a week. Take your total overhead and divide by billable hours. That is how much per hour over what wages cost you, that you need to charge to break even. Then add profit for growth (all healthy things grow)and you have your hourly rate.
I modified that calculator in a spreadsheet and it can be fun to play with the numbers. See how many more hours I have to work per week if an employee misses a day per week just to make for overhead. also to see how profit suffers if I only bill in 8 hours a week.