Check out the article in the July Electrical Contractor magazine on figuring cost for tools and equipment into your costs. The article is by Stan Shook, page 24
www.ECmag.com(Click "EC Mag" tab, then "On the Job" section ... article is called "Figuring in tools and equipment."}
(Or try:
http://www.ecmag.com/index.cfm?fa=article&articleID=7776 }