I've haven't been that busy to worry about something like that, good for you, hopefully I will have that problem soon I wonder about the differences in rates between locations though. I've purchased some estimating books and even though they have different prices for different areas, they still are way off. Usually they are way too high for my area so I don't use them. I would wonder about their ability to compensate for local markets. Although, if you are that busy you don't have to worry about the bids coming in a little high so in your case it may be a good idea to try them out. Although personally I don't know anyone who uses these services it does sound like it's worth a try for a busy contractor. I'll bet you could tailor these services to work with your current prices and labor hours, I'm sure they would be flexible if they want the business. (I.e. our cost on a 200 a panel isn't $550 dollars like some books say it is) Maybe after a few tweaks here and there it would work out well and would be cheaper the hiring an estimator.