How much does it cost to run a free estimate call and not get the work? How much does that lost time cost your business? Are the customers getting your free estimate also getting two or three other free estimates? Does this drive the overall profitability of their requests down? Who ends up paying for the lost time? Does the lower closing rate percentage coupled with the usual lower returns on those free estimate calls help or hurt your business? What about our trade in general? Does it really matter what the other ECs in your area do?
The real underlying questions are- where do you want to take your business and how will you get there? Charging for an estimate or not, are simply byproducts of your fundamental planning and vision you hold for your business.