How would I calculate the cost per month for the utility bills in a commercial property?

I am in the market for commercial property for my business, however I need to know how to calculate an accurate estimate for the monthly utility expenses, such as gas, electric, water, sewer, etc. The building we are looking at right now is three stories and a basement, approximately 18,000 sq. ft. The current system is a boiler set up as opposed to forced air, if that helps.