When claiming an office in the home, you would generally include utilities such as electric, gas, trash removal, and cleaning services, but not water (unless the type of business could justify higher than normal water use). 

When you are selling your home after claiming a home office, it is like you are selling two properties – the personal part of the home, and the business (home office) part of the home.  When selling the business portion, the depreciation is taken into account so the basis for the sale will be lower for that portion of your home.  This can sometimes result in a capital gain for only the business portion of the home.