The Costs. The average reported cost to install bathroom floor heating for 100 square feet is $600. The minimum average cost reported for installing bathroom floor heating for 100 square feet is $475.The maximum reported cost for installing bathroom floor heating for 100 square feet is $725.n addition to paying for materials, the total cost of a bathroom floor heating project can vary depending on whether the installation company includes labor as part of the estimate or not. If not, homeowners should expect to spend between an additional $200 and $400 in these costs alone.