The answer to this question will depend on a whole host of variables related to electric floor heating, including, but not limited to, the run time (for supplemental heating, we usually recommend between 4-8 hours per day), the electric radiant floor heating system you're using, the total square footage, and your local electrical cost. Typically, the cost is just a few cents a day.
To figure out how much electric floor heating might cost to run for you, make sure to use our interactive Operating Cost Calculator.