How Much Does Heated Flooring Cost to Run?

About 38 cents per heated square foot per month at 6 hours a day and the US average of 17.3 cents per kWh. A 50 sq ft mat (600 W) is about $19 a month, a 20 sq ft mat about $8.

Standard electric floor heating mats are rated 12 watts per square foot, so a 40 sq ft mat draws 480 W. Some cable systems run 15 W per sq ft.

Running 24 hours instead of 6 roughly quadruples the cost, to about $1.50 per heated sq ft a month at the US average rate. The thermostat cycles once the floor is warm, so the real number is lower, but a schedule is the easiest saving.

Laying the mat is a common DIY job under tile. The thermostat connects to a dedicated circuit, and many codes require an electrician for that part. Check your local rules.

About 30 minutes to go from 60 F to 80 F for a mat over plywood, according to Warmup. Over a concrete slab it takes longer because the slab soaks up heat. A programmable thermostat set to start an hour before you use the room covers it, and adaptive start on the OJ UDG4 learns the lead time for you.

Measure only the open floor you walk on, because mats do not go under the vanity, toilet or tub. A 50 sq ft bathroom often takes a 30 to 40 sq ft mat. Pick the kit size just under the open area, and never cut the heating wire to make a mat fit.

No. Cost depends on watts, not volts, and a standard mat is 12 W per sq ft either way. 240V halves the current, so one thermostat can carry more mat: the OJ UDG4 handles 1,800 W at 120V or 3,600 W at 240V. That is why rooms over about 150 sq ft of heated floor go to 240V.

Per hour, usually. A 50 sq ft mat draws 600 W, about 10 cents an hour at 17.3 cents per kWh, against about 26 cents for a 1,500 W space heater. At 6 hours a day that is about $19 a month for the mat and about $47 for the heater running flat out. The mat warms the floor you stand on and is not sized to heat a whole cold room.

Not always, but the circuit must carry the load. A 40 sq ft mat at 480 W draws 4 A at 120V. The NEC treats fixed electric heat as a continuous load sized at 125 percent, so a 20 A circuit carries up to 16 A, about 1,920 W. Floor heating in bathrooms needs GFCI protection, which is why each thermostat on this page has a built-in Class A GFCI.

The running cost is small: about $8 a month for a 20 sq ft mat and about $19 for a 50 sq ft mat at 6 hours a day and the US average rate. The cheapest time to add one is when you are already retiling, because the mat goes in the thin-set under the tile. A kit with the thermostat included means one box to buy.