Understanding your result
The headline is the cost per month, with the daily and seasonal cost and the heater size beneath it. The stats give the cost per day, per season and the kWh per day; the table lists the heater, the energy and the costs, and the energy per season.
Heater is the heated area times the output per square foot. Energy per day is the heater in kilowatts times the hours it is on, times the duty cycle. Cost per day is that energy times your price per kWh; a month is 30.4 days, and the season is the months you use it.
The heated area comes from the radiant floor heating calculator, which subtracts fixtures and wall gaps. To fold the running cost into a comparison of floors, use the lifespan and cost per year calculator; for the tile that usually goes on top, the floor tile calculator.
How we calculate this
The default electricity price is close to the US Energy Information Administration’s 2026 forecast for the residential average, about 18 cents per kWh; the April 2026 monthly figure was 18.83 cents. Heat outputs come from mat and cable makers’ specifications. The guide to planning radiant floor heat covers sizing and thermostats, the shower tiling guide covers heated bathroom floors, and the installer charges guide covers what installation costs.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Output | 12 W per sq ft (130 W/m²) | Typical mats and cables |
| Hours | 4 per day | A bathroom heated morning and evening |
| Price | $0.18 per kWh (0.30 per kWh metric) | EIA Short-Term Energy Outlook, 2026 US residential average; a typical European price for metric |
| Season | 6 months | A cold-climate heating season |
| Month | 30.4 days | 365 ÷ 12 |
Assumptions last reviewed October 8, 2026.
The calculator assumes the heater draws its full rating while on, which electric resistance heaters do. It does not model heat lost into an uninsulated slab, which makes the floor take longer to warm and run longer, or time-of-use tariffs, for which you should enter the price in the hours the floor runs.
Two worked examples
A 30 sq ft bathroom floor
12 W per sq ft, 4 hours a day, 18 cents per kWh, 6 months.
- Heater: 30 × 12 = 360 W
- Energy: 0.36 × 4 = 1.44 kWh a day; $0.26 a day
- $7.88 a month, $47.28 a season
Less than a streaming subscription for warm floors every winter morning. This is why bathrooms are where most floor heating goes.
A 150 sq ft kitchen at a higher tariff
24 cents per kWh, 4 hours a day, 5 months.
- Heater: 150 × 12 = 1,800 W
- Energy: 1.8 × 4 = 7.2 kWh a day; $1.73 a day
- $52.53 a month, $262.66 a season
Five times the bathroom area and a higher tariff make it a real line on the bill. Running it only when the kitchen is used, and insulating under the heater, are the two savings.
Where to find your inputs
Heated area. From the radiant floor heating calculator or the kit’s heated area.
Output. On the mat or cable specification, in watts per square foot or the total watts.
Hours and duty. From the thermostat’s programme; 100% duty if you entered actual heating hours.
Price. The price per kWh on your electricity bill, including delivery charges.
Common mistakes
- Using the supply charge only. Use the full price per kWh including delivery.
- Leaving it on all day. Programme the thermostat for the hours the room is used.
- Ignoring the duty cycle. A thermostat cycles; hours on are not hours heating.
- The whole room as the heated area. Only the open floor is heated.
- No insulation under a slab. Heat goes down and the cost goes up.
- A 12-month season. Most floors are off in summer.
Questions people ask
- How much does it cost to run electric floor heating?
- A 30 sq ft bathroom mat at 12 W per sq ft draws 360 W. Running 4 hours a day at 18 cents per kWh, it uses 1.44 kWh and costs about 26 cents a day, about $8 a month and $47 over a six-month heating season.
- How much does a heated kitchen floor cost to run?
- A 150 sq ft kitchen floor at 12 W per sq ft draws 1,800 W. Four hours a day at 24 cents per kWh is 7.2 kWh, about $1.73 a day and $53 a month.
- Does floor heating use a lot of electricity?
- Less than people expect in a bathroom, because the area is small and it runs a few hours a day. It adds up in large rooms run all day; a programmable thermostat that heats only when the room is used is the main saving.
- What is the duty cycle?
- The share of the time the thermostat actually has the heater on. If you set the floor to be on for 8 hours but it reaches temperature and cycles at half power, the duty cycle is 50%. If you entered the real heating hours, leave it at 100%.
- What is the average electricity price in the US?
- The Energy Information Administration expects residential electricity to average about 18 cents per kWh in 2026, with New England near 30 cents and parts of the South and Northwest near 12. Use the price per kWh on your own bill.
- Is floor heating cheaper than a space heater?
- Per watt, all electric resistance heat costs the same. Floor heat feels warmer at a lower air temperature because it warms your feet and the surfaces you touch, so people often set the room cooler and use less.