A 3 m² heated bathroom floor costs 63c a day in our worked example. That is $18.90 over 30 days, using 150 W/m² mats at full power for four hours a day and electricity at 35c/kWh including GST.
Below, we show the same calculation for different homes and heated areas. These are planning examples rather than measured household bills. Replace our chosen area, hours and electricity rate with your own to work out a useful starting figure.
The assumptions behind these examples
For someone using the bathroom before work and again in the evening, a timer could allow heating from 6–8 am and 6–8 pm. We use those four hours for these examples. Adjust the times to your routine and the floor’s warm-up response; four hours is a chosen example, not a measured household average.
The 150 W/m² rating is for the S-Mat 150 range in the SmartHeat electric heating mats brochure. Use the actual installed wattage of your selected product when checking your own costs.
Bathroom examples for 60, 120 and 180 m² homes
A 60 m² apartment may only need a small bathroom floor warmed. A larger home may have a main bathroom and an ensuite on separate schedules. In these three examples, we have chosen 3, 6 and 10 m² of heated bathroom floor. The home sizes give context; the confirmed heated area is what enters the calculation.
150 W/m², four full-power hours a day, 35c/kWh
| Home size (example) | Selected heated floor | Installed power | Cost per day | Cost per 30 days |
|---|---|---|---|---|
| 60 m² apartment | Bathroom: 3 m² | 0.45 kW | $0.63 | $18.90 |
| 120 m² home | Bathroom + ensuite: 6 m² total | 0.90 kW | $1.26 | $37.80 |
| 180 m² home | Selected bathroom zones: 10 m² total | 1.50 kW | $2.10 | $63.00 |
The 30-day totals assume the same operation every day. They cover heating electricity at the stated usage rate, excluding installation and the household’s existing daily supply charge. Mark fixed fixtures and required clearances on your plan before confirming the area a mat can cover.
How to calculate your own running cost
Installed power (kW) = heated area (m²) × mat rating (W/m²) ÷ 1,000.
Electricity used (kWh) = power (kW) × hours drawing power. Cost = electricity used (kWh) × your electricity price ($/kWh).
For 5 m² of S-Mat 150: 5 × 150 ÷ 1,000 = 0.75 kW. Four hours at full power uses 3 kWh. At $0.35/kWh, that is $1.05 a day, or $31.50 over 30 identical days.
You can repeat the calculation with the SA Government appliance running-cost calculator. Enter your actual wattage, hours and electricity rate rather than relying on its default price.
Scheduled time and electricity use are different
A timer sets when heating is allowed to run. The thermostat switches the heating off after reaching its set temperature and back on as the floor cools. Four scheduled hours therefore need not mean four hours continuously drawing full power. The SA Government calculator also explains why thermostat-controlled appliances may use less than a full-power calculation.
The amount of cycling depends on insulation, floor construction, weather, temperature settings and the heat needed. A cold floor may need more initial heating than one already warm. We use the full rated power here so the calculation can be checked without guessing a cycling percentage.
Check the thermostat’s energy information, if available, and how it calculates consumption. For a closer measure of this circuit’s electricity use, ask your electrician about suitable metering. A whole-house bill alone cannot separate floor heating from other appliances.
What does research tell us?
A 2017 electric floor heating study (PDF) used monitoring data from five bathroom heaters and modelled ways to shift heating around changing Estonian electricity prices. Its monitoring and simulations are different kinds of evidence. They do not establish a typical Australian bill or a fixed thermostat saving for your home.
What difference does your electricity rate make?
For the same 5 m², 150 W/m² system running at full power for four hours, daily use remains 3 kWh. Only the price changes in this comparison.
Same heating use, three illustrative rates
| Electricity rate | Daily electricity use | Daily cost |
|---|---|---|
| 30c/kWh | 3 kWh | $0.90 |
| 35c/kWh | 3 kWh | $1.05 |
| 40c/kWh | 3 kWh | $1.20 |
Check the usage rate on your bill. The Australian Energy Regulator’s bill guide explains usage charges, daily supply charges and why different rates can apply. With time-of-use pricing, calculate each heating period at its applicable rate. Check any demand charges separately; this simple calculation does not include them.
Does a 200 W/m² mat cost more to run?
At full power, 5 m² of SH-Mat 200 draws 1 kW. Four hours at 35c/kWh costs $1.40, compared with $1.05 for the 150 W/m² example. Both calculations assume continuous full power for the same time.
That is an installed-power comparison, not an energy-efficiency comparison or a prediction at equal comfort. The floor design, required output and thermostat operation matter. Choose a suitable system before estimating its use.
What if you want to heat a larger area?
Using the same assumptions, a selected 20 m² heated area draws 3 kW and costs $4.20 a day; 60 m² draws 9 kW and costs $12.60. These areas are deliberately chosen examples, not heating requirements inferred from house size.
If the goal is heating large living spaces or a whole home, compare running costs and room heating needs across suitable systems. YourHome’s heating and cooling guidance discusses system sizing, zoning and efficient heat-pump options. Floor-warming costs alone do not show the cost of maintaining comfortable room temperatures throughout a home.
Keep running costs and installation costs separate
A running-cost calculation does not price the installation. Ask for a project quote covering the selected heating products, thermostats, floor sensors, electrical work and testing. Check whether floor preparation, insulation, waterproofing, tiling and other trades are included or separate.
For everyday use, heat the zones you need, allow for the floor’s warm-up response and review the schedule when routines change. Suitable floor insulation and reducing draughts can help limit heating demand. Confirm material compatibility and temperature limits before changing the floor design.
Frequently asked questions
Common running-cost questions
Can I use my home’s floor area to calculate bathroom heating costs?
Use the confirmed heated bathroom area. The 60, 120 and 180 m² homes above do not determine their chosen 3, 6 and 10 m² heating zones.
Is 35c/kWh the average electricity rate in NSW?
No. It is an illustrative rate chosen for these calculations. Replace it with the relevant usage rate from your electricity plan.
Does a four-hour timer include warm-up?
Count all time when the heating can draw power. If automatic preheating starts before the displayed comfort period, add that time to your estimate.
Will a thermostat halve my bill?
There is no universal saving. Cycling, settings, insulation and your schedule determine electricity use. The full-power examples do not assume a fixed reduction.
Sources and calculation notes
All dollar examples are SmartHeat calculations using the stated assumptions. The 35c/kWh example includes GST and covers electricity usage only. The sources support the calculation method, product ratings and operating factors; they do not report these example bills. Sources checked 28 October 2026.
SA Government: calculate appliance running costs — the power, time and tariff method, including the effect of thermostat cycling.
Australian Energy Regulator: your energy bill — how usage rates, fixed charges and different tariffs appear on bills.
Australian Government YourHome: heating and cooling — heating demand, system selection, sizing and zoning.
SmartHeat electric heating mats brochure (PDF) — S-Mat 150 and SH-Mat 200 product ratings.
Energy Made Easy: electricity tariffs — single-rate, time-of-use, controlled-load and demand charges.
Uuemaa, Uleksin and Tammoja (2017), WSEAS Transactions on Power Systems, 12, pp. 124–133 (PDF) — bathroom heater monitoring data and cost-optimisation simulations using Estonian electricity prices; overseas evidence, not Australian running-cost averages.