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120V vs. 240V Floor Heating: Which Voltage Should You Choose?
Choose 120V for heated areas up to 137 square feet (sq ft) and 240V for larger areas. Both voltages produce the same heat, 13.1 watts per sq ft. The difference is how much floor area one 15-amp thermostat can control. Whichever voltage you choose, your thermostat and heater must be wired to the same voltage.
Watch our YouTube video on the differences between 120V and 240V floor heating cables:
Should I use a 120V or 240V electric floor heating system?
The voltage you choose will be determined by the size of the area you plan to heat. Heating cables and mats at both voltages deliver the same amount of power: 13.1W/sq ft. A 120V floor and a 240V floor will feel the same underfoot; what changes is the electrical load each one puts on your thermostat.
A higher voltage means a lower amperage for the same wattage (amps = watts ÷ volts). A 240V system draws half the current of a 120V system with the same output, so one thermostat can control much more heating cable. Each Warmup thermostat is rated for 15 amps, and that limit is what sets the maximum heated area per thermostat.
Which voltage fits my room size?
| Heated area | Recommended voltage | What to know |
| Up to 137 sq ft | 120V | Fits within one 15-amp thermostat. Uses a single-pole breaker. |
| Over 137 sq ft | 240V | Lower amperage lets one thermostat control more area. Requires a double-pole breaker. |
| 274 sq ft and larger | 240V plus additional controls/relays | Extra control equipment is required. Contact Warmup for design assistance. |
Heated area means the floor you will actually cover with heating mat or cable, not the full room. Space under a tub, vanity, toilet, or other permanent fixture is normally left unheated. For more information on heated area, read our Layout Considerations guide.
Worked example: a 150 sq ft heated area
- Output: 150 sq ft × 13.1W/sq ft = about 1,965 watts.
- At 120V: 1,965W ÷ 120V = about 16.4 amps. This is over the thermostat’s 15-amp limit, so 120V does not work for this area on one thermostat.
- At 240V: 1,965W ÷ 240V = about 8.2 amps. This is well within the limit, so 240V is the better choice.
Does the breaker type change between 120V and 240V?
Yes. A 120V system uses a single-pole breaker. A 240V system requires a double-pole breaker, which takes two slots in your electrical panel. If your panel is nearly full, the number of open slots can decide the voltage for you. Ask your electrician to check available breaker space before purchasing a heating system.
Can I wire floor heating for either 120V or 240V?
Yes, floor heating is available in both voltages, but each heater is built for one voltage only and must be wired to match it. Voltage is set when you choose the product, and it cannot be changed afterward.
- A 120V heater connected to 240V power will fail.
- A 240V heater connected to 120V power will not heat as intended.
Warmup thermostats are dual-voltage, which means the same thermostat model works for either supply. This does not mean you can supply any voltage; the voltage you supply must match the heater’s rating.
All thermostat wiring must be done by a licensed electrician. If you are unsure which voltage your thermostat and heating system should use, contact Warmup support before installing. For circuit, wire gauge, and GFCI requirements, see our Electrical Requirements for Warmup Floor Heating guide.
Is 110V the same as 120V?
Yes. 110V, 115V, and 120V all describe the same standard household voltage. Different people and older documents use different numbers for it, but it is one voltage.
There is no separate “110V” floor heating product. If you need 110V, choose Warmup’s 120V products. The same naming variation exists on the higher side: 220V, 230V, and 240V all refer to the same 240V supply.
How do I choose the right voltage?
- Measure the area you will heat. Include only the floor that will be covered by heating mat or cable.
- Compare it to 137 sq ft. For areas at or under 137 sq ft, use 120V. For areas over 137 sq ft, use 240V.
- Check your panel. 120V needs one open single-pole slot. 240V needs two open slots for a double-pole breaker.
- Check whether your area is 274 sq ft or more. Larger installations will require additional controls. Contact Warmup for design assistance.
- Match everything to one voltage. The heater, thermostat wiring, and breaker must all be rated for the same voltage.
- Hire a licensed electrician to do the final wiring.
Voltage quick-reference guide
| 120V | 240V | |
| Also called | 110V, 115V | 220V, 230V |
| Power output | 13.1 W/sq ft | 13.1 W/sq ft |
| Best for | Up to 137 sq ft | Over 137 sq ft |
| Breaker | Single-pole | Double-pole |
| Amperage for the same area | Higher | Half as much |
| 274+ sq ft | Additional controls required | Additional controls required |
Other frequently asked questions
Does 240V floor heating get hotter than 120V?
No. Both voltages deliver 13.1W/sq ft, so the heat output per square foot is the same.
Is 240V more expensive to run than 120V?
No. Both voltages deliver 13.1W/sq ft, and your utility bills you for energy used (kWh), not voltage, so the same heated area costs the same to run at either voltage.
Do I need a dedicated circuit?
Yes. Warmup recommends a dedicated 20-amp circuit for your floor heating system. If your panel has no room, an electrician can check whether an existing circuit can carry the heater’s amperage plus a 20% safety margin.
Who should wire my thermostat?
A licensed electrician should wire your thermostat. Correct system wiring protects both the heater and your home’s electrical system.
Who do I contact with voltage questions?
Contact Warmup customer support at (888) 927-6333 or ussales@warmup.com.
