Which smart thermostat works with electric radiant floor heating?

Two answers circulate, and the sensor is what both skip#

The first answer says to use a Nest or an ecobee. Those are built for 24 V furnace and boiler controls. Electric floor heat runs at 120 or 240 V through the thermostat itself, the same reason they fail on baseboards, as smart thermostats for baseboard heaters explains. Mysa draws the line the same way. It sends hot-water (hydronic) floors and any "24 V floor thermostat" to its 24 V model, and keeps its In-Floor model for "electric mats and cables only."

The second answer says any line-voltage floor thermostat will do, so pick by app. On load, that is nearly right. Four of the six models read here are rated 15 A, Mysa is rated 16 A, and Nuheat's manual gives no rating.

What it misses is the wire already buried in the floor. In a SmartThings thread from 2022, an owner of a Schluter DITRA-HEAT floor asked which other thermostat would work. The first reply compared voltage and load. None of the replies asked which sensor was under the tile, and that is the part you cannot change without lifting it. Mysa says it plainly: "Replacing a sensor under flooring is expensive and disruptive."

The terms the answer rests on#

• Floor sensor. A thin wire with a small tip set in the floor between the heating wires, under the tile. The thermostat reads the floor's temperature through it. Most floor thermostats can also run on air temperature alone, but then nothing watches how hot the floor gets.
• Thermistor, and the "10k" rating. The sensor tip is a thermistor: a part whose electrical resistance changes with temperature. WarmlyYours puts it simply: it reads "lower when warm and higher when cold." The rating is its resistance at 25°C (77°F). A "10k" sensor reads 10,000 ohms at that temperature, and a "12k" sensor reads 12,000 ohms. Makers write this as 10K, 10 kΩ or "NTC 10K @ 25°C."
• Sensor type setting. The thermostat turns ohms into degrees using the curve for one sensor type. Set it to the wrong one and every reading is off.
• GFCI. A ground-fault circuit interrupter cuts power when current leaks out of the circuit, for example through a damaged heating wire into wet grout. Warmup and SunTouch both call theirs "Class A" with a 5 mA trip level, and Schluter says its own trips "to prevent any serious injuries."
• Line voltage. The thermostat switches the floor's own 120, 208 or 240 V power. That is why these are wired into the circuit by an electrician, and why a plug-in device is the wrong tool here.
• Power module. A relay box that lets one thermostat run a floor bigger than its own 15 A limit.

Worked through: an old OJ thermostat over a 12k sensor#

Here is one case, walked through the published figures. Take a bathroom heated by an older OJ Electronics Energystat. The owner wants an app and a schedule. The tile stays.

The sensor. WarmlyYours lists the OJ Energystat as using "a 12K sensor (red & green wires)." So suppose the sensor leads at the old thermostat are red and green. This floor has a 12k sensor.

The load. Suppose the mat's label reads 1,200 W at 120 V. That is 10 A. Every rating in the table below is at least 15 A, so the load rules nothing out.

The candidates, by sensor:

• Sinopé TH1300WF: lists "10K Ω / 12K Ω sensors at 25 °C." It fits.
• Schluter DITRA-HEAT-E-RS1: its floor sensor setting offers "10K or 12K (default: 10K)." It fits, once changed from the default.
• Mysa for In-Floor: takes 5k to 40k, with the value chosen under Settings, Thermostat Preferences. It fits.
• Warmup 6iE: its sensor type menu lists "5, 10, 15, 100K." There is no 12K. It does not fit this floor.
• SunTouch ConnectPlus: its manual says "ALWAYS install the floor sensor included with the thermostat," and that sensor is a 10kΩ type. Reusing the 12k sensor goes against its own instructions.
• Nuheat Signature: the manual read gives no sensor resistance, so it cannot be judged here.

The breaker. Suppose it is a plain breaker. Then any of the three that fit can go in. If it were a GFCI breaker, Mysa would need it swapped first, for the reason in the GFCI section below.

That leaves three choices and no work on the floor. If the old sensor were a 15k, the list would change completely, which is why the sensor comes first.

The floor thermostats, side by side#

As each maker publishes them, read in November 2026. "Not stated" means the document read does not say.

Sources: Sinopé's TH1300WF fact sheet, Mysa's specification, sensor and GFCI pages, and the Schluter, Warmup, SunTouch and Nuheat manuals listed below.

What the table settles:

1. The sensor narrows the list more than the load does. A 12k floor rules out Warmup and SunTouch. A 15k floor rules out Sinopé, Schluter and SunTouch.
2. Mysa reads the widest range by far. Its 5k to 40k covers every common rating, including 15k. DEVI's data sheet for the DEVIreg 530 gives its wire sensor as "NTC 15 kOhm at 25 °C."
3. Mysa is the only one with no way past its limit. Its FAQ says "There is no Mysa power module."

Why the sensor setting matters, not just the fit#

A thermostat set for the wrong sensor does not show an error. It shows a wrong temperature. Schluter's troubleshooting lists "Temperature read by the sensor isn't accurate," and the first cause it gives is that "The resistance value selected for the sensor in the thermostat's settings is not the right one."

Which way it goes follows from how a thermistor works. Higher resistance means colder. So a 12k sensor read as a 10k looks colder than the floor really is. The thermostat keeps heating, and the floor runs warmer than you set. A 10k sensor read as a 12k does the opposite: the floor looks warmer and stays cool.

The warm case is the one to avoid. Floor limits exist for wood and vinyl. Mysa caps the floor at 30°C (86°F) by default, and Sinopé lists "Protection for engineered wood flooring." Both of those limits are worked out from the sensor reading. If the reading is low, the limit is too.

How to find out which sensor is in your floor#

Work through these in order, and stop at the first one that answers.

1. Read the old thermostat. Its manual or its settings menu often names the sensor type. If it had a 10K or 12K setting, note what it was set to.
2. Check the brand. WarmlyYours lists sensor types by brand. "All Aube / Honeywell brand thermostats utilize a 10K sensor (black wires)." "The OJ Electronics 'Energystat' uses a 12K sensor (red & green wires)." OJ Microline touch-screen models "can use either a 10K, 12K or allow for custom sensor settings."
3. Check the mat maker. Schluter's manual tells installers to use "the floor temperature sensor supplied with the DITRA-HEAT-E-HK heating cable(s)," so the mat's papers may name it.
4. Then use a meter, for the right job. With the power off, take the sensor leads off the old thermostat. WarmlyYours says to test on the 20k scale, and that a sensor "typically reads about 8kΩ–15kΩ at normal room temperature." A reading of 0 or OL (open line) means the sensor has failed.

The meter tells you the sensor is alive. It cannot reliably tell 10k from 12k. Warmup says its 10k sensor should read "between 8K ohms and 12K ohms" at 68°F to 86°F. A 12k sensor reads 12,000 ohms at 77°F, inside that same band. So a reading near 12k could be either type. Steps 1 to 3 are how you know. If none of them answers, Mysa is the only model read here whose range covers every rating named on this page.

The GFCI: built in, and sometimes one too many#

Every floor thermostat read here carries its own ground-fault protection. Warmup, Schluter, SunTouch, Nuheat and Mysa all give a 5 mA trip level. Sinopé lists a "Built-in ground fault circuit interrupter (Class A GFCI)." Schluter's RS1 also runs an Auto Test on its own, beside the manual test button.

The catch is the breaker. Mysa says its GFCI "is always on and cannot be disabled." It also warns against a second one: "Two GFCI devices on one circuit conflict, causing constant nuisance trips and preventing the floor heater from operating." If the circuit already has a GFCI breaker or outlet, Mysa says "an electrician needs to fit a standard breaker instead."

SunTouch takes the other view. Its manual says a GFCI or AFCI breaker "may be used, but is not necessary." The Sinopé, Schluter, Warmup and Nuheat documents read here do not say either way.

So look at the breaker before you choose. A GFCI breaker has a TEST button on it. If yours has one, either budget for an electrician to change it, or choose a thermostat whose maker allows it.

More than 15 A: the power module question#

A large kitchen or basement floor can go past one thermostat's limit. Most brands answer with a power module. That is a relay box the thermostat drives, which carries the extra load.

• Sinopé: "For any installation exceeding 15 A, use the expansion unit," the TR1310.
• Schluter: the DITRA-HEAT-E-RRS adds 15 A each, with up to 10 per thermostat. Schluter says it is "the only model which can be used with" the RS1, and it has its own Class A GFCI.
• Warmup: the Relay-25 carries up to 25 A. With the 6iE's own 15 A, that is 40 A in total.
• SunTouch: "SunStat R4 Relays are used when more than 15 A must be controlled by one ConnectPlus thermostat."
• Mysa: no module. Each thermostat runs one zone, so a bigger floor means more thermostats and more zones.

SunTouch also gives a breaker rule. It calls for a 20 A breaker for loads up to 15 A, and a 15 A breaker only for loads up to 12 A. Mysa asks for a dedicated circuit and copper wire only. If the house has aluminum branch wiring, read smart switches on aluminum wiring first.

Wiring, box and radio#

These are line-voltage devices, so the box matters. Mysa wants a line cable and a load cable, a ground, and a sensor on its terminals. At 120 V its N terminal goes to a neutral. At 240 V it goes to the second hot leg, since there is no neutral. A white wire in a 240 V box is not proof of a neutral, as the neutral wire guide explains. SunTouch's ConnectPlus is 1.9 in deep, so check room in the box with the method in box depth and fill. Mysa also says "A 240V system requires a licensed electrician."

On the radio side, Sinopé, Schluter, Mysa and Warmup all use Wi-Fi on 2.4 GHz, the band Wi-Fi 2.4 GHz pairing problems cover. Sinopé lists Alexa and Google Assistant. Schluter's manual has setup steps for Google Home, Alexa and Apple Home. Mysa lists Apple HomeKit, Google Home and Alexa. Nuheat's manual, dated 2018, lists Alexa, Google Assistant and IFTTT.

A reply in the SmartThings thread pointed to Sinopé's Zigbee floor model, the TH1300ZB, for SmartThings users. A Zigbee thermostat needs a hub, which Zigbee explained and SmartThings cover. None of the documents read say what each thermostat does when the internet drops. The questions to ask are in what still works in an internet outage and local versus cloud control.

Which thermostat, by situation#

For a hot-water floor, the 24 V rules and the C wire question apply instead, covered in smart thermostats without a C wire and smart thermostats and the C wire.

Where this page stops#

This page covers six thermostats, from the documents listed below, read in November 2026. Several manuals were read from copies hosted by retailers. Nuheat's manual gives no sensor resistance or load rating, so Nuheat is left out of every ruling that needs one. Brands not read include OJ's current models, Honeywell, Aube, Schluter's other thermostats and WarmlyYours' own, so the page makes no claim about them beyond WarmlyYours' sensor list. That list is from 2018. The meter check proves a sensor works, not which type it is. The sensor ranges are each maker's stated range: a sensor inside it can still need an offset, which Schluter offers from -18°F to +18°F. Ground-fault rules for heated floors come from the electrical code where you live. Your electrician or inspector decides how they apply, including whether a breaker can be changed. Most of this work is line voltage in a wet room. Renters should read a smart home for renters before touching it, and anyone buying for several rooms should add the sensor type and breaker to the pre-purchase checklist.