Thermo Cube TC-3: Set Points, Load Limit and Use With Coop Heaters and Water Heaters
The Thermo Cube from Farm Innovators is a plug-in outlet that switches power on and off by the surrounding air temperature. According to the manufacturer it operates with any 15-amp, 120-volt electric heater or fan. It is sold in several versions: the manufacturer names 35 °F as the set point for home and farm use and 0 °F and 20 °F for engine and battery heaters. In a coop it makes sense for a heater that has no thermostat of its own.
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The short version
A Thermo Cube turns a plain radiant panel into a temperature-switched one. It carries up to 15 amps at 120 volts, far more than any coop device draws. Buy the version with the 35 °F set point, which the manufacturer assigns to home and farm use, and check the listing, because other versions switch at 0 °F or 20 °F. It reads the air at the outlet, not at the roost or in the water. Devices with a built-in thermostat do not need it.
The Thermo Cube is the simplest way to stop a coop heater from running on mild days: a plug-in block with a thermostat inside and no dial. That is its strength and its limit. You choose the switching temperature once, when you choose the version.
Thermostat add-onAd
Farm Innovators
Thermo Cube TC-3
A plug-in outlet that switches a heater or heated base by the surrounding air temperature, so it does not run on mild days.
Why here: A thermostat outlet from a farm-supply manufacturer that operates with any 15 A, 120 V electric heater according to its product page. Check that the listing names the 35 °F version.
Best for: Any panel or heated base that has no thermostat of its own.
What speaks for it
Works with any 15 A, 120 V electric heater (manufacturer)
Plugs directly into a standard outlet
Turns a plain heater into a temperature-switched one
What to know first
Sold in several versions (TC-1, TC-2, TC-3, TC-21): the manufacturer names 35 °F for home and farm use and 0 °F and 20 °F for automotive use – check the version on the listing
The manufacturer's page names no switch-off temperature; “on at 35 °F, off at 45 °F” is a seller statement
Switches by the air temperature where it is plugged in, not by the water or the roost
Needs a fixed, GFCI-protected outlet like every device in the coop
Type
Thermostat outlet
Power
up to 15 A at 120 V
Control
switches by ambient air temperature; 35 °F version for home and farm use (manufacturer); switch-off temperature not stated
What the manufacturer states, and what it leaves open
We read the Farm Innovators product page on October 11, 2026. This is what it says and what it does not say.
Point
Manufacturer's product page
Function
Turns the power on and off automatically according to the outside ambient air temperature
Load
Operates with any 15 amp, 120 volt electric heater or fan
Connection
Plugs directly into a standard outlet
Models
TC-1, TC-2, TC-3 and TC-21
Set points for heaters
0 °F and 20 °F for automotive applications, 35 °F for home and farm applications
TC-21
For fans: window, ceiling, exhaust, attic and roof ventilators
Which model has which set point
Not stated on the page
Switch-off temperature
Not stated on the page
Listing mark, warranty terms, indoor or outdoor rating
Not stated on the page
The gap in the middle matters. The Amazon listings call the TC-3 a “Cold Weather Thermo Cube” and one listing states “On at 35F / Off at 45F”. Those are seller statements. They fit the manufacturer's 35 °F set point for home and farm use, but the manufacturer's own page does not print the pair. Before you order, read the switching temperatures on the listing. When the device arrives, read them again on the package.
A version that switches at 0 °F or 20 °F is made for engine block heaters. On a waterer it would let the water freeze long before it turned the heater on.
Load limit: not the bottleneck in a coop
The rating is 15 amps at 120 volts. Coop devices are small by comparison: a radiant panel is rated at 150 watts, a heated base at 125 watts and the largest de-icer on this site at 500 watts. To compare a device with the rating, divide its watts by 120 volts for the amps. The rating covers everything plugged into the cube at once. The limit you are more likely to meet is the circuit that feeds the coop, which is a question for the electrician and is covered under electricity to the chicken coop.
Which coop devices need a Thermo Cube?
The cube adds a thermostat. A device that already has one gains nothing.
Device
Own thermostat?
Thermo Cube useful?
Cozy Coop panel
Cord switch for half or full power, no thermostat (instruction sheet)
Yes
PetNF panel
Power dial, no thermostat
Yes
Sweeter Heater
Overheat cut-off only
Yes, for switching by weather
Farm Innovators HP-125 heated base
Built in
No
Farm Innovators HPF-100, Premier 1 waterer
Built in
No
Farm Innovators utility de-icers
Built in; switch on at about 35 °F water temperature (manufacturer FAQ)
No
Heater or base without any thermostat
No
Yes
Panel without a thermostatAd
Cozy Products
Cozy Coop 150 W panel
A 150-watt flat radiant panel from an established brand that warms the birds next to it instead of the whole coop.
Why here: The typical partner for a Thermo Cube: 150 W with manufacturer data, and no thermostat of its own, so it heats whenever it has power.
Best for: Keepers who have decided to add gentle heat near the roost and want a panel with a manufacturer-documented listing mark.
What speaks for it
ETL-listed for zero clearance, according to the manufacturer
Mounts on a wall through keyhole slots or stands on the included feet
150 W, against the 250 W of a typical heat lamp bulb
Cord is coil-shielded, per manufacturer
What to know first
No thermostat: a cord switch sets half or full power (instruction sheet), so it runs whenever it is switched on unless you add a thermostat outlet
The instruction sheet says “household use only” and dry areas only, while the NFPA asks for equipment made for agricultural or commercial use
6 ft cord: needs a fixed outlet close by, because extension cords do not belong in a coop (NFPA)
Warms only birds within reach of the panel, not the coop air
Still a heat source next to bedding and dust: lower risk than a lamp, not risk-free
Type
Flat radiant panel
Power
150 W, 120 V
Size
19 × 8 × 1 in (wall mount)
Thermostat
none; cord switch for half or full power, over-temperature regulator (instruction sheet)
For the heated base there is a second reason to leave the cube out. The instructions for the HP-125 say to plug the product directly into a properly grounded 120-volt receptacle. The base regulates itself, so nothing is lost by following that. Which base fits which fount is a separate matter, explained under heated bases for chicken waterers.
The combination of panel and cube, and the alternative of a panel with a built-in sensor, are compared on the parent page about chicken coop heaters with a thermostat.
It measures the air where it is plugged in
The manufacturer's wording is “outside ambient air temperature”: the air around the cube. That is neither the roost nor the water.
Inside the coop it reads coop air, on an outside wall it reads outdoor air, and for a water heater air temperature is only a stand-in for the water. Because the set point is fixed, you cannot correct for this at the device. You can only choose where the outlet is. The one temperature in the extension literature, the University of Minnesota's 35 °F inside the coop, is discussed under what temperature a chicken coop should be in winter.
For whom, and for whom not
Reasons to buy
Operates with any 15 A, 120 V electric heater or fan (manufacturer)
No settings: plug in and it switches by itself
Keeps a panel without a thermostat off in mild weather
From a manufacturer that also builds heated waterers and de-icers
Reasons to skip
Fixed set point: the wrong version cannot be adjusted
The manufacturer's page does not print which model has which set point, or the switch-off temperature
Reads the air at the outlet, not at the roost or in the water
One more plug connection that needs a fixed, protected outlet
No listing mark named on the manufacturer's page
It is useful in front of a plain radiant panel and not needed for anything that already switches itself.
Plugging it in
The NFPA tip sheet “Backyard Chicken Coop Safety” gives the frame: “Do not use extension cords in the coop.” Outlets and switch boxes should be designed to keep out dust and water, and electrical work belongs to a qualified electrician. For the cube that means:
It goes into a fixed outlet, not onto the end of a cord.
The outlet should be covered and out of reach of the birds, with the heater's own cord reaching it.
Brush dust and cobwebs from the outlet and the cube regularly, as the tip sheet asks for fixtures and outlets.
The manufacturer's page does not say whether the cube is rated for wet locations. Treat it as a device for a dry, covered outlet. The full sequence for a panel is in how to install a chicken coop heater.
An alternative with the numbers in the title
This selection covers only products sold on Amazon. It is not a market overview. Products are compared by manufacturer and listing data, not by hands-on testing. How we evaluate
The HEATIT column is labeled “Seller data only”; it is shown for comparison, not as a pick.
The HEATIT ET-21*(paid link) states on at 38 °F and off at 50 °F in its listing. We could not open a manufacturer page for it, so its maximum load and any listing mark are not confirmed. Its advantage is that there is one version only, so the switching temperatures are not a matter of picking the right model.
Bottom line
The Thermo Cube does one thing: it gives a heater without a thermostat a fixed switching temperature. Buy the 35 °F version, plug it into a fixed, covered outlet, and do not put it in front of devices that already regulate themselves. How much it saves depends on your weather, so no percentage can be given; the arithmetic is under what it costs to run a chicken coop heater. Whether your flock needs a heater in the first place is the earlier question, and the extension services answer it differently: see do chickens need heat in the winter. Terms such as thermostat outlet and GFCI are explained in the glossary.
Questions keepers ask
At what temperature does a Thermo Cube turn on?
It depends on the version. Farm Innovators names three set points on its product page: 0 °F and 20 °F for automotive uses such as engine and battery heaters, and 35 °F for home and farm uses such as stock tank de-icers and pump houses. The page does not say which model number has which set point and names no switch-off temperature. One Amazon listing states on at 35 °F and off at 45 °F; that is the seller's wording.
What is the difference between the Thermo Cube TC-1, TC-2 and TC-3?
The set point. The manufacturer lists the models TC-1, TC-2, TC-3 and TC-21 together and names 0 °F, 20 °F and 35 °F as the temperatures for heaters, without assigning them to model numbers on its page. The TC-21 is the version for fans. For a coop heater or a water heater you want the 35 °F version, so read the switching temperatures on the listing or the package before you buy.
How many watts can a Thermo Cube handle?
The manufacturer states that it operates with any 15-amp, 120-volt electric heater or fan. The coop devices on this site are rated at 25 to 500 watts on their nameplates, so a single one is a small load for that rating. The rating applies to everything plugged into the cube together.
Can I use a Thermo Cube with a heated chicken waterer?
You can, but most do not need it. Complete heated waterers and the Farm Innovators HP-125 heated base have a thermostat built in and switch themselves. The instructions for the HP-125 also say to plug it directly into a properly grounded receptacle. A Thermo Cube is useful for a water heater that has no thermostat at all, and it would switch that device by the air temperature, not by the water.
Does a Thermo Cube replace a GFCI outlet?
No. It is a thermostat, not a protective device. The manufacturer's product page names no ground-fault protection. The NFPA tip sheet for backyard coops asks for outlets designed to keep out dust and water and for electrical work by a qualified electrician. The cube plugs into such a fixed, protected outlet; it does not turn an unprotected one into a safe one.
Coop heat, winter water and the sources behind both
We are the editorial team at chickencoopheater.com. We read what university extension services, the NFPA and manufacturers publish about heating a coop and keeping water liquid, and turn it into plain-English buying advice with the sources on every page.