Heating a terrarium without a thermostat: why it's dangerous
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
Heating a terrarium without a thermostat is one of the gravest risks in reptile keeping: a heat mat plugged in directly can exceed 50 °C and burn the animal, and an unregulated lamp can turn the enclosure into an oven during a heat spike. A thermostat costs 30 to 80 € — a fraction of the price of an emergency vet consultation.
Contents · 5 sections
What actually happens without regulation?
A heating element used “bare” knows only one state: on at full power. The temperature reached then depends on the weather, the room's heating and the enclosure's insulation. The result: belly burns on heat mats (reptiles sense heat poorly through their underside), heatstroke in summer and huge swings between January and July. The heat rock, incidentally, stacks up the very same flaws.
Which type of thermostat should you choose?
- On/off (30 to 45 €): cuts and restarts the heater; sufficient for a mat or a ceramic emitter;
- Pulse-proportional (50 to 70 €): smooths the power output; ideal for ceramic;
- Dimming (60 to 80 €): finely modulates intensity with no flicker; the best choice for halogen lamps;
- With alarm and dual probe: extra safety for large installations.
Where should the probe go for a reliable reading?
Place the probe at the level where the animal lives: on the substrate at the basking spot for a ground-dwelling species, at mid-height for an arboreal one. Fix it firmly — a probe knocked loose by the animal throws off the entire regulation — and double-check weekly with an independent thermometer. During a heatwave, the thermostat cuts the heating but cannot cool: plan ahead with our heatwave and terrarium advice.
Does a thermostat save electricity?
Yes: by cutting or modulating the heater once the setpoint is reached, it lowers consumption by 20 to 40 % compared with running flat out. It also extends the life of bulbs run on a dimmer. Find models and matching accessories in the reptile accessories section.
Frequently asked questions
My heat mat is labelled low-temperature — do I still need a thermostat?
Yes: even a 15 W mat can exceed 45 °C in direct contact under a thin layer of substrate. The thermostat remains essential, whatever the heating element.
Can a thermostat fail?
Rarely, and usually in the off position, which is harmless. For expensive installations, a second safety thermostat set 2 to 3 °C higher protects against a failure stuck in heating mode.
Can you run several heaters on one thermostat?
Technically yes, if the total wattage stays under the unit's limit, but a single probe will govern everything: one thermostat per heating zone is the better setup.
See it in the Planète Pets shop: Stick-on digital thermometer for aquarium and terrarium glass (€18.90) · the whole shop
This guide is part of Planète Pets’s Reptiles universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.
