Giving a dumb heater the thermostat it never had

The best plug-in outlet thermostats for 2026

An outlet thermostat sits between an appliance and the wall socket and switches power based on its own temperature sensor, which is how a heater or fan with no thermostat of its own gets one — and it is a different and generally more precise device than a smart plug's app-based scheduling. The specification worth comparing beyond the obvious temperature range is hysteresis, the gap between the switch-on and switch-off temperature: a wide hysteresis saves the appliance from rapid cycling but lets room temperature drift further from the target than a narrow one. We compare sensor placement and accuracy as stated, temperature range, hysteresis where published, maximum load rating, and whether the unit supports both heating and cooling modes.

What we recommend

1. 

   ChiliTec ST35

   ChiliTec's ST35 is an analog plug-in thermostat rated 230 V, max. 16 A / 3 500 W, switching a connected heater or fan on and off around a 5–30 °C setpoint in 1 °C steps. A slide switch sets heating or cooling mode, and the sensor is built into the plug itself rather than an external probe.

   Max. load

   230 V, 16 A, max. 3 500 W — stated by ChiliTec

   Temperature range

   +5 °C to +30 °C, adjustable in 1 °C steps

   Switching behaviour

   ±1 °C threshold, 10-second measurement interval, with a delayed reading ChiliTec says is meant to stop the relay tripping on a passing draft

   Mode switch

   Slide switch between heating and cooling; the connected device is driven in whichever mode is selected

   Sensor

   Internal — reads the air at the plug, not a remote probe

   Protection rating

   IP20, indoor use only

   Dimensions / weight

   H 128 × W 68 × D 39 mm as plugged in; 190 g

   Amazon reference

   B01MZFKWS5 (EAN 4250416312457) — live offer confirmed on DE/FR/IT/ES; listed with no live offer on GB, no ASIN found on US, at check time

   • 3 500 W / 16 A rating is published by name, not left to be inferred from the plug
   • A heating/cooling slide switch means the same unit can drive a fan or a cooling device, not only a heater
   • Internal sensor only — it reads the air right at the socket, which runs warmer than the middle of the room once a heater has been on for a while

   Best for: Adding a numeric-ish setpoint to a heater or fan that only has a low/medium/high dial, in a dry room where the socket sits close to where you actually want the temperature held.

   ≈ 22 €

   Check price on Amazon
2. 

   McPower TCU-330

   McPower's TCU-330 is a plug-in thermostat rated 230 V, max. 16 A / 3 500 W, with a built-in temperature sensor, an ON/AUTO mode switch, and a shuttered socket McPower states is for added shock protection. The temperature range is 5–30 °C, set on an analog dial.

   Max. load

   230 V, 16 A, max. 3 500 W — stated by McPower

   Temperature range

   +5 °C to +30 °C

   Mode switch

   ON / AUTO — the thermostat function only engages in AUTO; McPower's listing doesn't spell out a separate heating-vs-cooling selector the way the ChiliTec ST35 in this same hub does

   Sensor

   Built-in — no external probe

   Shock protection

   Shuttered socket ("Einsteckschutz"), stated by McPower as extra protection against electric shock

   Dimensions / weight

   183 × 117 × 92 mm packaged; 160 g

   Amazon reference

   B075XJY1WC (EAN 4250967316782) — live offer confirmed on DE/FR/IT/ES; no ASIN found on GB or US at check time

   • Same 3 500 W / 16 A ceiling as the ChiliTec ST35 in this hub, published directly rather than left to be inferred
   • Shuttered socket is a stated safety feature the ChiliTec listing doesn't mention either way
   • McPower's own description names both heaters and climate units as compatible loads, but doesn't state how the ON/AUTO switch decides switching direction for a cooling appliance the way ChiliTec's explicit heating/cooling slide does — worth confirming directly with McPower if you plan to control a cooling device rather than a heater

   Best for: A heater or fan you want left permanently under thermostat control — a cellar, hallway, or similar space where a numeric setpoint matters more than a mode switch for cooling devices.

   ≈ 22 €

   Check price on Amazon
3. 

   Elektrobock TS05

   Elektrobock's TS05 is a digital plug-in thermostat with a relay output stated as max. 16 A, switching a connected heater between +3 °C and +40 °C in 0.5 °C steps, with a frost-protection floor at 3 °C and settings that Elektrobock states survive a power cut.

   Max. load

   230 V / 50 Hz, relay output stated as max. 16 A — Elektrobock does not publish a watt figure directly; at 230 V that computes to about 3 680 W

   Temperature range

   +3 °C to +40 °C, adjustable in 0.5 °C steps

   Hysteresis

   0.5 °C, with a stated measurement accuracy of ±0.5 °C

   Frost protection

   Built-in, engaging at +3 °C

   Power-cut behaviour

   Retains its settings through a power outage and resumes automatically, per Elektrobock

   Protection rating

   IP20; stated operating range 0 °C to +40 °C ambient

   Display

   Digital, with + / − and ON / OFF buttons

   Amazon reference

   B00YURX7BI (EAN 8594012221703, plus three further regional EANs on the German listing) — sold and shipped by Amazon on DE at the time we checked. A catalog page exists on FR/IT/ES/GB under a different ASIN (B01BVKTFXU) but carried no live offer or price on any of the four at check time; no listing found at all on Amazon US

   • Widest and coldest-reaching range of the three outlet thermostats in this hub: +3 °C to +40 °C, against +5 °C to +30 °C on the ChiliTec ST35 and the McPower TCU-330
   • A stated frost-protection floor at +3 °C, which neither of the analog units in this hub publishes
   • States its output as "max. 16 A" rather than a watt figure — the 3 680 W equivalent is our own arithmetic at 230 V, not a number Elektrobock itself publishes

   Best for: A cold garage, shed, or outbuilding where frost protection and a wide temperature range matter as much as the day-to-day thermostat function, and where settings surviving a power cut is worth having.

   ≈ 26 €

   Check price on Amazon