Temperature Controller — original illustration

Original illustration — a generic example of this tool, not a specific product.

Specifications

Category: Fermentation & Temperature
Function: Reads a probe, switches mains power to a heater or cooler
Outlets: Typically one heat, one cool; some single-outlet models
Setpoint range: Commonly 32–210°F (0–99°C), more than enough
Deadband: Configurable, usually 1–3°F (0.5–1.5°C)
Probe: Waterproof, food-safe stainless, placed directly in the brew
Power rating: Check the amps; do not exceed the controller’s rating
Typical batch size: Any size

Temperature Controller

Switches a heater or cooler on and off to hold a set temperature around the clock.

A plug-in temperature controller reads the brew through a probe and switches a heater or a cooling device on and off to hold a target. It is the most effective single upgrade for consistency, because it removes the daily variation that makes one batch taste different from the next. Most controllers have separate heat and cool outlets with a configurable deadband.

temperature automation heating and cooling

Best for: First Fermentation
Batch size: Any size

Applicable brewing stages

First Fermentation
Second Fermentation
Flavoring
Bottling
Cleaning & Testing

A highlighted stage means this tool has a direct role at that point in the process. Ticking several stages is normal — a thermometer, for example, is useful during both the first and second fermentation.

Safety notes

This is the only device on this list that combines mains electricity, water and an acidic liquid in the same place. Use a controller rated for the load you connect, plug it into a socket with a working earth and, ideally, a residual-current device. Route cables so a spill cannot run into the socket, keep the socket above the vessel, and never place a vessel of liquid directly above powered equipment. If anything smells of burning or feels hot to the touch, disconnect it and stop using it.

Practical guidance

Set the deadband to 2°F (1°C) so the heater cycles rather than chatters.
Tape the probe cable to the outside of the jar and lower the probe in from the top; do not let the cable pull on the probe.
Tape over the controller display with masking tape if the brightness bothers you at night.
Use a plug-in timer as a hard backstop if you are worried about a heater failing on.

Please read before you brew

This page is educational reference material, not professional brewing, food-safety or medical advice. Equipment handling, hygiene practice and local rules vary, and nothing here guarantees a particular brewing result.

Home brewing rules differ by country, state, province and municipality, and they change over time. Check your own local requirements — including any permit, licence, volume limit or minimum age — before you brew, bottle or share what you make.
Use food-grade equipment only. Vessels, bottles, tubing and utensils that were not made for food or drink may release unwanted compounds or shelter microbes.
Work in a well-ventilated space, keep hot liquids away from children and pets, and follow the manufacturer's instructions for every appliance you use.
Bottles under pressure can fail. Use bottles designed for carbonated drinks, do not over-prime, and refrigerate once the carbonation is right.
For anything involving gas pressure, electricity, high heat, chemical cleaners or acids, consult a qualified professional.

Finished kombucha contains trace alcohol and caffeine. It is not suitable for children, and anyone who is pregnant, breastfeeding, immunocompromised, diabetic or taking medication should speak to a healthcare professional before drinking it. Kombucha is a food, not a medicine, and it does not treat, cure or prevent any disease.