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Fridge and freezer temperature monitoring and alerts

Fridge temperature monitoring uses wireless sensors in each unit and a small Home Assistant hub to log readings around the clock. It keeps records for your food safety checks and alerts staff, then the owner, when a unit stays out of its safe range.

An example of how the studio would build it. No live services are connected.

From a sensor in the fridge to an alert before stock is lost.

  1. Step 01

    Reading reported

    Each sensor sends its temperature to Home Assistant every few minutes.

  2. Step 02

    Record kept

    Log readings to Google Sheets at set times, giving a daily record for each unit.

  3. Step 03

    Range checked

    Compare readings with each unit’s safe range, allowing for short rises from door openings and defrost cycles.

  4. Step 04

    Staff alerted

    Send a push alert through the Home Assistant app when a unit stays out of range for longer than allowed.

  5. Step 05

    Owner escalated

    If nobody acknowledges the alert, notify the owner or keyholder, including out of hours.

The result

Problems are caught before stock spoils, with records to show for it.

An alert needs a reading to stay out of range for a set time, so a door left open briefly doesn’t wake anyone. The workflow only reports: a person decides what happens to the stock and records the action taken.

Before we connect it.

Where this is useful

Useful for cafés, restaurants, butchers, florists and clinics with medicine fridges, where a failure overnight can mean throwing stock away. A sensible first version covers the most valuable units with logging and alerts, while staff keep their manual checks until the readings have proved reliable.

What we need to connect

  1. 01Wireless temperature sensors suited to fridges, ideally with a probe on a lead so the radio sits outside the metal cabinet.
  2. 02A Raspberry Pi or similar small computer running Home Assistant on your network, and the Home Assistant app on the phones that receive alerts.
  3. 03The safe range and alert delay for each unit, taken from your food safety plan or the storage instructions for what is inside.

What needs careful handling

Metal cabinets can block wireless signals, so a sensor that stops reporting raises its own alert rather than being treated as fine. Defrost cycles and busy service cause short temperature rises, so alerts depend on how long a reading stays high and the delay is set for each unit. If the building loses power or internet, Home Assistant can’t send alerts, so a battery backup and an outside check that the hub is still online are worth considering.

Questions people ask.

Can this replace our written temperature checks?

It can provide the readings, but your food safety plan and your local authority decide what records you need. Many businesses keep a quick daily sign-off by a person alongside the automatic log, at least at first.

Is it suitable for vaccine fridges?

It can add useful alerts, but vaccine storage has its own requirements, such as calibrated data loggers and set recording routines. We would treat it as an extra layer alongside the equipment your guidance requires, not a replacement.

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