How much does it cost to fix Baxi error code E20?

Typical repair cost for the Baxi E20 fault is £90-160 including labour.

E20 High

Baxi E20 Fault Code

Q: What does the Baxi E20 fault code mean?

Your boiler is struggling to monitor the temperature of the water circulating through your radiators, causing the system to stop heating your home.

The Baxi E20 fault code means: your boiler is struggling to monitor the temperature of the water circulating through your radiators, causing the system to stop heating your home.. It appears on 37 Baxi models in our database.

Technical description: Central heating thermistor sensor fault

What causes the Baxi E20 fault?

This fault occurs when the sensor responsible for measuring the temperature of the water in your heating system becomes faulty or loses its connection to the main control board. If the boiler cannot accurately track how hot the water is, it will shut down as a safety precaution to prevents the system from overheating. The most common reason is that the internal component has simply worn out over time or the wiring connecting it has become loose or damaged.

This fault is more common in autumn when the heating is turned on for the first time after summer, as the sudden change in temperature and system pressure can cause an aging sensor to fail.

Typical repair cost £90-160 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Baxi models that show the E20 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Baxi E20 fault code information on this page is sourced and cross-checked against the official Baxi service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026