How much does it cost to fix boiler error code E773?

Typical repair cost for the boiler E773 fault is £150-300 including labour.

E773 Emergency

Boiler Fault Code E773

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code E773 appears across 1 boiler brand and 4 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected that the type of gas being supplied does not match what the boiler is set up to use, meaning it cannot operate safely. (As reported on Navien NCB 28 HE)

Pick your boiler brand for the E773 fix

Navien E773 4 models

Source

Information for the E773 fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

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