Why is my consumer unit making a humming noise?

Why Is My Consumer Unit Making a Humming Noise? Hearing a hum from your consumer unit (fuse box) is more common than you might think, but it always deserves attention. Here is what it usually means and what you can safely do about it. Most Common Causes Loose busbars or internal connections — vibration from mains electricity (50 Hz) can cause components to buzz if they are not tight A failing or overloaded MCB (circuit breaker) — breakers under sustained load can emit a low hum RCD or RCBO humming — residual current devices sometimes buzz slightly, especially older models Smart meter or surge protection device (SPD) — these contain small components that can generate a 50 Hz tone Normal mains hum — a very faint, barely audible hum can be completely normal on modern dual-RCD boards What You Can Safely Check 1. Listen carefully — is the hum constant or does it change when you switch appliances on or off? 2. Feel for heat — carefully place the back of your hand near (not on) the consumer unit casing. Warmth is a warning sign 3. Smell for burning — any burning plastic smell means call an electrician straight away 4. Check the meter tails area — sometimes the hum originates from the smart meter or its isolator switch, not the consumer unit itself When to Call an Electrician Call a qualified electrician if: The hum is loud or getting louder over time You notice any discolouration, scorch marks, or melted plastic There is a burning smell at any time The consumer unit casing feels warm to the touch MCBs or RCDs are tripping alongside the noise The hum appeared suddenly after a power cut or lightning storm A faint, steady 50 Hz hum that has been present since installation and never changes is often harmless, but any doubt means get it checked. Consumer units contain live parts that cannot be safely inspected without isolation, proper PPE, and test equipment. Do not open the consumer unit yourself.