What is this?
A humming or buzzing consumer unit is not normal and indicates something is wrong. The sound is typically caused by a loose connection, a faulty MCB or RCD vibrating, or excessive current flow through a component. In some cases, it can indicate arcing — where electricity is jumping across a gap in a loose connection, generating heat and noise.
Common causes
- Loose cable connection on a terminal inside the consumer unit
- Faulty MCB or RCD that is vibrating internally
- Overloaded circuit causing an MCB to run near its trip threshold
- Arcing at a loose busbar connection
- Mains supply voltage fluctuation causing transformer hum in connected equipment
Is it dangerous?
A humming consumer unit should be treated as a serious warning sign. Loose connections and arcing generate heat, which can melt plastic components and start a fire. If the humming is accompanied by a burning smell, warmth from the board, or discolouration, treat it as an emergency. Turn off the main switch and call an electrician immediately.
Can I fix it myself?
No. Do not remove the consumer unit cover — the internal components carry lethal voltages. You should not attempt to tighten connections or investigate the noise yourself. If the humming is loud or you can smell burning, turn off the main switch and call an emergency electrician.
When to call an electrician
Call an electrician promptly if your consumer unit is humming. If there is also warmth, a burning smell, or visible discolouration, call an emergency electrician immediately. Even a faint hum should be investigated within a day or two, as it may indicate a developing fault.
What will an electrician do?
Inspect the consumer unit with the cover removed (with appropriate isolation)
Use a thermal imaging camera or contact thermometer to identify hot spots
Check and re-torque all connections to manufacturer specifications
Replace any faulty MCBs, RCDs, or busbars
Test all circuits after the repair to confirm safe operation
Typical cost
£80 – £300
Tightening connections and replacing a single MCB is at the lower end. If the consumer unit itself is damaged and needs replacing, expect £350–£600.
