How hot is too hot for a consumer unit?

A consumer unit should be at room temperature or only very slightly warm. If it is noticeably warm to touch, or too hot to hold your hand against, there is a problem that needs urgent investigation.

Can a hot fuse box cause a house fire?

Yes. Overheating connections can reach temperatures high enough to melt plastic and ignite surrounding materials. Consumer unit fires are a real risk and the reason this is treated as an emergency.

Should I turn everything off?

Turn off the main switch in the consumer unit. This stops current flowing through the faulty connection and allows it to cool. Call an emergency electrician and do not turn it back on until they have inspected it.

What causes a consumer unit to overheat?

The most common cause is a loose connection. As the connection degrades, its resistance increases, which generates heat. This gets progressively worse over time if not addressed.

Emergency

Updated 30 August 2026

Consumer Unit Is Hot

Your consumer unit or fuse box is hot to the touch — this is a fire risk that needs immediate attention.

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What's happening?

A consumer unit that is noticeably warm or hot to the touch has an internal fault causing excessive heat generation. This is most commonly caused by a loose connection — electricity flowing through a high-resistance connection generates heat. A hot consumer unit is a fire hazard because the heat can melt plastic components, damage cable insulation, and in the worst case, ignite surrounding materials.

What usually causes it?

Loose terminal connection on the main switch, MCB, or busbar
Overloaded circuit drawing more current than the components are rated for
Corroded or oxidised connections increasing resistance
Faulty MCB or RCD with high internal resistance
Undersized main tails (cables from the meter to the consumer unit)

Is it dangerous?

This is an emergency. A hot consumer unit means there is excessive heat being generated, which is a direct fire risk. If the unit is too hot to comfortably rest your hand on, or if you can smell burning or see discolouration, turn off the main switch immediately and call an emergency electrician. Do not delay — consumer unit fires can develop quickly.

Can I fix it myself?

No. Turn off the main switch to stop current flow and reduce heat. Do not open the consumer unit cover. If you can smell burning or see smoke, also turn off the main switch on the meter (if accessible) and call the fire brigade if you believe there is an active fire. Call an emergency electrician.

When should you call an electrician?

Call an emergency electrician immediately. A hot consumer unit is a fire risk and should never be left until the next day. While you wait, keep the main switch off and monitor the unit for any signs of smoke or further heating.

What will the electrician actually do?

Isolate the supply and allow the unit to cool before inspection
Remove the cover and use thermal imaging to identify the heat source
Check every connection for tightness and signs of overheating (discolouration, melted plastic)
Replace any damaged components — MCBs, RCDs, busbars, or the entire consumer unit if necessary
Re-torque all connections to correct specifications
Test all circuits and monitor temperatures after restoring power