If half your house has no power while other rooms or circuits still work, the problem is usually limited to one circuit or a group of circuits rather than the whole property supply. Common causes include a tripped circuit breaker or RCBO, an RCD operating, a faulty appliance, or a wiring or connection fault. Check only what is safely accessible and do not keep resetting protection that trips again.
Key Takeaways
- Partial power loss can affect one circuit, several circuits or one side of a consumer unit while other parts of the home continue working.
- A breaker, RCBO or RCD that trips again after being reset can indicate a fault that needs investigation.
- Do not remove the consumer-unit cover, open sockets or attempt to bypass a protective device.
- If neighbours are also without electricity, the problem may be on the electricity network rather than inside your home.
Why Can Half a House Lose Power?
A home's electrical installation is divided into circuits. Lighting, socket outlets and fixed equipment may be supplied by different circuits, and the exact arrangement varies between properties. A fault on one circuit can therefore cut power to one area while the rest of the property carries on normally.
The pattern can also be wider than a single circuit. An RCD may protect several circuits, so one protective device operating can leave a noticeable section of the house without electricity. That is why “half the house” does not necessarily mean there is one cable supplying exactly half the property.
The useful first question is not simply which rooms are dark, but what has stopped working together: sockets, lights, appliances, one floor, or several otherwise unrelated areas.
Common Causes of Partial Power Loss
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A tripped breaker or RCBO
A protective device can switch a circuit off when it detects a condition it is designed to respond to. The rest of the consumer unit can remain energised, so sockets or lights elsewhere in the property may still work normally.
An RCD has operated
An RCD can disconnect the circuits it protects when it detects an electrical fault. Electrical Safety First advises that an RCD which keeps tripping is likely to indicate a fault involving an appliance or the wiring and should be investigated by a registered electrician.
A faulty appliance
A portable appliance connected to the affected circuit can sometimes cause the protective device to operate. If the problem began immediately after a particular appliance was switched on, that timing is useful information for the electrician investigating the fault.
A wiring or connection fault
Damaged wiring, a deteriorated connection or another circuit fault can also interrupt the supply to part of a property. These faults may be concealed behind accessories, inside fixed wiring or within distribution equipment, so finding them normally requires electrical testing rather than visual guesswork.
Safe Checks You Can Make Before Calling an Electrician
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Work out exactly what has lost power.
Check whether the problem affects lights, sockets, one floor or several areas. Do not dismantle electrical accessories to do this.
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Look at the consumer unit from the front.
Check whether a circuit breaker, RCBO or RCD appears to be in a different position from the others. Do not remove its cover.
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Disconnect portable appliances only if it is safe.
If the affected circuit supplies ordinary plug-in appliances, unplugging them can remove a possible faulty load. Do not handle a plug, socket or appliance that is hot, damaged, wet, sparking or showing burn marks.
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Attempt no more than one sensible reset.
If there are no signs of heat, damage, burning, water ingress or another obvious hazard, a tripped protective device may be reset once after plug-in loads have been disconnected. If it trips immediately or the problem returns, leave it off.
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Arrange diagnosis if the cause is unclear.
A persistent partial power loss needs proper circuit testing rather than repeated resetting.
If the circuit will not stay on, or there is no obvious reason for the loss of power, the appropriate next step is to
have the electrical fault investigated.
Electrical testing can distinguish between an appliance problem, a circuit fault, a connection issue and a problem elsewhere in the installation.
What If the Consumer Unit Still Looks On?
Partial power loss is not always accompanied by an obvious switch sitting in the off position. A fault may exist downstream of the consumer unit, a device may not be visibly obvious as tripped, or the problem may involve the supply to the affected circuit.
If every device appears to be on but part of the property is still dead, the separate guide to
power loss while the consumer unit still appears to be on
covers that specific situation in more detail.
Avoid repeatedly operating switches simply to see what happens. The absence of an obvious tripped device does not make concealed wiring or connection faults suitable for DIY investigation.
Could the Problem Be Outside the House?
Yes. Not every loss of electricity is caused by the fixed wiring inside the property. The electricity network, metering equipment or another upstream supply issue can also interrupt power.
A useful first check is whether neighbouring properties have also lost electricity. Ofgem advises consumers to report a power cut to their electricity network operator, which is responsible for the network carrying electricity to homes and businesses. In England, Scotland and Wales, calling 105 connects you with the relevant network operator.
If a faulty electricity meter is suspected, Ofgem advises contacting the energy supplier instead. If you are unsure whether the problem is coming from the network or your own installation, the guide explaining
whether a power outage is always an electrical fault
sets out that distinction more fully.
When Partial Power Loss Needs Urgent Attention
Do not keep attempting resets if the power loss is accompanied by signs of electrical damage. Electrical Safety First advises householders not to ignore burn marks, arcing or crackling sounds, excessive heat, repeated circuit-breaker operation or damaged electrical equipment.
Arrange urgent assistance if you notice:
- a burning smell or smoke;
- sparking or repeated crackling sounds;
- a hot or discoloured socket, switch or consumer unit;
- visible electrical damage or exposed conductors;
- water affecting electrical fittings or equipment;
- a protective device that repeatedly trips alongside another warning sign.
In those circumstances, keep away from damaged or overheating equipment and seek
urgent electrical help
rather than continuing to reset the circuit.
How an Electrician Finds the Cause
The aim of professional fault finding is to identify which part of the installation has failed before repair work begins. The electrician can use the pattern of the outage, consumer-unit arrangement and electrical test results to narrow the problem to the affected circuit, connected equipment or supply path.
That avoids replacing parts simply because they are nearby. A tripped RCD, for example, does not automatically mean the RCD itself needs replacing, and losing power to several rooms does not automatically mean the property needs rewiring.
Once the fault is located, the appropriate repair depends on what testing finds. It may involve an appliance, an accessory, a damaged connection, part of a circuit or another component of the electrical installation.
Official Guidance
The safety and power-cut guidance above is supported by current UK consumer information from:
Still Missing Power in Part of Your Home?
If the affected circuit will not stay on, the cause is unclear or the outage keeps returning, electrical testing is the safest way to locate the fault before repair work is carried out.
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