Half My House Has No Power — What's Causing It?

What Is a Half House No Power Problem?

When half your house loses power but the other half is fine, you almost certainly have a fault on a specific circuit breaker or group of circuits in your DB board. This is different from a full outage — it tells you the problem is internal and isolated to part of your electrical system.

In homes with larger DB boards, circuits are often grouped by area — bedrooms on one breaker, kitchen on another, and so on. A tripped or failed breaker for one group will knock out everything on that group while the rest of the house continues normally.

In older homes or properties with three-phase supply, a lost phase can also cause exactly half (or a third) of the home to go dark. This is a more serious issue requiring urgent attention.

Common Symptoms & Warning Signs

• Specific rooms or areas have no power while others are unaffected
• Some plugs work but others don't, with no clear pattern
• Lights in certain rooms are off but plugs still work, or vice versa
• One or more breakers in the DB board are in the tripped position
• A breaker cannot be reset — it springs back to off immediately
• Outdoor lights or a specific outbuilding has lost power
• Geysers, stove, or air conditioner stopped working while other circuits are fine

What Causes a Half House No Power Issue?

• Tripped circuit breaker: An overload or fault on one circuit has caused that breaker to trip and isolate that part of the home
• Failed circuit breaker: A breaker has failed in the open (off) position and will not reset
• Lost phase (three-phase supply): One phase of a three-phase supply has been lost, cutting power to all circuits on that phase
• Wiring fault on a specific circuit: A short circuit or earth fault on a circuit has caused the protective device to operate
• Dedicated breaker for high-load appliance: The breaker for the stove, geyser, or air conditioner has tripped due to a fault in that appliance

Checking the DB board for tripped breakers is the logical first step, but only a qualified electrician should investigate why a breaker has tripped or replace a failed breaker.

Need a qualified electrician? Fonster connects you with vetted electricians in your area.

How Urgent Is This?

Partial power loss is a high urgency issue. Even though part of your home has power, the underlying fault — whether a failing breaker, a wiring short, or a lost phase — can worsen quickly and may pose a fire or safety risk.

A lost phase on a three-phase supply is particularly urgent as it can damage three-phase appliances (like some geysers and stoves) that continue to run on the remaining phases. Call an electrician the same day.

DIY vs Professional Repair

Homeowners can safely look at the DB board to identify which breakers have tripped and attempt to reset them once. You can also check whether the problem coincides with a specific appliance being switched on.

Replacing a circuit breaker, investigating why a breaker won't reset, or diagnosing a lost phase requires a registered electrician with the correct testing equipment. These are not DIY tasks — working inside a DB board carries a serious risk of electrocution, and incorrect repairs are illegal under South African electrical regulations.

What Professionals Actually Do

The electrician will first test supply voltage at the DB board to determine if a phase has been lost or if the problem is internal. They'll check each breaker's condition using a multimeter and test the affected circuits for continuity and insulation resistance.

If a wiring fault is found, they'll trace it to the source — often a damaged cable in the wall, a faulty fitting, or a failed appliance connection. Faulty breakers will be replaced with correctly rated units, and the board will be checked to ensure all circuits are properly labelled and protected in line with SANS 10142.

Property Damage Risks

A persistent wiring fault on a circuit that isn't properly protected — or a breaker that has failed in the on position — can allow sustained fault current to flow through wiring, generating dangerous heat and potentially causing a fire inside the walls.

A lost phase left unaddressed will cause single-phase appliances connected to the dead phase to stop working, but more critically, three-phase motors and heating elements that attempt to operate on reduced phases will overheat and burn out, resulting in expensive appliance damage.

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