Lights dim when you turn on an appliance because the appliance draws a large surge of current from the same circuit, temporarily reducing the voltage available to your lights. This is called voltage drop, and it is the most common cause of momentary dimming in homes across Parramatta and western Sydney.
A brief, barely noticeable dip is usually harmless. But if your lights dim noticeably every time you switch on the air conditioner, fridge, or kettle, it points to an undersized circuit, an ageing switchboard, or a wiring issue. Powerhub Electrical services homes across Parramatta, Epping, and surrounding suburbs. This guide explains why your lights dim when appliances kick in, when it’s dangerous, and what fixes are available.
What Causes Lights to Dim When an Appliance Kicks In
Every appliance needs a burst of power to start up. This initial surge, known as inrush current, can be several times higher than the appliance’s normal running load. An air conditioner that runs at 10 amps may draw 40 to 60 amps for the first fraction of a second when the compressor starts. That sudden demand pulls voltage away from everything else on the same circuit, including your lights.
In older homes across Epping and Carlingford, this effect is more pronounced because the original wiring was designed for far fewer appliances. A home built in the 1970s with a 40-amp single-phase supply and limited circuits simply cannot handle the load that modern households place on it. According to the NSW Government, the current edition of AS/NZS 3000:2018 (the Australian and New Zealand Wiring Rules) includes updated requirements for circuit protection, dedicated appliance circuits, and RCD coverage on all final sub-circuits in residential installations.
I regularly see homes in the Parramatta region where the air conditioner, fridge, and kitchen lighting all share a single circuit. When the compressor kicks in, the lights dip. It happens every time, and the homeowner assumes it’s normal. It’s not. It’s a sign the circuit layout needs attention.
Appliances Most Likely to Cause Lights to Dim
Not all appliances cause dimming equally. The ones with motors or compressors draw the heaviest startup current. Here is how common household appliances compare:
| Appliance | Typical Running Load | Approximate Inrush Current | Dimming Risk |
| Air conditioner (split system) | 8 to 15 amps | 40 to 60 amps | High |
| Fridge or freezer | 1 to 2 amps | 8 to 12 amps | Moderate |
| Washing machine | 5 to 10 amps | 15 to 25 amps | Moderate |
| Pool pump | 6 to 10 amps | 20 to 40 amps | High |
| Electric oven or cooktop | 15 to 32 amps (continuous) | Minimal inrush, but sustained high draw | Moderate |
| Kettle or toaster | 8 to 10 amps | Minimal inrush | Low |
| Hair dryer | 8 to 10 amps | Minimal inrush | Low |
Appliances with motors (air conditioners, fridges, pool pumps, washing machines) cause the most dimming because of the high inrush current needed to start the motor. Resistive appliances like kettles and heaters draw steady current without a spike. If your lights dim when the fridge cycles on or the air conditioner starts, the appliance motor’s inrush current is outstripping your circuit’s capacity.
Is It Dangerous When Your Lights Dim?
A brief, barely perceptible flicker when a large appliance starts is common and usually not dangerous. But repeated or severe dimming can indicate a problem that needs attention. Here is how to assess the risk:
Momentary Dip That Recovers Instantly
If the lights dim for a split second when the air conditioner compressor kicks in and immediately return to normal brightness, this is typical inrush current behaviour. The circuit is handling the load, but only just. It is worth monitoring, but not an emergency.
Noticeable Dimming That Lasts Several Seconds
If the lights dim and stay dim for two or three seconds before recovering, the circuit is struggling to supply enough current. This sustained voltage drop can damage sensitive electronics, shorten appliance life, and indicate the circuit is at or near capacity. An electrical fault finding assessment can identify whether the issue is a wiring fault, an undersized circuit, or a supply problem.
Lights Dim Across Multiple Rooms
If turning on one appliance causes lights to dim throughout the house (not just the room the appliance is in), the issue is at the switchboard or the mains supply level. This points to an undersized switchboard, a weak incoming supply, or a loose neutral connection. All three require professional investigation.
Dimming Accompanied by Flickering, Buzzing, or Warm Outlets
When dimming is combined with other symptoms like buzzing from switches, flickering lights, or outlets that feel warm, the cause may be a loose wiring connection or an overloaded circuit. These symptoms together indicate a fault that could create a fire hazard. Stop using the affected circuit and call an electrician.
More: How To Tell If You Have An Electrical Overload At Home?
What You Can Safely Check at Home
Before calling an electrician, there are a few observations that help narrow down the cause:
Identify Which Appliance Triggers the Dimming
Pay attention to exactly when the dimming occurs. Does it happen when the air conditioner starts? When does the fridge cycle on? When does the washing machine fill? Noting the specific appliance helps your electrician diagnose the circuit layout quickly.
Check Whether the Dimming Is Localised or Whole-House
If only the lights in the same room or area dim, the appliance and lights are likely sharing a circuit that is too small for both. If lights dim throughout the entire house, the issue is at the switchboard or mains supply. This distinction changes the diagnosis entirely.
Note the Severity and Duration
A split-second flicker is different from a two-second dim. Keep a mental note of how long the dimming lasts and whether it is getting worse over time. Increasing severity suggests a deteriorating connection or a growing load on the circuit.
Check Your Switchboard Age
If your home still has a switchboard with ceramic fuses, rewirable fuses, or no safety switches, it was not designed for modern electrical loads. Homes in Dundas Valley, West Ryde, and Telopea with original 1970s switchboards are the most common candidates for a switchboard upgrade to resolve dimming.
Why This Problem Is More Common in Older Parramatta Homes
Dimming lights are not random. They follow clear patterns tied to housing age, wiring design, and electrical demand. Homes across the Parramatta region are particularly affected for several reasons:
- Single-phase supply with limited capacity
Most older homes in Epping, Eastwood, and Beecroft were built with a single-phase supply rated for a modest number of circuits. These homes now run air conditioners, electric cooktops, EV chargers, and home offices that the original supply was never sized for. When demand exceeds what the supply can deliver, voltage drops and lights dim.
- Shared circuits for lights and power points
In homes built before the 1990s across Carlingford, Denistone, and Marsfield, it was common to wire lighting and power points onto the same circuit. This means your kitchen lights share a circuit with the fridge and kettle. Every time one of those appliances draws a surge, the lights feel it.
- Undersized cable runs
Older homes often used smaller-gauge cable for lighting circuits. Over longer runs (common in larger homes in Pennant Hills and West Pennant Hills), the cable resistance increases, amplifying voltage drop. The further the light is from the switchboard, the more it dims.
- Corroded or loose connections at the switchboard
Over decades, terminal screws loosen, and contact surfaces corrode. This increases resistance at the connection point, which creates a localised voltage drop. PowerHub Electrical regularly finds that tightening and cleaning switchboard terminals resolves dimming in homes across Macquarie Park and Ryde without any major rewiring. For pensioners in the area, a 15% discount applies to all electrical work.
- Ageing mains supply from the street
The cable between the street and your switchboard (known as the consumer mains) can deteriorate over time, reducing the amount of current your home can draw. If the supply itself is undersized, no amount of internal rewiring will fix the dimming. A Level 2 electrician is required to upgrade the supply cable.
How a Licensed Electrician Fixes Dimming Lights
When basic checks don’t reveal the cause, a qualified electrician traces the fault systematically.
Brian Ho, the lead electrician at PowerHub Electrical, explains: “Nine out of ten times, the dimming stops the moment we separate the air conditioner onto its own circuit. The original wiring was never designed for a 3kW compressor sharing a circuit with six LED downlights. Once each load has its own path back to the switchboard, the voltage holds steady.”
Voltage and Load Testing at the Switchboard
The electrician measures the voltage at the switchboard under load. If the voltage drops below 216V (the lower limit of the acceptable range under AS/NZS 3000:2018) when appliances are running, the supply or switchboard is the issue. This test identifies whether the problem is inside the home or on the network side.
Circuit Mapping
Each circuit is traced to identify which appliances and lights share it. If a high-draw appliance like an air conditioner is on the same circuit as lighting, the electrician can add a dedicated circuit to separate them. According to the NSW Government, the Service and Installation Rules of New South Wales set the requirements for how electrical installations connect to the distribution network, including supply capacity and metering.
Dedicated Circuit Installation
The most common fix for dimming caused by shared circuits is installing a dedicated circuit for the high-draw appliance. Air conditioners, electric ovens, and pool pumps should each have their own circuit running directly from the switchboard. This isolates them from the lighting and eliminates voltage drop. Proper appliance installation includes a dedicated circuit as standard.
Switchboard Upgrade
If the existing switchboard cannot accommodate additional circuits, a full upgrade replaces the old panel with a modern unit that has capacity for today’s loads. This includes new circuit breakers, safety switches on every circuit, and room for future additions like EV chargers or solar.
Three-Phase Power Upgrade
For homes with consistently high demand, upgrading from single-phase to three-phase power distributes the load across three separate supplies. This is the definitive solution for homes running multiple air conditioners, workshops, or EV chargers.
After a recent project across multiple rooms in a Parramatta home, the team received this feedback: “Brian has helped with many projects for my family and me. He is super reliable and great with communication. He has so much experience and great attention to detail. I couldn’t recommend him more!!” Sonia Wei. That ongoing relationship is what good electrical care looks like.
Dimming issues don’t always happen during business hours. 24/7 emergency response is available for urgent faults across Parramatta. For pensioners, a 15% discount applies to all work, and new customers receive $50 off their first service.
How to Prevent Lights From Dimming When Appliances Turn On
Most dimming is preventable with the right circuit design and proactive maintenance:
- Install dedicated circuits for high-draw appliances
Air conditioners, electric ovens, pool pumps, and EV chargers should each run on their own circuit. This prevents their inrush current from affecting other parts of the home.
- Upgrade an undersized switchboard
If your switchboard is full, has no room for additional circuits, or still uses ceramic fuses, it needs upgrading. A modern switchboard handles today’s loads without voltage issues.
- Consider three-phase power for high-demand homes
If you run multiple air conditioners, a workshop, or plan to install an EV charger, single-phase may not be enough. A three-phase upgrade distributes the load evenly and eliminates dimming.
- Have loose connections tightened at the switchboard
Corroded or loose terminal connections cause a localised voltage drop. A routine electrical inspection includes checking and tightening all switchboard connections.
- Replace ageing cables on long lighting runs
Older homes with small-gauge cable on long runs experience more voltage drop. Upgrading the cable gauge on affected circuits reduces resistance and stabilises voltage. New customers receive $50 off their first service.
- Ask about your supply cable condition
If dimming affects the whole house, the supply cable from the street may be undersized or damaged. A Level 2 electrician can assess and upgrade it.
More: Why Your Power Bills Are So High and How an Electrician Can Help
Areas We Service
PowerHub Electrical services homes and businesses across Parramatta and the greater western Sydney region, including Epping, Carlingford, Ryde, Eastwood, Beecroft, Dundas Valley, West Ryde, Marsfield, Macquarie Park, Pennant Hills, Denistone, Telopea, West Pennant Hills, Turramurra, and Melrose Park.
Stop Your Lights From Dimming
If your lights dim every time you turn on an appliance and you can’t find the cause, call PowerHub Electrical on 0400 332 331. Licensed electricians, same-day service, 24/7 emergency response, and a 15% pensioner discount on all work. $50 off your first service.
Frequently Asked Questions
Is it dangerous when my lights dim with appliances?
A brief, split-second dip is usually not dangerous. But repeated or severe dimming that lasts several seconds can indicate an overloaded circuit, undersized wiring, or a loose connection. These conditions increase the risk of overheating and should be inspected by a licensed electrician.
Why do my lights dim when the air conditioner turns on?
Air conditioners draw a large inrush current when the compressor starts, sometimes four to six times the normal running load. If the air conditioner shares a circuit with your lighting, this surge temporarily reduces the voltage available to the lights, causing them to dim.
Do I need a dedicated circuit for my air conditioner?
Yes. Under AS/NZS 3000:2018, high-draw appliances like air conditioners should be on their own dedicated circuit. This prevents their startup surge from affecting lights and other appliances. Homes in Parramatta and Epping built before the 1990s often lack dedicated circuits for air conditioning.
Can an overloaded switchboard cause lights to dim?
Yes. If your switchboard is at capacity, adding more appliances overloads the existing circuits. This creates a voltage drop across the board, causing lights to dim throughout the house. A switchboard upgrade adds capacity for additional circuits and resolves the issue.
Should I upgrade to three-phase power?
If your home runs multiple air conditioners, a workshop, or you’re planning an EV charger, single-phase power may not be enough. Three-phase power distributes the load across three separate supplies and eliminates dimming caused by high demand.
When should I call an electrician for dimming lights?
Call if dimming lasts more than a split second, affects multiple rooms, is getting worse, or is accompanied by buzzing, warm outlets, or a burning smell. In NSW, only a licensed electrician can legally modify circuits, upgrade switchboards, or install dedicated appliance circuits.
Will installing a voltage stabiliser fix dimming lights?
A voltage stabiliser can help if the dimming is caused by fluctuations in the incoming mains supply from the street. But it won’t fix dimming caused by shared circuits, undersized wiring, or loose connections inside your home. An electrician needs to diagnose the root cause first. In most cases, a dedicated circuit or switchboard upgrade is the more effective and lasting solution.
Is dimming something I can ignore or does it need to be fixed?
A brief, barely noticeable flicker when a large appliance starts is common and generally not harmful. But if the dimming is obvious, lasts several seconds, or is getting worse over time, it should be investigated. Sustained voltage drop can damage sensitive electronics, shorten appliance life, and in some cases indicate a loose connection that creates a fire risk.
How much does it cost to fix dimming lights?
The cost depends on the cause. A globe or dimmer swap is a straightforward job. A dedicated circuit installation, switchboard upgrade, or three-phase power upgrade involves more time and materials. Rather than guessing, the best approach is to book a diagnostic visit. We provide upfront, transparent quotes after identifying the fault, so you know the full cost before any work begins. No surprises, no hidden fees.
