Written by AJ Electrician Near Me | Published on June 2025
When your lights dim the moment you switch on an appliance, it almost always means your circuit is experiencing a voltage drop. This happens because the appliance draws a large surge of current at startup, briefly reducing the voltage available to other devices on the same circuit.
It is common across homes in Sydney and throughout NSW, especially in older properties with outdated wiring. This article covers the main causes, how to tell if the problem is serious, and the fixes that actually work.
Understand Why Voltage Drop Causes Dimming
Every appliance has a startup surge. When a motor-driven appliance like a fridge, air conditioner, or washing machine kicks on, it briefly pulls two to six times its normal running current from the circuit.
That sudden demand drops the voltage across the circuit for a second or two. Lights are sensitive to voltage changes, so they dim visibly during that drop.
A momentary flicker lasting less than a second is usually harmless. If the dimming is prolonged, dramatic, or happens frequently, that points to a deeper electrical issue that needs attention.
The key number to know: your home’s supply voltage in NSW should sit between 216 volts and 253 volts, with 230 volts as the standard. A healthy circuit should not drop noticeably outside that range just because an appliance starts.
Identify the Most Common Causes
Several factors cause lights to dim when appliances start up. Most are fixable, but some require licensed electrical work.
- Overloaded circuits: Too many high-draw appliances sharing one circuit is the most common cause in older Sydney homes.
- Undersized wiring: Homes built before the 1980s often have wiring that cannot handle modern appliance loads without voltage drop.
- Loose connections: A loose wire at a switchboard, outlet, or junction point creates resistance that worsens under load.
- Faulty or aging switchboard: Old fuse-based switchboards common in NSW homes from the 1960s and 1970s struggle to manage today’s electrical demands.
- Long cable runs: The further electricity travels from the switchboard, the more resistance builds up, especially in larger homes or properties with long spans to outbuildings.
- Weak supply from the grid: Occasionally, the dimming comes from voltage fluctuations in the street supply, not your internal wiring.
Pinpointing the exact cause matters. A flicker that looks identical on the surface can have very different underlying reasons, and each one has a different fix.
Know Which Appliances Are the Worst Offenders
Not all appliances cause the same level of dimming. Motor-driven and heating appliances draw the heaviest startup surges.
| Appliance | Typical Startup Surge | Dimming Risk |
|---|---|---|
| Ducted air conditioner | 3x to 6x running current | High |
| Refrigerator compressor | 3x to 5x running current | High |
| Washing machine | 2x to 4x running current | Moderate to High |
| Pool pump | 3x to 5x running current | High |
| Vacuum cleaner | 2x to 3x running current | Moderate |
| Microwave oven | 1.5x to 2x running current | Low to Moderate |
| LED lights | Near zero surge | Very Low |
In Sydney’s warm climate, ducted and split-system air conditioners are the number one culprit behind dimming lights. Most households run their AC heavily from November through March, putting real strain on circuits.
Pool pumps are also a major factor in suburban NSW homes with backyard pools. If your pool pump causes lights to dim every time it cycles on, your dedicated circuit may need upgrading.
Recognise When Dimming Becomes a Safety Warning
A brief, one-second flicker when the fridge compressor kicks in is usually not dangerous. But certain dimming patterns suggest a more serious problem that poses a fire or electrocution risk.
Contact a licensed electrician immediately if you notice any of these warning signs:
- Lights dim for more than two or three seconds at a time.
- Dimming happens across multiple rooms or on different circuits.
- You hear buzzing, crackling, or popping sounds from your switchboard or outlets.
- Lights flicker even when no appliance has been switched on.
- Circuit breakers trip regularly alongside the dimming.
- You notice a burning smell, warm outlet covers, or scorch marks anywhere.
- Your switchboard still uses ceramic fuses or rewirable fuse wire.
These signs can indicate loose connections, failing wiring, or an overloaded main supply cable. In NSW, these are classified as electrical defects that require urgent attention under AS/NZS 3000 wiring standards.
AJ Electrician Near Me responds to urgent electrical faults across Sydney and regional NSW. If any of the above applies to your home, call 1300 617 337 before the issue escalates.
Compare the Most Effective Fixes
The right fix depends entirely on the cause. Here is a breakdown of common solutions, typical costs in NSW, and what each one addresses.
| Fix | What It Solves | Estimated NSW Cost | Licensed Electrician Required? |
|---|---|---|---|
| Dedicated circuit for high-draw appliance | Overloaded shared circuits | $300 to $700 | Yes |
| Switchboard upgrade | Old fuse board, insufficient capacity | $1,200 to $2,500 | Yes |
| Wiring upgrade (partial or full rewire) | Undersized or degraded wiring | $3,000 to $10,000+ | Yes |
| Tighten loose connections | Resistance from poor connections | $150 to $350 call-out | Yes |
| Soft starter installed on appliance motor | Reduces startup surge on large motors | $200 to $600 | Yes (for hard-wired appliances) |
| Contact energy retailer about supply voltage | Grid-side voltage fluctuation | Free | No |
Do not attempt to rewire circuits or work inside your switchboard yourself. In NSW, all electrical work beyond changing a light globe must be carried out by a licensed electrician. Unlicensed electrical work is illegal and can void your home insurance.
The most cost-effective first step is usually an electrical inspection. An electrician can measure actual voltage drop under load, check connection integrity, and tell you exactly what is causing the problem before you spend money on a fix.
Understand NSW Rules and What They Mean for Your Home
New South Wales follows the AS/NZS 3000 Wiring Rules, which set maximum allowable voltage drop limits. For final sub-circuits in a home, the acceptable voltage drop is no more than 5 percent of the supply voltage.
At 230 volts, that means your lights and appliances should not experience more than an 11.5 volt drop under normal operating conditions. If your lights are dimming noticeably, the drop likely exceeds this limit.
Older Sydney homes, particularly those built in the 1950s through to the 1980s, were wired with 1.0mm or 1.5mm cable, which has higher resistance than the 2.5mm cable required today for power circuits. Many of these homes are now running far more appliances than the wiring was ever designed to handle.
Under NSW Fair Trading regulations, any homeowner who upgrades a switchboard or installs new circuits is entitled to a Certificate of Compliance for Electrical Work (CCEW). Always ask for this certificate. It is your proof the work was done safely and legally.
FAQs on Why Lights Dim When Appliances Turn On
Is it normal for lights to flicker when the air conditioner turns on?
A very brief flicker of under one second is common when a large air conditioner compressor starts. However, if the dimming is noticeable or lasts more than a second or two, your circuit is likely overloaded or undersized for the load. An electrician can install a dedicated circuit for the AC unit to solve this.
Can dimming lights cause damage to my appliances or electronics?
Short, infrequent voltage dips are unlikely to damage most appliances. But repeated or prolonged voltage drops can stress motor windings in fridges, washing machines, and air conditioners over time. Sensitive electronics like computers and televisions are also vulnerable to repeated voltage fluctuations.
Why do my lights dim in only one part of the house?
Dimming limited to one area usually means the problem is on a specific circuit or branch wiring, not the main supply. A loose connection, overloaded circuit, or undersized cable on that particular circuit is the likely cause. An electrician can trace the fault and fix it without affecting the rest of your home.
How do I know if my switchboard needs upgrading?
If your switchboard still has ceramic fuses or rewirable fuse wire instead of modern circuit breakers, it almost certainly needs upgrading. Other signs include a full switchboard with no spare circuits, frequent tripping, or visible rust and corrosion on the board. AJ Electrician Near Me can assess your switchboard and advise on the best upgrade path.
Can I fix dimming lights myself?
No. In NSW, all electrical fault-finding and rectification work must be done by a licensed electrician. The only things a homeowner is legally allowed to do are replace light globes, reset a tripped circuit breaker, and replace socket-outlet covers. Anything inside the switchboard or behind the wall requires a licensed electrician.
How much does an electrical inspection cost in Sydney?
A standard electrical inspection in Sydney typically costs between $150 and $350 depending on the size of the property and what is being checked. Many electricians, including AJ Electrician Near Me, will apply the inspection fee toward any repair work that follows. It is the most efficient way to diagnose dimming issues accurately.
Wrap Up and Next Steps
Dimming lights when an appliance starts usually points to voltage drop caused by an overloaded circuit, old wiring, or a loose connection. Brief flickers are often minor, but prolonged or frequent dimming is a warning sign you should not ignore.
Getting a proper inspection is the fastest way to know exactly what you are dealing with and what it will cost to fix. AJ Electrician Near Me provides electrical inspections, switchboard upgrades, and circuit installations across Sydney and all of NSW.
Call us on 1300 617 337 to book an inspection or request a quote. Our licensed electricians will diagnose the problem quickly and give you a clear, honest recommendation.
