Written by H. Irwin Electrical | Published on June 2025
When your lights dim the moment you switch on a large appliance, it almost always comes down to a sudden voltage drop on your electrical circuit. This happens because appliances like air conditioners, fridges, and washing machines draw a large surge of current at startup, temporarily pulling voltage away from your lights.
This guide covers the most common causes, how to tell if the problem is minor or serious, and what Adelaide homeowners should do next. H. Irwin Electrical sees this issue regularly across suburbs like Glenelg, Marion, Plympton, Unley, and North Adelaide, often in homes with ageing wiring or undersized circuits.
Understand Why Voltage Drops Cause Lights to Dim
Your home electrical system delivers power at a fairly consistent voltage, typically around 230 volts in Australia. When an appliance starts up, its motor or compressor briefly demands a much higher current than it needs during normal operation.
That spike in current causes a temporary dip in voltage across the circuit. Your lights, which are sensitive to voltage changes, respond immediately by dimming. Once the appliance reaches its running speed, current draw drops and the lights return to normal brightness.
A brief, barely noticeable flicker lasting less than a second is usually not a cause for alarm. However, if your lights dim noticeably or stay dim for several seconds, that points to an underlying electrical issue worth investigating.
Identify the Most Common Appliances That Cause Dimming
Not all appliances are equal when it comes to startup current. Motor-driven appliances are the biggest culprits because their motors need a large current surge to overcome inertia and get spinning.
| Appliance | Startup Current Draw | Likely to Cause Dimming? |
|---|---|---|
| Reverse cycle air conditioner | Very high (3-7x running current) | Yes, very common |
| Refrigerator / freezer | High (2-5x running current) | Yes, common |
| Washing machine | Moderate to high | Sometimes |
| Pool pump | High (3-6x running current) | Yes, common |
| Power tools (drills, saws) | Moderate | Sometimes |
| Kettle or toaster | Low startup surge | Rarely |
| LED lighting | Very low | No |
In Adelaide, reverse cycle air conditioners are one of the top causes of this complaint. With hot summers pushing air conditioning use hard across suburbs like West Beach, Henley Beach, and Fulham, the electrical load on residential circuits can be significant.
Recognise When Dimming Is Harmless Versus a Warning Sign
A small amount of dimming is normal and happens in virtually every home. Knowing the difference between harmless and concerning behaviour can help you decide whether to call an electrician.
Signs that dimming is probably harmless:
- The dimming lasts less than one second and happens only on startup
- It only occurs with one specific large appliance
- The lights return fully to normal brightness immediately after
- Your home has been wired or rewired within the last 20 years
Signs that you should call a licensed electrician:
- Lights dim noticeably and stay dim for several seconds or more
- Multiple lights throughout the house dim at once
- Dimming is getting worse over time
- You notice flickering even when no appliance has just switched on
- Circuit breakers are tripping at the same time as the dimming
- You can hear buzzing, crackling, or smell anything unusual near the switchboard
If any of those warning signs apply to your home, do not delay. These can indicate loose connections, overloaded circuits, or deteriorating wiring that poses a real safety risk.
Explore the Electrical Problems That Make Dimming Worse
While some dimming is normal, several electrical faults can make the problem far more pronounced. These are the issues that H. Irwin Electrical most commonly diagnoses when Adelaide homeowners call about persistent light dimming.
Undersized or Overloaded Circuits
If your air conditioner or fridge shares a circuit with your lighting, the voltage drop during startup will be felt immediately by the lights. Dedicated circuits for large appliances solve this problem and are now required by Australian wiring standards for certain appliances.
Ageing or Deteriorating Wiring
Many homes in suburbs like Glandore, Kurralta Park, Hyde Park, and Prospect were built in the 1960s and 1970s with wiring that is now decades old. Older wiring has higher resistance, which makes voltage drops during high current events much more severe.
Loose Connections at the Switchboard or Outlets
A loose connection adds resistance to the circuit. Under normal loads it may not be obvious, but the moment a large appliance starts and current spikes, the loose connection causes a significant voltage drop. This is also a fire hazard and should be repaired immediately.
Undersized Main Cable or Service Fuse
In some older properties, the main incoming cable from the street may be undersized for modern electrical demands. This is less common but does occur, particularly in homes that have had multiple large appliances added over the years without an electrical review.
Neutral Faults
A loose or corroded neutral connection at the switchboard or meter box is a serious fault. It can cause unpredictable voltage behaviour throughout the home and should be treated as an emergency.
Compare DIY Checks Versus What Needs a Licensed Electrician
There are a few safe checks you can do yourself before calling an electrician. However, any work inside your switchboard, on your wiring, or at your power points must be done by a licensed electrician under South Australian law.
| Check or Fix | Safe for Homeowner? | Requires Licensed Electrician? |
|---|---|---|
| Note which appliance causes dimming | Yes | No |
| Check if the appliance is plugged into an overloaded powerboard | Yes | No |
| Reduce the number of devices on one circuit by unplugging others | Yes | No |
| Inspect the switchboard for visible damage or scorch marks | Look only, do not touch | Yes, for any repairs |
| Install a dedicated circuit for a large appliance | No | Yes |
| Upgrade wiring or switchboard | No | Yes |
| Test and tighten connections in the switchboard | No | Yes |
If you spot scorch marks, melted plastic, or smell burning near your switchboard, switch off the main power at the meter box if it is safe to do so and call an electrician immediately. Do not attempt to investigate further yourself.
Understand Common Fixes and What They Involve
The right fix depends entirely on what is causing your dimming. A licensed electrician will inspect your switchboard, circuits, and wiring to pinpoint the cause before recommending a solution.
Common solutions include:
- Installing a dedicated circuit: Running a new circuit specifically for your air conditioner, pool pump, or fridge so it does not compete with your lights. This is one of the most effective and cost-efficient fixes.
- Upgrading the switchboard: Older switchboards with ceramic fuses or limited capacity may need replacing to safely handle modern electrical loads. H. Irwin Electrical regularly upgrades switchboards across Adelaide suburbs including Beverley, Richmond, and Somerton Park.
- Rewiring sections of the home: If old or deteriorated wiring is contributing to the problem, targeted rewiring can reduce resistance and improve overall electrical performance.
- Tightening or replacing loose connections: A straightforward repair that can make a significant difference and eliminate a potential fire risk.
- Installing a soft starter on the appliance: A soft starter reduces the initial current spike from motors, which can reduce or eliminate dimming without any changes to the home wiring.
Costs vary depending on the scope of work. Installing a dedicated circuit typically costs between $300 and $700 in Adelaide. A full switchboard upgrade can range from $1,200 to $3,000 or more depending on the size and complexity of your home.
FAQs on Lights Dimming When Appliances Turn On
Is it normal for lights to flicker briefly when the fridge turns on?
Yes, a very brief flicker lasting under a second when a fridge or freezer starts its compressor is common and generally not a concern. If the dimming is noticeable or lasts longer than a second, it is worth having an electrician check your wiring and circuits.
Can this problem damage my appliances or lights?
Frequent or severe voltage drops can shorten the lifespan of sensitive electronics and lighting. LED lights are particularly sensitive to voltage fluctuations. Persistent dimming is a sign your electrical system is under stress and should be investigated before it causes damage or becomes a safety issue.
Why do lights dim in one room but not others?
If only certain rooms are affected, the dimming is likely isolated to a specific circuit that is either overloaded or has a connection issue. An electrician can trace which circuits are involved and identify whether a dedicated circuit or connection repair is needed.
Could my switchboard be the cause?
Yes. An old switchboard with ceramic fuses, corroded connections, or insufficient capacity can struggle to deliver stable voltage when demand spikes. Switchboard upgrades are a common and effective solution, particularly in older Adelaide homes built before the 1990s.
Is dimming lights a fire risk?
On its own, a brief dimming is not a direct fire risk. However, the underlying causes, such as loose connections or overloaded wiring, can be. If you notice dimming alongside buzzing sounds, warm switch plates, or tripped breakers, treat it as a potential hazard and call a licensed electrician promptly.
How do I know if my home wiring is old enough to be a problem?
If your home was built before 1990 and has not had a wiring inspection, it is worth scheduling one. Homes in older Adelaide suburbs like Hyde Park, Unley, Glandore, and Prospect often still have original wiring that may not be adequate for today’s electrical loads.
Wrap Up and Next Steps
Lights dimming when an appliance turns on is usually caused by startup current draw creating a temporary voltage drop. While a brief flicker is normal, persistent or severe dimming points to electrical issues like overloaded circuits, ageing wiring, or loose connections that need professional attention.
H. Irwin Electrical works with homeowners across Adelaide, including Glenelg, Novar Gardens, Marion, North Adelaide, Henley Beach, and surrounding suburbs, to diagnose and fix exactly these kinds of electrical issues safely and correctly.
Call H. Irwin Electrical today on 0432 270 757 to book an inspection or get a quote. Do not wait for a flicker to become a fault.
