A power surge is a brief jump in voltage above what your appliances are built to handle, and it has two sources: the network outside your property and the wiring and equipment inside it. Lightning, damage to powerlines and transformers, grid switching and power restoration after an outage come from outside. Large motors cycling on and off, overloaded circuits, loose connections and poor earthing come from inside. Knowing which one you are dealing with decides what you fix.
This guide explains each cause in plain terms, what is different for businesses and care facilities, which warning signs matter, and when to call a licensed electrician on the Mornington Peninsula.
TL;DR
- A surge is a short spike in voltage. It comes from outside (lightning, powerline or transformer damage, network switching, power restoration) or inside (big motors, overloaded circuits, faulty wiring, poor earthing).
- "Surge" and "spike" are used for the same thing in everyday talk. Engineers separate them by waveform, not by size.
- Chronic over-voltage is a different problem from a one-off surge. It can come from how the local network is set up, and it needs a measurement, not a guess.
- Unplug sensitive equipment during storms and outages. Surge protectors help, but they are not safety switches and they do not replace sound wiring.
- Repeated blown power supplies, buzzing outlets or flickering lights point to a fault you should have a licensed electrician check.
Table of Contents
- What a power surge actually is
- Causes from outside your property
- Causes from inside your property
- Constant high voltage is not the same as a surge
- Signs your property has had a surge
- Homes, businesses and care facilities face different risks
- Reducing the risk
- Our perspective
- Get a surge and earthing check on the Peninsula
- FAQ
- Sources
What a power surge actually is
Ausgrid describes a power surge as a sudden increase in voltage to an appliance, and says it can damage appliances connected to aerial, electrical or telecommunication wires. That last part matters: the surge does not have to arrive through your power cable. Phone lines, NBN equipment with external connections, and antenna cabling can carry it too.
The Queensland Electrical Safety Office says surges are fluctuations caused by changing electricity consumption, lightning, or damage to power poles, powerlines or grid transformers, and that they can damage sensitive equipment such as computers, televisions and sound systems. Modern appliances with circuit boards are the usual victims. A kettle shrugs most of it off. A smart TV, a router or an inverter air conditioner does not.
Surge or spike: is there a difference?
In ordinary use, no. Power Quality Australia's technical note says transient overvoltages are also known as surges or spikes. Engineers do split them by shape:
- Impulsive transients are very fast, one-directional peaks, the sort lightning or static discharge produces.
- Oscillatory transients ring up and down and fade away, typically after switching a motor, capacitor bank or breaker.
So if an electrician says "transient" or "impulse", they mean what you would call a spike. The practical question is not the label. It is where the energy came from and what is exposed to it.
Causes from outside your property
These are the events you cannot prevent, only prepare for.
Lightning
Lightning is the best-known cause, and it does not need to hit your house. The Australian technical note lists three routes: direct strikes to phase conductors, strikes to poles or shield wires, and indirect induction into nearby power networks. A strike a few streets away can still push a spike down the street's lines and into your switchboard.
On the Peninsula, summer storm cells roll in across Port Phillip and Western Port with little warning, and long overhead rural lines at places like Red Hill, Merricks and Flinders give a storm a lot of conductor to induce current into. That is local reasoning, not a measured statistic, but it is why we see storm-related electronics failures after a thunderstorm and not only after direct hits.
Damage to powerlines, poles and transformers
A tree across a line, a car into a pole or a failing pole-top transformer can all create abrupt changes in supply. The Queensland Electrical Safety Office names damage to power poles, powerlines or grid transformers as a surge source. After a windy night, a flicker followed by a dead fridge is the classic pattern.
Network switching and faults
Distributors constantly reconfigure the network. Power Quality Australia explains that switching utility capacitor banks, circuit breakers and distribution feeders can create oscillatory transient overvoltages, and it identifies network faults and switching operations alongside lightning as causes. You will not see this happening. You will only see the result: a quick flicker, a beep from a clock, a router rebooting.
Power coming back after an outage
This one catches people out. Outages themselves do not make surges, but restoration can. Emergency Victoria advises turning off appliances during an outage to protect them from a possible surge when supply conditions change, and Energy Safe Victoria gives the same advice to switch off and unplug appliances during a power failure. Leave one light on so you know when supply returns, then plug things back in after a few minutes of steady power. Our guide to what to check in the first 10 to 20 minutes of an outage walks through the order.
Causes from inside your property
Outside events get the blame, but a large share of everyday surges start on your own side of the meter.
Large loads switching on and off
Motors, compressors and pumps draw a heavy burst of current when they start, and they push a transient back through the wiring when they stop. The trade publication ECD notes that switching inductive or capacitive loads such as motors or capacitor banks can create oscillatory transients, and that impulsive transients can be caused by electrostatic discharge, lightning, poor grounding, inductive-load switching and utility fault clearing.
At home, that means the usual suspects: ducted and split-system air conditioners, fridges, pool pumps, bore pumps, washing machines and workshop tools. If your lights dim or flicker each time the aircon kicks in, that is a symptom worth chasing. We cover the likely faults in 5 faults that make lights flicker when the aircon starts.
Overloaded circuits and power boards
A circuit asked to carry more than it was designed for runs hot, and its connections degrade. Stacking double adaptors on a single outlet is the typical culprit. Overload does not create a surge by itself, but it creates the loose, hot, intermittent connections that do. If a breaker keeps tripping, read 4 causes of circuit breaker trips and when to call before you keep resetting it.
Faulty or damaged wiring
Loose terminals, damaged insulation, rodent-chewed cable and corroded connections cause arcing and unstable voltage. Safe Work Australia says electrical faults, arcing or explosions can cause fires, and that shocks can cause burns, heart damage or death. Coastal air accelerates corrosion, so older homes near the bay are worth a closer look.
One hidden example is reversed active and neutral wiring at an outlet, which leaves things live when you think they are off. See reverse polarity outlets for how that happens.
Poor earthing
Earthing is the path that carries unwanted energy away. When it is weak or missing, a transient has nowhere safe to go and it goes through your equipment instead. Poor grounding is one of the causes of impulsive transients listed in the ECD article above. Surge protection devices rely on a good earth to do their job, which is why we wrote check earthing first: home surge protection for Mornington Peninsula homes.
Constant high voltage is not the same as a surge
Some properties do not suffer spikes at all. They just run a little high all the time, and lights burn out early or electronics die young. This is a different problem with a different cause.
Energy Networks Australia explains that distributors may supply customers close to a substation or pole-top transformer at the higher end of the allowable range so customers farther along the line stay above the minimum, particularly at peak times. It adds that voltage varies with feeder length and distribution-transformer tap settings. Houses near a transformer can therefore sit high without anything being wrong inside.
Sags are the opposite event. The same industry body's customer guide lists distribution and transmission faults, large-motor starting and transformer energisation inrush as causes of voltage sags. Sags are not surges, but they often turn up in the same disturbance, so a flicker can be both.
If you suspect sustained high voltage, an electrician can log it with a meter over a few days. Do not guess, and do not adjust anything on the supply side yourself: that belongs to the distributor.
Signs your property has had a surge
Surges are often invisible. Look for patterns:
- Appliances that die together after a storm or outage, especially those with standby lights or digital displays.
- A power supply, charger or LED driver that fails every few months.
- Clocks and timers resetting for no clear reason.
- Outlets that buzz, feel warm or show scorch marks.
- Lights that flicker or surge in brightness when a large appliance starts.
- A smell of burning plastic near the switchboard or an outlet. Treat that as urgent: switch off at the main if it is safe to do so and call an emergency electrician.
One dead gadget after a close lightning strike is bad luck. Several failures over a year with no storm points to the building itself.
Homes, businesses and care facilities face different risks
Homes
Residential surges mostly come from storms, outages and big appliances. Solar and battery systems add more electronics to protect, so they are worth including when you review protection. The electrical safety checklist for homeowners is a good starting audit.
Commercial sites
Businesses add a lot of internal sources. Munich Re's commercial building guide says disturbances often come from internal sources or neighbouring businesses, including copiers, air conditioners, elevators and variable-frequency drives. It also says the risk rises with poorly maintained electrical systems, failed surge protection, concentrated electronic equipment, excessive current on grounding conductors or neutrals, and frequent backup-power switching.
That last point matters for any site with a generator. Every changeover is a switching event, and a poorly installed changeover switch makes it worse. Our cost guide for a generator changeover switch in Australia explains what a proper install involves.
Supply type matters too. A site running heavy three-phase motors has a different load profile from a house on single phase, and a clear explanation of three phase versus single phase power helps you understand why imbalance and large starting loads show up as flicker and nuisance faults.
Aged care, retirement villages and disability accommodation
Here the consequence of a failure is not a dead television. It is a nurse-call system, a lifting device, a medication fridge, a door-access controller or an oxygen concentrator going down. Safe Work Australia says employers and contractors must manage electrical risks through an ongoing risk-management process. For a facility manager, that means treating surge protection, earthing checks and testing of backup supply as scheduled maintenance, not as something to sort out after an incident.
Reducing the risk
You cannot stop lightning, but you can limit what it does.
- Unplug during storms and outages. The Queensland Electrical Safety Office advises avoiding sensitive electrical equipment and fixed-line phones during storms. Energy Safe Victoria advises disconnecting during power failures.
- Use surge protectors where they fit. The same Queensland guide says surge protectors help extend the life of electrical equipment. It also warns not to confuse them with safety switches. A surge protector guards equipment. A safety switch guards people. See why electrical safety switches trip.
- Consider protection at the switchboard. A device installed by a licensed electrician at the board covers every circuit, and a plug-in board then handles what gets through. Protection only works with sound earthing, so have that checked first.
- Fix the faults that generate surges. Loose terminals, damaged cables and overloaded circuits need repair, not protection.
- Consider lightning protection for exposed buildings. Standards Australia says AS 1768:2021 specifies requirements for lightning protection for structures and for the electrical and electronic systems within them. It is mainly relevant to larger or exposed sites.
- Use a licensed electrician. Electrical work in Victoria is for licensed people, and that includes installing protection at the board.
Our perspective
Most surge calls we get are not about the surge. They are about what the surge revealed. A client replaces a dead pool-pump controller, then another one six months later, and the real cause is a corroded neutral or an earth that was never right. Buying a bigger surge protector over that is spending money to hide the fault.
Our approach is to look at the whole supply side: switchboard, earthing, circuits feeding big motors, and the heating and cooling equipment that creates the switching loads. Because we work across plumbing, electrical and heating and cooling, we can see how a failing compressor or pump feeds back into the wiring, rather than blaming the network by default.
For care sites we recommend putting surge and earthing checks into a maintenance schedule, so critical equipment is covered before the next storm and not after it. Nobody wants a call at 2 am to a facility with a failed system, and we run emergency availability around the clock for exactly that reason. The cheaper job is always the one done before the failure.
— Mike
Get a surge and earthing check on the Peninsula
DualFlow Services provides electrical, plumbing, heating and cooling and hot water services, scheduled maintenance and compliance checks for homes, businesses, aged care, retirement villages and disability care homes across the Mornington Peninsula and surrounding Melbourne suburbs. If you are losing electronics, seeing flicker or planning protection for a facility, our electrical team can inspect the board, earthing and circuits and tell you what is causing it.
If something smells burnt or an outlet is scorched, do not wait for a booking. Our emergency call-out covers that, and our home page lists how to reach us. For the common emergency scenarios and what to do first, read types of emergency electrical situations.
FAQ
What causes most power surges at home?
Inside the home, the most common triggers are large appliances cycling on and off, overloaded circuits and faulty wiring. From outside, lightning, damaged powerlines and transformers, and network switching are the main sources. Which is most likely depends on how often your appliances fail and whether failures follow storms.
Can a power outage cause a surge?
The outage itself does not, but restoration can. When supply returns, conditions can change suddenly. Emergency Victoria and Energy Safe Victoria both advise switching off or unplugging appliances during an outage, then reconnecting once supply is steady.
Is a power surge the same as a voltage spike?
In everyday language, yes. Power Quality Australia says transient overvoltages are also called surges or spikes. Engineers describe them by waveform: impulsive transients are fast peaks, and oscillatory transients ring and fade.
Does a surge protector stop all surge damage?
No. A surge protector helps extend the life of equipment, but it does not replace good earthing, sound wiring or a safety switch. A very close lightning strike can overwhelm a plug-in board, so unplugging during severe storms is still the safest step for valuable electronics.
Why is my house voltage always high?
It may not be a surge. Homes close to a substation or pole-top transformer can be supplied toward the upper end of the allowed range, and feeder length and transformer settings also affect voltage. An electrician can log your voltage over several days, and if it is out of range the distributor is the party to contact.
Sources
- Power surges, Ausgrid
- Electricity in the home, Queensland Electrical Safety Office
- Transient overvoltages on the electricity supply network, Power Quality Australia
- Power outages, Emergency Victoria
- Electrical emergencies, Energy Safe Victoria
- Understanding the most common power quality problems, ECD
- Is too much solar to blame for voltage issues?, Energy Networks Australia
- Customer guide to electricity supply, Energy Networks Australia
- Electrical hazards, Safe Work Australia
- Power quality of commercial buildings, Munich Re
- AS 1768:2021, Standards Australia
- Three phase vs single phase power