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Mains electricity: undervoltage and overvoltage



Have you had any issue with the electricity supply to your home not being of acceptable voltage ?

For the purposes of this survey, I’ll define acceptable as per the relevant Australian standard (AS 60038-2012): between a low limit of 216V and an upper limit of 253V. ( This is for single phase, 2-wire connections. If you had an issue with other supply types, I’m also interested, but don’t want to confuse things with too many figures )

I’m only interested in problems due to the grid / power network infrastructure, not one-off sudden spikes or sags due to lightning strikes, cars crashing into power poles, etc.

Did you have any appliance(s) damaged as a result ?
Did you seek compensation for the damage - from your insurer ? from your provider ?
Who is your network provider (if you know), or who is your retailer in which state or territory ?
Was the problem with the voltage a long-term one, or only relatively brief ?
How quickly after the problem was reported was it resolved ?
Do you have a rooftop solar system, and did the issue prevent your system from exporting electricity to the grid ?

Thank you in anticipation !



Scott, How are consumers going to be able to determine what the minimum and maximum supply voltage is, without resorting to using a recording voltmeter?.
Yes, you can make random measurements with a voltmeter, but this will not indicate maximum and minimum voltage over a period of time.
In order to make a complaint to your electricity supplier, you would probably need documentary evidence of variations outside of the accepted standard, I would think.


You are correct, Airsie, in that anyone that wants to know will need to use a voltmeter of some description. This might be incorporated in an existing smartmeter, solar system inverter, energy consumption monitor, outlet tester… there are a number of alternatives.

The issue that we are particularly interested in is where a property is supplied with mains electricity that does not conform to the Australian standard, for an extended period of time. We’re not interested in sudden spikes or sags in supply (unless they are frequent and on-going). For example, if you were to measure your supplied voltage at four different times on one day, and each time it was greater than 253V, then you would have ample cause for suspicion.

In such an event, particularly in suburban areas, more than one household can be affected, and simply the evidence of damaged appliances from a number of neighbours may be sufficient to make a claim on the supplier.


I believe once you make a complaint, your electricity retailer installs a data logger to keep track of the voltage fluctuations, before deciding on whether they will do anything about it.
A lot of the problem is due to undersized transformers and cabling, so they jack up the winding voltage on the transformer a bit to compensate for high load periods, in order to keep the voltage above the mandated minimum. This can cause problems when one or more PV systems are installed in an area serviced by one of these undersized transformers or cabling, forcing the voltage to go high. I understand they limit the size of PV systems in some areas, and wont allow them at all in some areas, due to this problem.


I believe that most hardware will cope with between 240 and 250 VAC. This is not a hard requirement. Switching supplies like those on Laptops just cope due to the way they are configured. Hard supplies like desktop computers are problematic in this area. Over and undervoltage is mainly an issue in the country where long runs of cable exist.

If you have sensitive equipment it should be protected anyway. Using a surge protector is a very good idea for any electronic device. Especially if you are in an area where lightning strike may hit power polls or telecom equipment. It has happened to my brother and a lightening strike on telstra equipment fried his modem and through the wired network cables other equipment. He now uses a more protected environment. He is in a small property outside of town. I live in the city and I have never used any protection. I have had one modem die in many years of use but I am uncertain whether it was strike or not.

As computers become more prevalent (eg TV and video recorders) there will be more issues. Just try and keep things simple if you are too far from a large centre.


Our problem happened around 15 years ago we often noticed our microwave oven would operate but not actually cook anything in the evenings from around 5.45 to 7pm all other times it was OK, so suspecting it was a voltage drop issue during the busy evening peak and being a technically trained person I used my voltmeter next time it happened and measured line voltage at lower than 200V during this problem period.
We complained to the local power supplier and they came out and ultimately switched our connection to another phase.
The workman advised there was too many people in our street on the same phase.

Since the work it has never happened again.
BTW still have the microwave a 33 year old National ( panasonic) model that choice recommended at the time.


We live in suburban Brisbane and haven’t known of any appliances fail due to low or high voltage. I thought I would check our solar inverter to see what it has recorded as the Vmax and Vmin over the past 6 years. Assuming that the inverter is reasonably accurate, the recorded Vmax was 263V and Vmin 221V.

I know that the electricity industry has had concerns of the impact of large number of solar feed-in systems on a local network and impact on these on network voltage. It is also difficult for the network operators to buffer these voltage troughs and spikes through hardware such as static var compensators or capacitor banks…as these are at substations and not attached to street transformers where majority impacts of feed-in systems occur.

There are also problems at network extremities (users a long way from substations) has they can have significant voltage drops due to distance and network usage.


We are in a rural area on a SWER line and accept that it is never going to be 100%. Our sensitive equipment has surge protectors, but we can’t protect our lights and frequently change bulbs. By frequently I mean - two in the last 3 days, at least 1 a month; tried halogen, LED, standard, dimmable, long-life. 3,000 hour lasted a fortnight. Don’t know what the voltage is doing.


Hi Scott: I believe this is a very technical issue that the average person would not understand. I suspect they may recognise a problem with the electricity supply without having any awareness of over or under voltage.
These problems have quite different mechanisms of causing failure, but the outcome is a piece of electrical equipment (appliance) will fail - sometimes catastrophically!
The most likely cause of over and under voltage is where a house is on a feeder (wire). Houses close to the substation (transformer) will be the most likely to experience over voltage, while houses at the end of a feeder will be the most likely to experience under voltage. The time when problems occur are also quite different: over voltage will be more likely in the middle of the night when everything is turned OFF; and under voltage is most likely in the afternoon peak, when everything is turned ON - especially on particularly hot or cold days!
The voltage problems were addressed by electricity authorities by installing bigger (upgrading) transformers and feeders (wires). This upgrading extended all the way through the electricity system so that it could cope with the the really big demands that occur only about 7 to 10 days a year. This process was pejoratively refereed to as “gold plating”, but has resulted in a very reliable electricity system - some argue that it is “too reliable” so the cost was too high!
So, for those still reading, if you are really concerned about your voltage you can arrange for your electricity provider to fit a data logger to monitor your supply, but don’t expect anything to be identified! OR, if you are really keen, you can install your own electricity monitoring system so you can track all your electricity data all the time.
Finally: 1) The ac output voltage reading for solar panels is not a good guide as this voltage has to be higher than the supply voltage for it to work (unless it is over 260-volts, then there may be a problem). 2) Surge protectors will not help, the reason is in the name, i.e. “surge”, which is very short time rise in voltage (microsecond); what is being discussed is very long periods!
Disclaimer: I worked for an electricity supply authority in NSW for over 15-years, I am now retired!


Hi zackirii: Your problem is probably outside the scope of what Scott is asking, but you probably actually represent a microcosm of both over and under voltage issues combined!
For those reading this and not sure what “SWER” is, it stands for “Single Wire Earth Return”, which is used in remote rural properties with relatively small power demand. The big cost for electricity due to distance; a lot of poles (no underground here) and long lengths of wire are needed. This is overcome in very remote properties by running one wire (there is no return wire, the ‘earth’ is the return path) so half the wire cost; this one wire is lighter than two so poles do not need to be a strong. To allow the poles to be separated by very long distances the wire has a steel core - aluminium wires tend to sag too much - so even less poles. The downside is that for small wire sizes they end up more like a piece of fencing wire and not a good conductor.
Now all the things that make having SWER attractive end up creating the problem Zack is experiencing. Long distance and wire size are the enemies of voltage, so there can be huge voltage fluctuations depending on what is turned on. This will probably be exacerbated by the transformer at the property, which is most likely quite small capacity so that as the demand reaches the upper limit it just does not cope (I won’t go into detail) so very low voltages. Of course, during times when not much is turned on, there will be very high voltages resulting in things burning out!


  1. Talk to you electricity supply authority about having your supply upgraded. This will be very expensive and there will still be reliability problems - wires will still fall off poles and poles fall over! It may be that the transformer is too small or the voltage set too high? so it may be a matter of minor adjustments.
  2. Install solar panels, a wind generator (check how noisy it is though) and maybe even a battery system. This will be very expensive, but could be more reliable and possibly les expensive than the long run of wire. Whether you go full self sufficiency (off grid) is something to consider on the grounds of cost and overall reliability. If you do stay ‘on grid’ you would need to have the transformer readjusted anyway.

Hope this helps


In my experience, going off-grid results in a huge increase in reliability- no more blackouts, which sometimes last a day or 2 around here (or so the neighbours tell me!), every time there is a bit of wind with a storm. Of course, you become responsible for equipment maintenance etc, but big voltage fluctuations will no longer be a problem, so devices currently being killed by fluctuating mains voltages will last much longer.

Back in the 1980s in some remote areas of Tasmania, some SWER lines were hung off insulators mounted on trees! Maybe they still are…


I used to live in a remote country town in Victoria. There was a small ‘sub-station’ a couple of kms down the road. When a power fault occurred this would trip and we would have no power. The electricity company would come out (quite a few km) and reset everything and we were back on line. When privatisation occurred the sub-station was disabled. Any faults then affected the town supply and would drop the voltage to around 140v. I can remember watching my DVD deck come out, go in, come, go in as the voltage was too low. The phone system at work burnt out. The new company replaced it - twice at high cost. They thought they were saving money by not having the guys have to come out and reset the sub-station. It soon went back on-line! I monitored the voltage whenever we had problems and it was always low.


Hi @ScottOKeefe

We are near the end of a spur line off a local substation in an urban environment.

About four years ago we noticed that our rooftop PV system was producing, but not exporting to the grid. As it was under warranty I called out the installers. They came out in under two weeks and checked the system. No fault was found, and they suggested I contacted Energex the local power supplier (Origin is our retailer).

Energex people came out another week or so later and determined that the voltage outside was too high (I think) for the inverter to send out electricity.

Adjustments were made at the local substation, and then like magic, we were exporting power again. If I remember correctly, we lost about three months of summer output from the time the inverter logs showed the first problem to when it was all working again.

No compensation was offered, and I didn’t know we could ask for any.

Earlier this year, we were having sporadic ‘brown-outs’ with our lighting (a mixture of mainly LED, fluoro, and standard lights) dimming for short periods, issues with an installed disabled lift, and other appliances misbehaving. Thinking this was due to fluctuations in the voltage I called up Energex again. Because we are registered with them for life saving equipment, their staff were out the next day. They checked our connection to the power pole and made sure there were no issues with the sub-board/fuse box.

They told me they had to arrange a data logger and came back in under a week later with one which they left connected to one of our power circuits for over a week.

I can’t remember the exact voltage parameters they used (I think it may have been similar to what you quoted from AS 60038-2012), but they could not see any unacceptable over or under voltages, even though we still had lights dimming etc.

They could offer no cause on their system, but suggested that perhaps one of the increasing number of PV systems on our spur line may have something to do with what was happening.

Interestingly, the brown-outs disappeared soon after.


An interesting article regarding problems with the voltage of mains power.

Anyone with a multimeter may wish to measure the voltage at their premises as long as they do so safely.

We were taught that the mains voltage in Australia was 240 volts so the statement that the standard is actually 230 volts is surprising.


It changed in 1980 as part of an international harmonisation project. Many people would share your surprise. I can see many a dispute at trivia nights around Oz over this question.


Misinformation and assumption and a warning!

There are significant safety risks with attempting to measure the mains using a multimeter. Don’t do it. There will be a few Choice readers who are aware of the issues and know what is required to do so safely. Most cheaper multimeters are not safe to use on mains!

JCar and others sell 240v plug in meters that are the safe way for 99% of us consumers to use.

The ABC new report is also very poorly written and misleading in some aspects? I’ll comment later.


I am both qualified and experienced to safely measure the mains voltage and I do so by simply pushing the probes of my Fluke 12 multimeter into the active and neutral entries of the power point.

I expected that there would be others not experienced to measure the mains voltage which is why I said “as long as they do so safely”.

I just measured our mains voltage which is currently 246.2 volts.


Yes, a good one for trivia nights. There is a difference between what we might have agreed to as a nation and actual state practice. You might get a whole night out of this topic. :grin:

Refer to this link if you choose: Qld household supply was still legally 240v +/-6% up until Oct 2018, and has a transition period until 2020 to the new standard of 230v +6% -2%. :zap:


@Fred123 It may be very apparent to you and I what is necessary to directly measure the mains voltage safety. I would choose to not share this knowledge in general and to suggest others not attempt it.

The community knowledge is limited by what is not common or everyday. Many of the wider community may not be able to make correctly the judgement call as to what safe is, and wrongly assume that it is safe to work with electricity with the knowledge they have.

It would be wise for anyone before they do any electrical work to also consider the specific directions of the relevant Electrical Safety legislation and regulations in each state. Unfortunately there are many everyday multimeters around that are not safe to use for the task, more so if the user does not understand or appreciate fully the hazards and risks.

Rather than discuss the requirements for prescribed work or make a long list of requirements including IEC 61010 Cat ratings for meters etc, it may be simpler to advise against the practice.