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Why most content gets air conditioner costs wrong
Type "how much does an air conditioner cost to run" into a search engine and you get the same article every time: a list of unit sizes, a cents-per-hour figure, and a reminder to buy a high star rating. All of it is technically true. All of it misses the point.
Those guides multiply your unit's power by a single average rate. But almost no Australian household pays a single average rate for the electricity an air conditioner uses. Cooling load is concentrated in the late afternoon and evening, which is exactly when time-of-use and demand tariffs charge the most. A cents-per-hour figure that ignores when you run the unit can understate your real cost by a third.
The second blind spot is the star rating. The Zoned Energy Rating Label (ZERL), which replaced the old single-star label for air conditioners in 2020, measures how efficiently a unit performs in different climate zones. It is a genuinely better label. But it assumes a fixed amount of use and says nothing about your tariff. Buying a six-star unit and running it badly on a peak-heavy plan will cost you more than a four-star unit run smartly. Efficiency is a property of the machine. Cost is a property of the system you plug it into.
How air conditioner pricing actually works
To see why timing dominates, you have to separate the three things on your bill. Your electricity charge has a fixed daily supply charge (you pay it whether the aircon runs or not), a usage charge in cents per kilowatt-hour, and on some plans a demand charge based on your single highest burst of use. Air conditioning hits all three, but it does its real damage in the usage and demand components.
The tariff structure is the hidden lever
On a flat-rate tariff, every kilowatt-hour costs the same, so timing does not matter to your bill. On a time-of-use tariff, the day is split into peak, shoulder and off-peak. The peak window, typically around 3 pm to 9 pm on weekdays, can be priced at well over double the off-peak rate. Cooling demand peaks in that exact window. That is not a coincidence, and we will come back to it.
A growing number of network areas also apply a demand tariff: a charge based on the highest half-hour of power you pull during peak times in a month. Switch on a big unit at 6 pm on the hottest day and you can set a demand peak that quietly inflates your bill for the whole billing period, long after that day has passed. This cost is invisible to anyone thinking only in cents per hour.
The regulated benchmark and who sets it
Every plan in the National Electricity Market is anchored to a reference price. The Australian Energy Regulator (AER) sets the Default Market Offer (DMO) each year for New South Wales, South Australia and south-east Queensland; Victoria has its own Victorian Default Offer (VDO) set by the Essential Services Commission. These are the safety-net prices, and they are the honest yardstick for comparing market offers. A plan advertised as "20% off" only means something measured against the DMO or VDO for your area, not against an inflated made-up rate.
This is also where the market splits in two. Retail competition exists only in Victoria, New South Wales, South Australia, Queensland and the ACT. In Western Australia households buy from Synergy, and in the Northern Territory from Power and Water, with no retailer to switch to. If you live in WA or the NT, "shop around for a cheaper plan" is not advice you can act on. Your levers are your tariff type and your timing.
Flat-rate vs time-of-use: see the gap for yourself
This calculator shows the one thing the generic guides hide: the same air conditioner, using the same electricity, costs different amounts depending only on your tariff and when you run it. Adjust your unit and habits and watch the seasonal cost move. Every figure it produces also appears in the worked example and table below, so the facts do not live inside the widget.
Air conditioner running cost estimator
Flat-rate vs time-of-use, per summer (90 days). Edit any input.
USES ABOUT kWh THIS SEASON ( kWh/day)
Assumes electricity input = capacity ÷ EER, held steady across the run. Rates are editable defaults, not your actual plan. Check your bill or a Basic Plan Information Document for real peak, off-peak and supply charges. Source for benchmarks: AER (DMO) and the Essential Services Commission (VDO).
Worked example (the calculator's default). A 5 kW reverse-cycle unit at an EER of 3.5 draws about 1.43 kW. Run six hours a day for 90 days, it uses roughly 771 kWh. Here is what that identical consumption costs under three scenarios:
| Scenario | Effective rate | Cost for the season |
|---|---|---|
| Flat rate @ 30 c/kWh | 30.0 c/kWh | ~$231 |
| Time-of-use, run 70% in the peak (48 c) / 30% off-peak (22 c) | 40.2 c/kWh | ~$310 |
| Time-of-use, pre-cooled to 30% peak / 70% off-peak | 29.8 c/kWh | ~$230 |
The unit never changed. The star rating never changed. Shifting when the cooling happens moved the seasonal cost by about $80, and turned a "bad" time-of-use plan into one that beats the flat rate.
How Australians overpay without realising it
The analysis above turns into a handful of very common, very expensive mistakes:
Many households were moved onto time-of-use tariffs when they got a smart meter, often without realising it. They keep cooling habits built for a flat rate, blasting the aircon from 5 pm, and pay the peak premium on every kilowatt-hour without ever seeing the tariff that is charging them.
People spend hundreds more on a higher star rating, then run the unit in the worst possible window. The efficiency gain is real but small next to the tariff penalty it never addresses.
A unit too big for the room short-cycles: it blasts cold, hits the target fast, switches off, then restarts. That stop-start pattern is less efficient than a right-sized unit holding a steady temperature, and it spikes demand on demand tariffs.
The single biggest missed saving. Households run ducted gas or a resistive heater in winter while a reverse-cycle air conditioner sits on the wall delivering three to five times more heat per dollar. They paid for the cheapest heater in the house and never use it as one.
The insider insight: your cooling habit designs the peak
Here is the part that rarely gets said plainly. The afternoon-to-evening peak window is not arbitrary. Networks and retailers set those windows around the hours when the grid is most stressed, and in summer that stress is driven overwhelmingly by air conditioning switching on as people get home. In effect, your cooling habit helped define the most expensive hours on your own bill.
That sounds like a trap, and on a peak-heavy habit it is. But the same mechanism is also the opening. The grid wants load moved out of that window, so time-of-use and demand tariffs are designed to reward you for doing it. Pre-cooling, dropping the temperature a degree or two in the cheaper afternoon shoulder and then coasting through the peak with the doors shut, is exactly the behaviour the pricing is engineered to encourage. You are being paid, through a lower effective rate, to do what the network needs.
The second hidden truth is about heating economics. Energy guides still casually repeat "gas is cheaper for heating." That was true a decade ago. After sustained gas price rises across the eastern states, the physics of the heat pump has flipped the maths: a reverse-cycle air conditioner running in heating mode delivers three to five units of heat per unit of electricity, while gas combustion delivers less than one unit of heat per unit of energy you pay for. The cheapest heater in most Australian homes is the box people only think of as a cooler.
What you should actually do
Each step below follows directly from the analysis, not from a generic checklist:
| Do this | Why it works |
|---|---|
| Find out which tariff you are on (flat, time-of-use or demand) | It is the single biggest driver of cost and most people do not know. It is on your bill or your retailer's Basic Plan Information Document. |
| On time-of-use, pre-cool before 3 pm and coast through the peak | Moves cooling load to the cheaper rate the tariff is designed to reward, as the table above shows. |
| Set 24–26°C cooling, 18–20°C heating | Each degree closer to the outside temperature cuts roughly 5–10% off that cycle's energy. |
| Use the reverse-cycle unit for winter heating | Three to five times more heat per dollar than gas or resistive heating in most of the NEM. |
| Size the unit to the room, do not oversize | Avoids inefficient short-cycling and the demand spikes that inflate demand tariffs. |
| In VIC, NSW, SA, QLD, ACT: compare plans against the DMO/VDO | Retail competition lets you switch to a better rate or tariff structure for your cooling load. |
If you are in Western Australia or the Northern Territory, ignore the last row. There is no retailer to switch to, so concentrate everything on tariff choice within Synergy or Power and Water, and on timing your cooling. The behaviour levers matter even more where the market lever does not exist.
Why this matters right now
Two trends make this the year to get it right. First, smart meters and time-of-use tariffs are becoming the default rather than the exception, so the timing penalty now reaches households that never opted into it. Second, as the eastern-states gas market stays tight, the cost gap between gas heating and reverse-cycle heating keeps widening in the heat pump's favour.
The takeaway is simple to state and easy to act on: your air conditioner's running cost is mostly a decision, not a fixed fact. The unit sets a floor. Your tariff and your timing decide how far above that floor you land. Understand the structure behind the meter, and you control the bill instead of being surprised by it.
Frequently asked questions
Current figures — last updated 2026-06-13
All values in AUD and Australian units. Volatile figures change; check your own plan before relying on them.
| Electricity drawn by a 5 kW reverse-cycle unit | ~1.4 kW (capacity ÷ EER, EER ≈ 3.5) |
|---|---|
| Heating efficiency of a reverse-cycle unit (COP) | 3–5 units of heat per unit of electricity |
| Typical flat usage rate | ~25–35 c/kWh [verify: your plan] |
| Typical time-of-use peak rate | ~40–55 c/kWh [verify: your plan] |
| Typical time-of-use off-peak rate | ~18–25 c/kWh [verify: your plan] |
| Typical weekday peak window | ~3 pm–9 pm [verify: your network] |
| Recommended set point | 24–26°C cooling · 18–20°C heating |
| Energy change per degree | ~5–10% per °C |
| Reference price (NSW, SA, SE QLD) | AER Default Market Offer, reset annually [verify: current DMO for your zone] |
| Reference price (VIC) | Victorian Default Offer, set by the ESC [verify: current VDO] |
Sources: Australian Energy Regulator (DMO), Essential Services Commission Victoria (VDO), Zoned Energy Rating Label (ZERL) scheme, manufacturer specifications. State-by-state retail competition: AER / state regulators.