Air conditioner running cost calculator: methodology
The formula
Cost per hour = input power (kW) × duty factor × tariff ($/kWh). Input power is what the unit draws from the wall, not its cooling capacity: a 5 kW split typically draws about 1.36 kW. The duty factor (default 0.65) reflects that an inverter throttles back once the room reaches temperature; drag it to 1.0 for a scorching afternoon with the doors open, or 0.4 for overnight in a closed bedroom.
Cost per day = cost per hour × hours. Cost per period = cost per day × days. A second mode uses the annual kWh printed on the Zoned Energy Rating Label for your zone (hot, average or cold) multiplied by the tariff — that is the official annual figure and needs no duty assumption.
Default tariffs by state (from 1 July 2026, incl. GST)
| State | Default rate (c/kWh) | Daily supply (c/day) | Basis |
|---|---|---|---|
| NSW (Ausgrid) | 33.14 | 166.23 | AER DMO 2026–27 tariff cap |
| QLD (Energex, SE Qld) | 27.97 | 192.02 | AER DMO 2026–27 tariff cap |
| VIC (average of five zones) | 28.20 | 127.00 | ESC Victorian Default Offer 2026–27 |
| SA | 41.91 | 180.05 | AER DMO 2026–27 tariff cap |
| WA (Synergy A1) | 33.26 | 119.24 | Regulated tariff, +2.75 % on 2025–26 (secondary confirmation) |
| TAS (Aurora T31) | 27.95 | 167.68 | OTTER-approved standing offer |
| ACT | 36.90 (all-in, derived) | — | ICRC typical bill $2,400 ÷ 6,500 kWh |
| NT (Jacana) | 31.68 | 62.45 | NT Electricity Pricing Order |
Regional NSW (Endeavour 33.73, Essential 35.01) and regional Queensland (Ergon 28.90) are selectable. Regulated caps are the standing-offer maximum; market offers usually sit 3–10 c/kWh lower, so a bill rate beats the default.
Input power by unit size
| Cooling capacity | Input power (cooling) | Source |
|---|---|---|
| 2.5 kW | 0.65 kW | CHOICE small-class average; Solar Choice 0.7 |
| 3.5 kW | 0.90 kW | interpolated |
| 5.0 kW | 1.36 kW | CHOICE medium-class average |
| 6.0 kW | 1.70 kW | Solar Choice |
| 7.1 kW | 2.00 kW | interpolated |
| 8.0 kW | 2.30 kW | Solar Choice; CHOICE large-class 2.15 |
| 9.4 kW | 2.70 kW | interpolated |
For your exact model, use the "rated power input" on its Energy Rating registration or the Zoned Energy Rating Label kWh.
Limitations
There is no official duty-cycle figure for inverter units; the 0.65 default is a working assumption and is adjustable. The daily supply charge is excluded by default because you pay it whether or not the air con runs. Controlled-load and time-of-use tariffs are not modelled beyond the flat rate.
Test vectors (for the build)
| Inputs | Result |
|---|---|
| 5 kW unit, NSW Ausgrid 33.14 c, input 1.36 kW, duty 0.65, 6 h | $0.293/h, $1.76/day |
| 2.5 kW unit, SA 41.91 c, input 0.65 kW, duty 0.65, 8 h, 90 days | $0.177/h, $1.42/day, $127.44/period |
| Label mode: 620 kWh/yr, VIC 28.20 c | $174.84/yr, $14.57/month |
Data tables: au-tariffs.csv, aircon-input-power.csv (CC BY 4.0).
Sources and manuals checked
Data tables: data/au-tariffs.csv, data/aircon-input-power.csv. Tariffs checked 28 August 2026; next check due 1 July 2027 or when a regulator publishes a mid-year change.
- AER — 2026–27 Default Market Offer, Final determination (26 May 2026): tariff caps NSW, SE Qld, SA (authority)
- Essential Services Commission — Victorian Default Offer 2026–27 tariff tables (authority)
- Aurora Energy — Standing Offer Price Schedule 2026–27 (OTTER approved) (authority)
- Jacana Energy — Residential pricing and tariffs 2026–27 (official)
- Ergon Energy — Residential tariffs from 1 July 2026 (official)
- ICRC (ACT) — Retail electricity price recalibration 2026–27 (authority)
- CHOICE — Air conditioner energy usage and running costs (16 Apr 2024): input power by size class (authority)
- Solar Choice — Running cost of air conditioners (input power by capacity) (secondary)
- Energy Rating — Questions and answers about the Zoned Energy Rating Label (Dec 2022) (authority)