Glossary
Quick definitions
Every underlined term on this site links back here. Jump straight to one below, or skim the lot.
- AEMO
- The Australian Energy Market Operator. A government-established body that runs the National Electricity Market, dispatching generation every 5 minutes to match supply with demand.
- Controlled load
- A separately metered circuit (commonly for hot water systems) that a distributor can switch on only during off-peak hours, in exchange for a cheaper rate.
- Demand charge
- A charge based on your highest rate of electricity draw (kW) during a billing period, rather than total energy used. More common on business tariffs than residential ones in Australia.
- Dispatch interval
- The 5-minute window in which AEMO matches generation bids to demand and sets the spot price for that interval. There are 288 dispatch intervals in a day.
- Distributor
- The company that owns and maintains the poles, wires and substations that physically deliver electricity to your property (e.g. Ausgrid, Energex, Powercor). You can't choose your distributor — it's fixed by where you live.
- Duck curve
- The shape of net electricity demand across a day once rooftop solar is accounted for: a deep midday dip (when solar floods the grid) followed by a steep evening ramp as the sun sets and demand rises. Named for its silhouette resembling a duck.
- Feed-in tariff (FiT)
- The rate a retailer pays you (as a bill credit) for solar electricity your system exports to the grid. Set by retailers within a state-regulated minimum, and often varies by time of day.
- Generator
- A company that owns power stations (coal, gas, wind, solar, hydro, batteries) and sells electricity into the NEM by bidding to supply it at a given price.
- kW (kilowatt)
- A unit of power: the rate at which energy is being used or produced at a given instant. Your solar system's size (e.g. 6.6kW) is measured in kW.
- kWh (kilowatt-hour)
- A unit of energy: 1,000 watts sustained for 1 hour. This is what you're actually billed for on the usage portion of your bill.
- MWh (megawatt-hour)
- 1,000 kWh. Wholesale electricity prices in the NEM are quoted in $/MWh, not $/kWh — divide by 1,000 to compare to your retail rate.
- NEM (National Electricity Market)
- The wholesale electricity market connecting Queensland, New South Wales, the ACT, Victoria, Tasmania and South Australia. Western Australia and parts of the Northern Territory run separate, disconnected systems.
- Off-peak rate
- The cheapest per-kWh rate on a time-of-use plan, applying outside the peak (and shoulder, if any) window — commonly overnight, though some plans define off-peak as simply 'all other times' outside a single peak window.
- Peak rate
- The highest per-kWh rate on a time-of-use plan, charged during a retailer-defined window of highest typical demand — often mid-afternoon to evening (e.g. 3pm-9pm) on weekdays. Usage during this window costs noticeably more than off-peak.
- Retailer
- The company that sells you electricity and sends your bill (e.g. AGL, Origin, EnergyAustralia). Retailers buy wholesale power from the NEM and pay distributors for delivery, then bundle both costs into your tariff. You can choose your retailer.
- Shoulder rate
- A middle per-kWh rate on some time-of-use plans, sitting between peak and off-peak and applying during moderate-demand periods (e.g. mid-morning, early afternoon). Not every plan has a shoulder rate — some use just peak and off-peak.
- Spot price
- The wholesale price of electricity in a NEM region, set every 5 minutes by AEMO based on the cheapest available generation bids needed to meet demand. Can range from below zero to the market price cap.
- Supply charge (daily charge)
- A fixed daily fee on your bill for being connected to the grid, charged regardless of how much electricity you use.
- Time-of-use (TOU) tariff
- A pricing structure where the per-kWh rate changes depending on the time of day — typically cheaper off-peak, more expensive during evening peak demand.
- WEM (Wholesale Electricity Market)
- Western Australia's separate electricity market, run independently of the NEM because WA's grid isn't physically connected to the eastern states.