Single rate is the simplest electricity tariff, and is still the most common tariff used across Australia.
Single rate means that the price you'll be charged per kWh of usage will not change by the time of day or by the day of week that you use that energy.
Flat single rate tariffs
The simplest tariff of all is the flat single rate tariff where you'll be charged the same rate per kWh of usage no matter when you consumed the energy, and no matter how much you consumed over the billing period.
Stepped single rate tariffs
So called 'single rate' tariffs may not actually be single rate.
Some single rate tariffs are 'stepped rate', which means you'll pay a different price per kWh once you've crossed a certain threshold of total consumption for the billing period.