Peak vs Off-Peak Usage Calculator
Compare your electricity cost under a flat tariff versus a time-of-use tariff with separate peak, shoulder and off-peak rates.
Your results
Calculation breakdown
- Time-of-use cost
- Cost = (peak kWh × peak rate) + (off-peak kWh × off-peak rate)
- Flat cost
- Cost = total kWh × flat rate
Worked example
With 300 kWh at 45c/kWh peak and 500 kWh at 20c/kWh off-peak, time-of-use costs about $235, versus $240 on a flat 30c/kWh rate, so time-of-use is cheaper here.
Assumptions
- Shoulder rates are not modelled separately; add them to peak or off-peak as best fits your plan.
- Excludes daily supply charges, which are usually similar between plan types.
- Actual peak/off-peak hours are set by your network or retailer.
How this calculator works
Enter your estimated usage split across peak, shoulder and off-peak periods along with each rate to calculate your time-of-use bill, then compare it against a flat single rate. This helps decide whether shifting usage to off-peak hours, such as running appliances overnight, would save money.
Frequently asked questions
What counts as peak time?
Peak periods are set by your retailer or network, commonly weekday afternoons and evenings; check your bill or plan for exact hours.
How can I shift usage to off-peak?
Running dishwashers, washing machines, pool pumps and EV charging overnight or midday (for solar users) can reduce peak usage.
Is time-of-use always cheaper?
Only if a meaningful share of your usage happens outside peak hours; households using most power in the evening may pay more on time-of-use.
Actual prices, usage, efficiency and savings vary by provider, equipment, location and behaviour.