Electricity cost calculator

What the result means

Electricity bills charge for energy in kilowatt-hours. An appliance’s wattage tells you how fast it uses energy; time tells you how long. Cost is energy times your usage rate, not the daily supply charge.

How it is calculated

kWh = (watts ÷ 1,000) × hours. Cost = kWh × (cents per kWh ÷ 100)

• Watts: Instantaneous power drawn while the appliance is on.
• Hours: Duration of one use.
• Uses per week: Scaled to daily (÷ 7), monthly (annual ÷ 12) and annual (× 52).

Power in kilowatts times time in hours is energy. Multiplying by the tariff in dollars per kWh is cost. Weekly uses are the bridge from a single cycle to a yearly estimate.

Worked example

A 2,000 W kettle, twice a day

The kettle draws 2,000 W and boils for 12 minutes (0.2 h), twice a day, at 32 c/kWh.

Energy per boil

2 × 0.2 = 0.4 kWh

Cost per boil

0.4 × $0.32 = $0.13

Weekly

14 boils × $0.13 = $1.79

Annual

About $93

Small appliances look cheap per use and still add up. The same method works for heaters, dryers and pool pumps — just change the watts, hours and weekly uses.

Reading a bill

Most Australian residential bills have a daily supply charge plus one or more usage rates in cents per kilowatt-hour. This calculator only uses the usage rate. Standing charges continue even if the appliance is off.

Controlled-load hot water, solar feed-in and time-of-use tariffs change the effective rate by hour. Use the rate that applies when the appliance actually runs.

Questions