Electricity cost calculator

Two ways in: the annual kWh printed on an energy rating label, or the power rating in watts and how long the appliance runs. Either way the result is kWh a year × your electricity price in c/kWh, in NZD.

Where to find the numbers

Label kWh is on the energy label or the product information sheet. A power rating in watts is on the rating plate, usually on the back or base of the appliance, or in the manual. Your electricity price is the unit rate on your bill (c/kWh); on a time-of-use tariff use the rate that applies when the appliance mostly runs.

What the figure is based on

33c/kWh is an example rate, not a recommendation. A rating plate gives maximum power draw; heaters with thermostats and appliances with standby modes draw less than that for much of the time, so hours of use should be hours actually running at that power.

What changes the cost

• Rating-plate watts are the maximum draw. Thermostats, variable-speed motors and eco modes mean many appliances run well below it for most of the time.
• Standby draw adds up over a year: a few watts around the clock is 20–40 kWh.
• Time-of-use tariffs: the same kWh costs different amounts by time of day; use the rate for when the appliance runs.
• Hours of use is the biggest lever. Doubling the hours doubles the cost; the rating cannot be changed.
• Label kWh figures assume standard test conditions and usage patterns; real households sit above or below them.