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Electrical

Electricity Cost Calculator

Daily, monthly and annual running cost of an appliance.

Your measurementsEvery assumption editable01
Running costCalculated live02

Result

$28.8per month

180 kWh — $350.4 a year

Power
1500 W
Daily use6 kWh
4 hr
Monthly consumption30 days
180 kWh
Daily cost
$0.96
Monthly cost
$28.8
Annual cost2190 kWh
$350.4

Nameplate wattage is the maximum draw, not the average. Anything thermostatically controlled — a fridge, a freezer, an electric heater — cycles on and off, so its real consumption is a fraction of nameplate times hours.

Many tariffs are tiered or time-of-use rather than flat. If yours charges more above a monthly threshold or during peak hours, the marginal rate for additional use is higher than the average rate on your bill.

Standby draw is missing here and is not trivial across a household. A device pulling a couple of watts continuously costs more over a year than one pulling a hundred watts for a few minutes a day.

Wattage, hours and your rate give the running cost. The trap is nameplate wattage — anything thermostatically controlled cycles on and off, so its real consumption is a fraction of nameplate times hours.

Why use this tool?What it does differently03

Why use this tool?

Three timeframes

Daily, monthly and annual, since the annual figure is usually the one that changes behaviour.

kWh shown

Consumption alongside cost, so you can check it against your bill.

Cycling flagged

Fridges and heaters cycle. Nameplate times hours overstates their real consumption substantially.

Tariff caveat

Tiered and time-of-use tariffs mean your marginal rate can exceed your average rate.

How this worksThe method04

How this electricity cost calculator works

Watts times hours divided by a thousand gives kilowatt-hours per day. Multiplying by days and by your rate gives the cost, and the annual figure extrapolates over 365 days.

Nameplate wattage is maximum draw, not average. Anything thermostatically controlled — a fridge, freezer or electric heater — cycles on and off, so actual consumption is well below nameplate times hours. For those, use an estimated duty cycle rather than full hours.

Many tariffs are tiered or time-of-use rather than flat. If yours charges more above a monthly threshold or during peak periods, the marginal rate for additional consumption is higher than the average rate on your bill.

How to use itStep by step05

How to use it

  1. Step 1: Find the wattage

    From the appliance nameplate or label.

  2. Step 2: Estimate real hours

    For cycling appliances, use effective running hours rather than hours switched on.

  3. Step 3: Enter your rate

    From your bill, in cents per kWh. Use the marginal rate if your tariff is tiered.

  4. Step 4: Look at the annual figure

    It is usually the number that makes the decision.

Example usageWorked figures06

Example usage

A space heater
1,500 W for 4 hours a day at 16 cents costs $0.96 a day, $28.80 a month, $350.40 a year.
A fridge
150 W nameplate but cycling roughly a third of the time — enter 8 effective hours rather than 24. That gives $0.19 a day, about $70 a year.
Standby draw
A 3 W device left on permanently costs about $4.20 a year. Trivial alone, but a household has dozens.
Frequently asked questionsCommon questions07

Frequently asked questions

How do I calculate what an appliance costs to run?

Watts times hours divided by 1,000 gives kWh. Multiply by your rate per kWh. Watch out for cycling appliances, where nameplate wattage overstates real consumption.

Why is my calculated cost higher than my bill suggests?

Usually because the appliance cycles. Fridges, freezers and thermostatically controlled heaters run only part of the time they are switched on.

What is a typical electricity rate?

It varies enormously by region and tariff. Check your bill rather than assuming — and if your tariff is tiered, use the marginal rate for additional consumption.

Does standby power matter?

Cumulatively, yes. A single device pulling a few watts continuously costs a few dollars a year, but a modern household has dozens of them.

How do I work out effective hours for a fridge?

Estimate its duty cycle — most run roughly a third of the time — and use that fraction of 24 hours. A plug-in energy monitor gives a far more reliable figure.

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