โก Electricity Cost Calculator
โ Life & LivingThat heater, gaming setup or lamp doesn't just have a power button โ it has a running cost. Enter how much power it uses, how long you use it and your electricity rate to see what it costs today, every month and over a whole year.
Results
So, what does it cost to keep it running?
An estimate from the power, time and price you entered โ not a quotation from your energy provider.
The cost that sneaks up over time
Which appliance is eating the most electricity?
What if you switched it off a little sooner?
Same habits. Different electricity price.
Same electricity. Very different ways to use it.
The numbers behind the estimate
| Appliance | Qty | W running | h/day | Days/wk | kWh/year | Cost/year |
|---|
These are estimates from the power, time and electricity price you entered. Appliances with thermostats, compressors or variable power draw may use less (or sometimes more) than a simple constant-wattage estimate suggests. Your actual bill can also include fixed supply charges, time-of-use rates, discounts, taxes and other plan-specific items.
The expensive part isn't always the thing you plug in.
A little lamp might be on every night and barely make a dent. A powerful heater can make its presence felt after a few chilly evenings. The difference isn't how big the appliance looks or how often you notice it โ it's how much electricity it uses, how long it's running and what your energy company charges for each unit.
That's hard to judge from a power bill. The bill shows the whole household together, while the things plugged into the wall rarely come with their monthly running cost printed on the front.
This calculator separates them out. You can compare the appliances you use, find out what that extra hour actually costs and see whether turning something down would make a meaningful difference. Sometimes the surprise is that a little change adds up. Sometimes it's that the thing you've been worrying about costs almost nothing.
Either way, the useful answer is the one with your own wattage, your own habits and your own electricity price โ not somebody else's average household.
Electricity has some sneaky party tricks
๐ก The kettle and the tiny light can tie
A 2,000 W kettle running for just three minutes uses 0.1 kWh. A 10 W LED light needs ten hours to use the same energy. At an illustrative price of $0.30/kWh, each costs 3 cents. One makes tea; the other puts in a full evening shift.
๐ป Two watts can play the long game
A gadget drawing just 2 W on standby, all day every day, uses 17.52 kWh in a 365-day year. At $0.30/kWh that's about $5.26. Not frightening by itself โ but ten identical idle gadgets could add up to roughly $52.56 a year.
๐ฅ A big wattage doesn't always mean a big bill
A 1,500 W heater used for one hour consumes 1.5 kWh. A 50 W fan would need to run for 30 hours to use that much. Power is how fast electricity gets used; energy is how much you used altogether. Runtime matters just as much as the wattage.
๐ธ A cheaper electricity rate can beat your best unplugging effort
A device using 100 kWh over a period costs $30 at 30 cents per kWh โ or $20 at 20 cents. Same device, same use, $10 difference. The little price in the corner of the bill deserves more attention than it gets.
โฐ The clock can change the price without changing the watts
Use exactly 1 kWh at a hypothetical peak price of 40 cents and it costs 40 cents. Move that same energy use to a hypothetical off-peak period priced at 20 cents and it costs 20 cents. Your appliance hasn't become more efficient. The electricity just got cheaper at a different time.
These are illustrative sums using the prices printed beside them, not average household statistics. Time-of-use periods and eligibility vary by provider and plan.
How does this electricity cost calculator work?
The short version
Electricity use is measured in kilowatt-hours (kWh). A watt (W) tells you how quickly an appliance is using power; a kilowatt-hour tells you how much electricity it used over time. Once you know the kWh, multiplying by your price per kWh gives the variable cost of running it.
Step 1: Watts to kilowatts
Power in kW = Watts รท 1,000
Example: 1,500 W รท 1,000 = 1.5 kW. If the label says 1.5 kW, the calculator converts it the same way, so 1.5 kW and 1,500 W always produce identical results.
Step 2: Energy per active day
Running energy (kWh per active day) = Power (kW) ร Hours used per active day ร Quantity
Example: 1.5 kW ร 2 hours ร 1 = 3 kWh.
Step 3: A weekly habit, annualised
Running kWh per week = (Watts รท 1,000) ร Hours per active day ร Days per week ร Quantity
Annual running kWh = Running kWh per week ร (365 รท 7)
Why 365 รท 7? It creates a 365-day annualised average for a repeating weekly habit. An actual calendar year has a different number of particular weekdays depending on its start date; this calculator estimates a typical year rather than counting exact Mondays and Tuesdays. The same factor is used everywhere, so 52 weeks never appears in one figure and 365 days in another.
Step 4: The default example, all the way through
- 1,500 W รท 1,000 = 1.5 kW
- 1.5 ร 2 hours ร 5 days = 15 kWh per week
- 15 ร (365 รท 7) = 782.142857โฆ kWh per standard year
- 782.142857โฆ ร $0.30 = $234.642857โฆ โ $234.64 per year
- Annual รท 12 โ $19.55 per average month
- Week = $4.50; each active day = $0.90
- Cost per running hour = 1.5 ร $0.30 = $0.45
Money is formatted to the currency's normal minor unit at the end. The sums above are not rounded between steps, and the total is never built by adding already-rounded per-appliance labels.
Step 5: Adding up several appliances
Total annual energy = ฮฃ each appliance's annual kWh
Total annual running cost = ฮฃ each appliance's annual kWh ร the applicable entered rate
With a single flat rate this is the same as total kWh ร rate. With a weighted peak and off-peak estimate, that one weighted rate is applied to every row, and the ranking is a ranking of energy โ under one shared rate it is the same order as cost, so the page does not pretend they are two different insights.
Step 6: Standby, if you enter it
Active hours per week = Hours per active day ร Days per week
Standby hours per week = 168 โ Active hours per week
Standby kWh per week = (Standby W รท 1000) ร Standby hours per week ร Quantity
Total kWh per year = (Active kWh per week + Standby kWh per week) ร (365 รท 7)
This assumes the device stays connected throughout the entire week, drawing the entered standby watts whenever it is not actively running. If you unplug it or power it down completely, enter 0 standby watts. A device running 24 hours a day, 7 days a week has no idle hours, so nothing is counted twice.
Step 7: Usage rates and the daily supply charge
Variable cost = kWh ร Price per kWh
Effective usage rate = (Peak share ร Peak rate) + (Off-peak share ร Off-peak rate)
Illustrative fixed supply charge per year = Daily fixed charge ร 365
Example: 60% of energy at 40 cents and 40% at 20 cents gives a weighted rate of 32 cents per kWh. At 780 kWh that is $249.60. The split is yours to enter, because the hours a device runs cannot tell the calculator which tariff window the energy fell into.
If you add a daily supply charge, it is shown separately. It is a cost of the account and connection, and it does not vanish when one appliance is switched off โ so it never joins the running-cost headline.
What the estimate does and doesn't know
The maths assumes the wattage and usage schedule you entered are representative. Real appliances don't all use power at one steady rate. Heating and cooling devices cycle on and off; refrigerators spend part of their time with compressors idle; dishwashers run different stages of a cycle; and computers change power draw depending on what they're doing. If a product label gives you kWh per cycle or kWh per year, a meter or that energy figure may be a better starting point than its maximum wattage.
Your bill may also contain fixed supply charges, taxes, demand charges, block tariffs, discounts, solar export credits and other fees. Those are not automatically included in an appliance's avoidable running cost. The price you enter should reflect your actual bill and whether tax is already included.
Assumptions worth knowing
- Power draw is treated as constant while the appliance is running; cycling devices can differ in both directions.
- A weekly pattern is annualised over 365 days, not counted against a real calendar.
- The result covers the appliances you entered. It is not a full household bill, even when a supply charge is added.
- Standby only exists when you enter a standby wattage and the device is assumed to stay connected.
- Solar exports, block or demand tariffs, discounts and plan-specific fees are outside this estimate.
- Changing the currency changes the label and number format only; it is not a currency converter.
Sources for the tariff building blocks
- US Department of Energy โ Energy Saver guide (appliance running energy and why consumption varies)
- Australian Government, Energy Made Easy โ understanding gas and electricity charges (daily fixed supply versus usage charges)
- Australian Government, Energy Made Easy โ which type of energy tariff is right for you? (flat, time-of-use and other tariff shapes)
The arithmetic is unit conversion and multiplication; these links explain the bill structures the page keeps separate. None of them supplied the example prices here.
Frequently asked questions
How do I calculate how much an appliance costs to run?
Take its wattage, divide by 1,000 to get kilowatts, multiply by how many hours it runs, then multiply by the electricity price per kWh. A 1,000 W appliance used for two hours at $0.30/kWh uses 2 kWh and costs $0.60 in usage charges.
What's the difference between watts, kilowatts and kWh?
Watts and kilowatts measure power โ how quickly electricity is used. One kilowatt is 1,000 watts. Kilowatt-hours measure the amount of electricity consumed over time. A 1,000 W device running for one hour uses 1 kWh, while the same device running for three hours uses 3 kWh.
How much does it cost to run a heater for an hour?
It depends on its actual power draw and the price on your bill. A heater drawing a steady 1,500 W uses 1.5 kWh in one hour. At an illustrative $0.30/kWh, that is $0.45 for the hour. A thermostatically controlled heater may cycle, so its real average may differ.
Is a 2,000 W appliance always more expensive than a 100 W appliance?
Not necessarily over a whole day or month. At the same rate, the 2,000 W device costs more for each hour it runs, but a short burst can use less energy than a small device left running all day. Both the wattage and the time used determine the total.
Why doesn't this calculator match my electricity bill exactly?
The calculator estimates the energy used by the devices you entered. Your bill can also reflect appliances you didn't list, time-of-use or tiered pricing, fixed daily supply charges, discounts, solar exports, taxes and other charges. Actual wattage and running hours may also differ from the estimates.
Do appliances still use electricity on standby?
Some do. A device might draw a small amount of power while waiting for a remote, staying connected to a network or keeping a display active. If you know its standby wattage and leave it plugged in, you can enter that separately so it is counted during the hours the device is not running.
Should I use the maximum watts shown on an appliance label?
It can give you a rough upper-end illustration, but it may not reflect average running consumption. Many appliances change power draw or cycle on and off. A plug-in energy meter, manufacturer energy label or actual kWh reading is often more representative.
What is a daily supply charge, and can I save it by switching something off?
A supply charge is the fixed cost of having electricity connected, even when you use very little. Switching off an appliance can reduce usage charges, but it usually doesn't remove the fixed supply charge. That's why this page keeps those costs separate.
Are peak and off-peak electricity rates the same everywhere?
No. Time-of-use periods, prices and eligibility depend on your retailer, plan and meter. If your plan has different prices, enter your actual rates and an honest estimate of how much energy falls into each period. Don't assume off-peak automatically means weekends or night-time in every location.
Can I use this calculator outside Australia?
Yes. Choose the relevant currency and enter your own electricity usage rate per kWh. The mathematics is the same worldwide. Changing the currency label does not convert money at an exchange rate, and local tax, tariffs and energy plans still need to be considered separately.
More calculators
๐ก Cozy's pick
Not sure where to go next? Let Cozy pick one of his favourites for you to try โ the lighter end of the site, picked at random, and never the one you are reading.