Why use this calculator
An electricity bill arrives as one number for three months, which tells you nothing about where the money went. Appliance-level costing is the only way to find out, and the arithmetic is simple enough that nobody needs a smart meter to do it: watts times hours divided by a thousand gives kilowatt-hours, and kilowatt-hours times your rate gives dollars.
Doing it properly usually overturns assumptions. Lighting and standby power feel wasteful but are small; heating, cooling, hot water and clothes drying are almost always the real bill. This calculator also separates the fixed daily supply charge from the usage charge, which matters because that fixed portion is often a quarter of a small household's bill and no amount of switching things off will reduce it.
How to use it
- Find the usage rate on your electricity bill, usually shown in cents per kilowatt-hour under consumption or usage charges, and enter it in dollars, so 28c/kWh becomes 0.28.
- Find the daily supply charge on the same page, often labelled supply, service or standing charge, and enter it in cents per day exactly as printed.
- For each appliance, read the wattage from the compliance plate on the back or underside, or from the specifications page of its manual; if only amps are given, multiply amps by your mains voltage.
- Enter the hours the appliance genuinely draws power each day, averaged across a whole week rather than a heavy day.
- Leave any appliance row at zero watts to skip it.
What each result means
- Total daily cost
- Everything the listed appliances cost in a day plus the fixed supply charge you pay regardless of usage.
- Estimated monthly bill
- The daily figure multiplied by an average month of 30.44 days, so twelve of them add up to the annual figure.
- Biggest cost on the bill
- Which single item, an appliance or the fixed supply charge, makes up the largest share of your daily cost, so you know where cutting back saves the most.
- All-in cost per kWh
- What each kilowatt hour really costs you once the fixed daily supply charge is shared across your usage. Low users pay far more per kWh than the advertised rate.
- Estimated quarterly bill
- Roughly 91 days of cost, which is the billing period most Australian electricity retailers use.
- Estimated annual cost
- The full-year cost of running these appliances plus the supply charge, useful for comparing plans or appliances.
- Electricity used a day
- Kilowatt-hours consumed each day by the appliances you entered, the same unit your meter and bill record.
- Electricity used a year
- Annual consumption in kilowatt-hours, the figure to compare against the total on your bill or against a solar system size.
- Fixed supply charge a year
- The standing charge over a year. It is unavoidable while you stay connected and is not reduced by using less power.
- Appliance 1 cost a month
- What the first appliance alone adds to a month of usage charges, excluding the fixed supply charge.
- Appliance 2 cost a month
- What the second appliance alone adds to a month of usage charges, excluding the fixed supply charge.
- Appliance 3 cost a month
- What the third appliance alone adds to a month of usage charges, excluding the fixed supply charge.
- Appliance 4 cost a month
- What the fourth appliance alone adds to a month of usage charges, excluding the fixed supply charge.
The formula
Daily kilowatt-hours = Watts / 1000 x Hours per day
- Watts
- the appliance power draw
- Hours
- its average daily running time
Daily usage cost = Daily kWh x Rate
Total daily cost = Daily usage cost + Supply charge / 100, converting the cents-per-day standing charge into dollars
Monthly = Daily x 30.44
Annual = Daily x 365, using the average month so that twelve months equals one year exactly
How this number is used in practice
Rates vary enormously by country and by plan, which is why the calculator asks for your own figure rather than assuming one. Australian residential usage rates broadly sit between 25 and 45 cents per kilowatt-hour depending on the state and the retailer, with a daily supply charge commonly around 90 to 150 cents.
United States residential prices are typically 15 to 25 US cents per kilowatt-hour and vary widely between states, and Great Britain has sat in the region of 22 to 28 pence per kilowatt-hour under the Ofgem price cap plus a daily standing charge. Treat all of those as orientation only and copy the numbers from your own bill, because a single plan can differ from the state average by a third.
The tariff structure matters as much as the rate. This calculator assumes a single flat usage rate, which is what most households are on. If your meter is on a time-of-use tariff, you will see separate peak, shoulder and off-peak rates and the same appliance costs very different amounts depending on when it runs; in that case run the calculator once per rate with the hours that fall in each window.
Controlled load tariffs, common for electric hot water and pool pumps, are billed on a separate cheaper rate entirely. Demand tariffs add a charge based on your highest half-hour of usage in the month, which no per-appliance calculation will capture.
Once you have the numbers, the decisions follow quickly. Replacing a resistive electric hot water system with a heat pump, or a vented dryer with a heat pump dryer, typically cuts that appliance's consumption by roughly two thirds, and the annual cost figure here is what you compare against the purchase price to get a payback period.
Standby power deserves a sanity check rather than a crusade: a device drawing 3 watts continuously uses about 26 kilowatt-hours a year, which is real but small compared with a single reverse-cycle air conditioner running through summer.
Worked examples
Oven 2,400 W for 1.5 hours, dryer 1,800 W for 0.5 hours and a 150 W television for 5 hours at 28c/kWh with a 110c/day supply charge
5.25 kWh a day, $2.57 a day, about $78.17 a month and $938 a year.
A single 3,500 W ducted air conditioner running six hours a day through summer at 32c/kWh
21 kWh a day and $6.72 of electricity, or $7.82 a day once the supply charge is added.
Home office: 200 W computer for 9 hours and 60 W of lighting for 6 hours at 30c/kWh
2.16 kWh a day, about $0.65 of electricity a day and roughly $19.72 a month for the two.
Electric storage hot water at 3,600 W for 3 hours a day at 25c/kWh
10.8 kWh a day and about $2.70 of electricity, close to $986 a year before the supply charge.
When people use it
- Finding which appliances are actually driving a high quarterly bill
- Comparing an old appliance against a new efficient one in dollars rather than star ratings
- Costing a home office, gaming rig or grow light before the bill arrives
- Estimating what a pool pump or electric hot water system adds each year
- Sizing a solar system against your real annual kilowatt-hour consumption
Tips
- Take the usage rate and the supply charge from your own bill. State averages can be a third away from what you personally pay.
- Heating, cooling, hot water and clothes drying are almost always the top four. Chase those before worrying about phone chargers.
- If the appliance label gives amps instead of watts, multiply amps by the mains voltage, roughly 230 V in Australia and the UK or 120 V in the US.
- Motors and compressors cycle rather than running flat out, so an air conditioner or fridge uses less than its nameplate wattage over an hour.
- The daily supply charge is unavoidable while you are connected, so compare plans on the supply charge as well as the usage rate.
- On a time-of-use tariff, run the calculator separately for peak and off-peak hours rather than averaging the rates together.
- A plug-in energy meter costs very little and will tell you the real draw of a cycling appliance far more accurately than its label.
What it assumes, and where it stops being accurate
- A single flat usage rate. Time-of-use, controlled load and demand tariffs are not modelled and will give different results.
- The appliance draws its full nameplate wattage for the whole time it is on, which overstates anything with a thermostat or compressor.
- The daily supply charge is constant and applies every day of the year, including days you use nothing.
- A month is treated as 30.44 days and a year as 365 days, so monthly figures multiplied by twelve match the annual figure.
- Taxes and levies are assumed to be already included in the rate you enter. Some bills show GST or sales tax separately.
- Solar generation, feed-in tariffs, battery discharge and pay-on-time discounts are excluded entirely.
Terms used on this page
- Kilowatt-hour (kWh)
- One thousand watts used for one hour. The unit your meter counts and your retailer charges for.
- Usage rate
- The price per kilowatt-hour of electricity consumed, shown on the bill as a usage or consumption charge.
- Supply charge
- A fixed daily amount for being connected to the grid, also called a service or standing charge. It is payable whatever you use.
- Time-of-use tariff
- A meter arrangement charging different rates for peak, shoulder and off-peak periods rather than one flat rate.
- Controlled load
- A separately metered circuit, usually hot water or a pool pump, billed at a lower rate and switched on only at set times.
Questions people ask
- Where do I find my electricity rate?
- It is on your bill under usage or consumption charges, quoted in cents per kilowatt-hour, and you enter it here in dollars, so 28c/kWh is 0.28. The daily supply charge sits alongside it. In Australia you can also compare every published offer on the government site Energy Made Easy, which lists both figures for each plan.
- What is a kilowatt-hour?
- A kilowatt-hour is one thousand watts drawn for one hour, and it is the unit your meter counts and your retailer bills. A 2,000 watt appliance running for thirty minutes uses one kilowatt-hour. A 100 watt appliance running for ten hours also uses one kilowatt-hour, which is why long-running low-power devices still add up.
- How much does an air conditioner cost to run?
- A single-room reverse-cycle unit typically draws 700 to 1,500 watts in use, so six hours a day at 30c/kWh is roughly one to three dollars daily. A ducted system drawing 3,500 watts over the same hours is closer to six dollars a day. Inverter units cycle down once the room reaches temperature, so real consumption is usually below the nameplate figure.
- Why is my actual bill higher than this estimate?
- Because you almost certainly run more than four appliances. This calculator prices only what you enter, plus the supply charge. Refrigeration, standby loads, hot water and heating run constantly in the background, and bills can also carry metering fees, demand charges, GST or sales tax and any amount carried over from a previous period.
- Does standby power really matter?
- A little. A device drawing 3 watts continuously uses about 26 kilowatt-hours a year, which is a few dollars. Across a dozen devices it becomes noticeable but never rivals heating, cooling or hot water. Switching off a set-top box and a games console at the wall is worthwhile housekeeping rather than a serious saving strategy.
- Can I use this outside Australia?
- Yes. The physics is identical everywhere, so only the rate changes. Enter your local price per kilowatt-hour in the currency you are billed in and read every dollar figure as that currency. United States residential prices commonly fall between 15 and 25 cents, and Great Britain between 22 and 28 pence, but always copy the number from your own bill.
Use this with
Power Bill Calculator answers one part of the question. These pick up where it stops: Solar Panel Savings Calculator, Energy Calculator, EV vs Petrol Cost Calculator, Electrical Load Calculator and HVAC BTU Calculator.
Where these figures come from
Figures and rules on this page follow Australian law and ATO guidance.
- Australian Energy Regulator. Default Market Offer and regulated electricity pricing in Australia
- Energy Made Easy (Australian Government). Official plan comparison showing usage rates and daily supply charges
- U.S. Energy Information Administration: Electricity. Published average residential electricity prices by state
- Ofgem: Energy price cap. Capped unit rate and standing charge for Great Britain
Power Bill Calculator produces an estimate for general information. It is not financial, tax, medical, legal or engineering advice. read the full disclaimer. Spotted a wrong number? Report it and it gets fixed. The form picks up this calculator and the inputs you used.