What each appliance really costs per day, month and year
Electricity bills are made of small multiplications nobody does: watts times hours, divided by a thousand, times the tariff. This calculator does them per appliance, with the duty cycle that separates a fridge (plugged in all day, compressor running perhaps 40 percent of it) from a heater (full power whenever it is on), and it applies the tariff structure you actually face: a flat rate, a tiered rate where the price steps up past a monthly allowance, or time-of-use rates where when matters as much as how much. Fixed monthly charges are added separately and labelled, because they are not energy and hiding them inside the per-kWh figure is how estimates quietly go wrong.
| Appliance | Watts | Hours per day | Duty cycle % | Qty |
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Disclaimer: This calculator gives estimates for general information only. It is not financial, medical or other professional advice. Tariffs, taxes and levies vary by supplier and region and change over time; your bill’s own rates are the figures of record.
What this calculator does
For each appliance it computes daily energy as watts x hours x duty cycle x quantity / 1,000, in kilowatt-hours, then prices that energy under the tariff you selected and reports cost per day, per month (a twelfth of a 365-day year) and per year, per appliance and in total, with any fixed monthly charge added to the month and year lines and named there. The point of the per-appliance table is diagnostic: a household bill is usually one or two appliances wearing a trench coat, and the table shows which ones, in currency, at your own tariff.
How to use it
- Watts from the label, hours from your life. Nameplate watts are on every appliance; hours are the honest guess most people skip. A plug-in energy meter settles both for a few dollars and turns this calculator from estimate to measurement.
- Duty cycle is the fridge correction. Anything with a thermostat or compressor cycles: fridges commonly 30 to 50 percent, air conditioners varying with the day, water heaters by draw. Set 100 percent for resistive loads that run flat out while on (heaters, kettles, ovens, lights).
- Copy your tariff from your bill, not from a headline. The per-kWh rate, the tier limit and the fixed charge are all printed on the bill or the supplier’s tariff sheet; teaser averages from comparison sites describe nobody’s actual meter.
- Time of use rewards timing, and the peak share is the dial. If your heavy loads (laundry, dishwasher, EV charging) can move off-peak, lower the peak share and watch the month figure: that difference is the entire value of the tariff type, priced.
How it is calculated
- Energy: kWh per day = watts x hours per day x (duty cycle / 100) x quantity / 1,000. Month = day x 365 / 12; year = day x 365.
- Flat: cost = kWh x rate. Tiered: the first (tier limit) kWh of the month at rate one, the rest at rate two, computed on monthly energy. Time of use: cost = kWh x (peak share x peak rate + off-peak share x off-peak rate). Fixed charges add to month and year only.
Worked examples
Flat rate, two appliances. Fridge 150 W x 24 h x 40 percent duty = 1.44 kWh/day; heater 2,000 W x 4 h x 100 percent = 8.00 kWh/day; total 9.44 kWh/day. At 0.17 per kWh: 1.60 per day, 287.13 kWh and 48.81 per month, 3,445.60 kWh and 585.75 per year. The heater is 85 percent of the story from a fifth of the fridge’s hours, which is the kind of fact that reorganises a household’s winter.
The same load on time of use. 30 percent of use at a 0.32 peak rate, 70 percent at 0.12 off-peak: the blended rate is 0.18, the day costs 1.70. Higher than the flat example here, deliberately: time-of-use only pays when the peak share is genuinely low or the flat alternative is higher, and the calculator’s job is to show your numbers, not to sell a tariff.
A fixed charge changes the month, not the physics. Add a 12.50 fixed charge to the flat example and the month becomes 48.81 + 12.50 = 61.31 while the energy is untouched: the reason two households with identical usage pay different bills, and the reason this page keeps the charge visible and separate.
Reading your results
Sort your eye down the per-appliance year column: that ranking is your savings plan in order, since a watt saved on the top row is worth its hours (the fridge’s 8,760-hour year makes small watt differences large). Then read the total against your actual bill; a persistent gap means an unlisted load (the second fridge in the garage is the classic) or standby draws the table does not model, and the limitations name that boundary. Finally, if you are choosing between tariffs, run the same appliances through each structure: identical energy, three prices, one honest comparison.
Limitations
- Duty cycles are estimates. A fridge’s cycle swings with room temperature, door openings and fill; the calculator prices the duty you enter, and a meter reading over a week replaces the estimate with a fact when the appliance matters.
- Standby power is not modelled per row. Devices drawing 1 to 10 W around the clock add up across a house (the so-called vampire load can reach several percent of a bill); add a row for a measured whole-house standby figure if you have one.
- Tariffs have more furniture than three models. Demand charges, seasonal rates, weekend structures, taxes and renewable levies exist beyond the flat, tiered and two-rate time-of-use forms here; where your tariff has them, add their monthly effect to the fixed charge line as an approximation and know it is one.
- Watts on labels are maxima for some devices. Variable-speed and inverter appliances modulate; a microwave’s food-heating watts differ from its electrical draw. Nameplate electrical input is the right input; cooking power is not.
Frequently asked questions
How do I work out what one appliance costs to run?
Multiply its watts by the hours it runs, divide by 1,000 for kilowatt-hours, multiply by your rate: a 2,000 W heater for 4 hours is 8 kWh, which at 0.17 is 1.36 a day, and the duty-cycle correction applies when the device cycles rather than running flat out (the fridge in the example uses 1.44 kWh from a nameplate that naive maths would price at 3.6). This page exists because doing that by hand for six appliances and three tariff shapes is where households give up; the arithmetic itself is exactly this paragraph.
Why is my bill higher than the calculator says?
Work the suspects in order: unlisted loads (second fridges, aquarium heaters, dehumidifiers, servers, outdoor anything), duty cycles set optimistically, standby draw across dozens of devices, fixed charges and taxes not yet entered, and a tariff that changed since the last bill you read. The calculator prices what you list at the rates you give; the gap between its total and the bill is a measurement of what is missing from the list, which is itself the most useful number on the page when it appears.
What is a kilowatt-hour, in plain terms?
It is one kilowatt of power sustained for one hour: the unit your meter counts and your tariff prices. A 100 W bulb for 10 hours, a 1,000 W heater for 1 hour and a 2,000 W kettle for half an hour are each exactly 1 kWh, which is why big-watt short bursts (kettles, toasters) cost less than their plates suggest and small-watt permanent loads (pumps, fridges, standby) cost more. Every figure on this page is that identity, priced.
Does turning things off at the wall actually save money?
For devices with real standby draw, yes, in proportion to their watts times 8,760 hours: a 5 W idle draw is 43.8 kWh a year, around 7.45 at the example rate, per device. The honest scale is per-device small, whole-house noticeable, and it is measurable rather than arguable: one row in this table with a metered standby figure settles any specific claim, which is the treatment this page gives every electricity question, including its own examples.
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Method: energy as watts times hours times duty cycle over 1,000; cost under flat, tiered or two-rate time-of-use tariffs with fixed charges kept separate. Last reviewed: 14 October 2026.