Electricity Cost Calculator
Find out how much electricity your appliances use and what they cost per day, week, month and year, one at a time or a whole household together. Or estimate a bill from two meter readings, your price per kWh, fixed charges and taxes.
Runs in your browser. Your data is not uploaded.How our tools work
The rate per unit on your bill. No tariffs are built in.
Compare two appliances
For example an old fridge and a new one, or a regular and an inverter air conditioner, used for the same time. Enter a price per kWh above to see costs.
How do I calculate the running cost of an appliance?
Multiply the appliance’s power in watts by the hours it runs and divide by 1,000 to get kilowatt-hours (kWh), then multiply by your price per kWh. A 1,500 W heater used 4 hours a day uses 6 kWh, which at 0.20 per kWh costs 1.20 a day, 36.50 in an average month and 438.00 a year.
- In the Appliance calculator, enter your price per kWh from your bill, and pick a currency if you want one shown.
- For each appliance, pick a type to fill in a typical wattage or enter the power from its label, then the hours and minutes it runs a day, the days a week and how many you have.
- Add more appliances to see the household total, each one’s share and what stands out. Open Standby power for devices left plugged in.
- To check a bill, switch to the Bill estimator and enter the previous and current meter readings, fixed charges and any taxes.
Formulas & Methods
Energy from watts
Example: 1,500 W × 4 h × 1 ÷ 1,000 = 6 kWh a day
Energy from kilowatts
Example: 1.5 kW × 4 h × 1 = 6 kWh a day
Cost
Example: 6 × 0.20 = 1.20 a day
Week, year and month
Example: 6 × 7 = 42 kWh; 42 × 365 ÷ 7 = 2,190 kWh a year; ÷ 12 = 182.5 kWh, or 36.50, a month
Standby
Example: 1 W × (168 − 22.5) ÷ 1,000 = 0.1455 kWh a week
Bill
Example: 12,350 − 12,000 = 350 units; 350 × 45 + 150 = 15,900
Key features
A whole household
Up to 20 appliances, each with its own hours, days and quantity, with totals, shares and a breakdown.
Appliance presets
18 common appliances fill in a typical, rounded wattage. Real models vary, so change it to the figure on your label.
Day, week, month and year
Energy and cost for every period, with months as an average twelfth of a year.
Standby power
Counts what a device draws while plugged in but not running, for the rest of the week.
Bill estimator
Units from two meter readings, plus fixed charges and taxes as amounts or percentages.
Compare two appliances
What switching to a lower-power model saves a month and a year at your price.
Copy, share or print
Take the results as plain text, or print just the calculator and its results.
Common uses
- Find which appliances make up most of a household’s electricity use
- See what an air conditioner, heater or water heater costs to run each month
- Estimate the cost of gaming, charging or running a home server
What is a kilowatt-hour?
A kilowatt-hour (kWh) is the energy used by something drawing 1,000 watts for one hour. A 100 W bulb takes ten hours to use the same 1 kWh, and a 2,000 W kettle takes half an hour. Electricity bills charge by the kWh, and many call it a unit.
Watts and kilowatts measure how fast an appliance uses energy; kilowatt-hours measure how much it used over a time. That is why the calculator needs both the power and how long the appliance runs. 1 kW is 1,000 W, so 1,500 W and 1.5 kW are the same: enter whichever your label shows and choose the unit beside it.
Worked example: a household
Four appliances, every day unless stated, at 60 per kWh, for an average month:
- Air conditioner, 1,500 W for 8 hours a day: 12 kWh a day, 365 kWh a month, 21,900.00
- Refrigerator, 150 W around the clock: 109.5 kWh a month, 6,570.00
- Television, 100 W for 4 h 30 min on 5 days a week: 9.78 kWh a month, 586.61
- Five 10 W LED bulbs for 6 hours a day: 9.13 kWh a month, 547.50
- Total: 493.4 kWh, or 29,604.11, a month. The air conditioner is about 74% of it, and running it one hour less a day would save 45.63 kWh, or 2,737.50, a month.
How the monthly figure is worked out
Every period comes from the energy used in a week, so appliances used on different days add up correctly. A year is 365 days (the week × 365 ÷ 7) and a month is a twelfth of it: an average month of about 30.42 days, so twelve months make exactly the year. A 31-day billing period uses about 2% more than this, and February about 8% less.
The average day is the week divided by 7. For an appliance used only on some days, the energy on a day it is used is higher: a washing machine run 2 days a week uses its whole weekly energy on those 2 days.
How to estimate a bill from meter readings
Subtract the previous reading from the current one to get the units used, and multiply by the price per kWh for the energy charge. Then add fixed charges, such as a standing charge or meter rent, and any other lines on your bill. Each can be an amount, a percentage of the energy charge (some duties work this way) or a percentage of the subtotal: the energy charge, fixed charges and the amounts. Percentages are never charged on other percentages; if your bill does that, enter the tax as an amount.
Example: 350 units at 45 is an energy charge of 15,750.00. With fixed charges of 150, an electricity duty of 1.5% of the energy charge (236.25), a meter rent of 25 and a sales tax of 17% of the 15,925.00 subtotal (2,707.25), the estimated bill is 18,868.50.
Why your real bill may differ
The estimate is only as close as the figures entered. Common reasons for a gap:
- The label shows the maximum power. Fridges, air conditioners, heaters and irons switch on and off with a thermostat, so they draw full power only part of the time; a plug-in energy meter shows the real figure.
- Slab or tiered tariffs charge more per unit as use rises, and time-of-use tariffs change the price by the hour. For a slab tariff, use the energy charge on a recent bill divided by its units as your price.
- Fixed, minimum and fuel-adjustment charges, taxes and arrears, which the Appliance calculator leaves out (the Bill estimator adds what you enter).
- The billing period is not an average month, or a reading was estimated rather than read from the meter.
Frequently Asked Questions
How do I convert watts to kWh?
Multiply the watts by the hours used and divide by 1,000. A 60 W fan running 10 hours uses 60 × 10 ÷ 1,000 = 0.6 kWh. Watts are a rate of use; kWh are the amount used over time, which is what you pay for.
How much electricity does a 1,000 W appliance use?
1 kWh for every hour it runs at full power. Used 2 hours a day, that is 2 kWh a day, about 60.8 kWh in an average month and 730 kWh a year.
Can I add up several appliances?
Yes. Add up to 20 appliances, each with its own power, time, days a week and quantity, and the totals, shares and breakdown update as you type. Use the quantity for several identical ones, such as five bulbs.
Does the estimate include taxes and fixed charges?
Not in the Appliance calculator, which works out the energy cost only. The Bill estimator adds fixed charges and any taxes or surcharges you enter, as amounts or as percentages of the energy charge or the subtotal.
How do I use it with a slab or tiered tariff?
Enter an average price: the energy charge on a recent bill divided by the units on it. That stays close while your use stays in the same slabs, because the calculator applies one price to every unit.
How much does standby use?
Usually a few watts. A device left on standby at 2 W around the clock uses about 17.5 kWh a year: 2 × 24 × 365 ÷ 1,000.
Where do I find my appliance’s wattage?
On the rating label, often on the back or underneath, or in the manual. If it gives volts and amps instead, multiply them: 230 V × 2 A = 460 W.
Does VektraTool store my electricity usage?
No. The calculations run in your browser; the appliances, readings and prices you enter aren’t sent anywhere or saved, and reloading the page clears them. Analytics, if you allow them, record only that the calculator was used, never your figures.
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