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Appliance names, power, rates, notes and results stay on this page. Saving uses browser storage and can be deleted from the form.
Electricity usage calculator
Electricity Cost and Usage Calculator
Estimate appliance energy cost, compare devices, include standby power and test simple or peak and off-peak electricity rates. Calculations run locally in your browser.
- One appliance or a full multi-device simulation.
- Cost by hour, day, week, month and year.
- Scenario comparison without creating an account or sending your data.
Estimate electricity cost
How the electricity calculation works
The calculator converts watts to kilowatts, multiplies by usage time, applies quantity and optional running percentage, then multiplies kWh by the rate you enter.
Watts to kW
kW = W / 1,000A 1,000 W appliance is 1 kW. A 1.5 kW appliance used for four hours uses 6 kWh before optional factors.
Energy use
kWh = kW × hours × quantity × running factorThe running factor is 100% unless you explicitly change it for a cycling appliance.
Monthly convention
monthly kWh = daily kWh × 30.4375This uses 365 days divided by 12 months so day, month and year stay consistent.
Electricity cost
cost = kWh × electricity rateIn peak and off-peak mode, the matching kWh are multiplied by each rate.
Standby power
standby kWh = standby W / 1,000 × standby hoursStandby is shown separately so it is not hidden inside active use.
Scenario savings
savings = current cost - new costThe percentage is calculated against the current scenario and left blank when the current cost is zero.
Electricity cost guide
Power and consumption are different
Power in watts describes how fast an appliance can use energy. Consumption in kilowatt-hours depends on how long it runs.
Finding your kWh rate
Look for the energy price per kWh on your electricity bill. If your bill separates supply, delivery or taxes, add only the parts you want included.
Peak and off-peak rates
Use time-of-use mode when your bill has different prices. Enter how many daily use hours happen in each period.
Devices that run in cycles
Washers, dryers and dishwashers are often clearer with kWh per cycle. Use the cycle units and enter the value from the label or manual.
Standby power
Routers, consoles, chargers and TVs may keep drawing a small amount when idle. Add standby watts and standby hours if you want it included.
Emission estimates
CO₂ output is optional because factors vary by country, provider and time. Enter a factor only when you have one you want to use.
Examples
Simple appliance
1,000 W for 2 hours per day at 0.25 per kWh.
The daily use is 2 kWh and the estimated annual cost is 182.50.
Standby mode
5 W in standby for 20 hours per day.
Standby use is 0.1 kWh per day before multiplying by the rate.
Old versus new appliance
A 1,500 W appliance compared with a 900 W appliance at the same usage time.
The lower-power scenario reduces monthly and annual running cost when the rate and duration stay the same.
Important limits
- The result is not an official bill, meter reading or certified measurement.
- Preset powers are starting estimates and should be replaced with your appliance label when possible.
- No official tariff, tax, subscription or national CO₂ factor is assumed automatically.
Sources and verification
The formulas use general electricity units and user-provided rates. These references document the units, price variability, appliance-label limits and emissions-factor context.
- U.S. Energy Information Administration - Measuring electricity
Defines watts, kilowatts and kilowatt-hours used in the calculator formulas.
- U.S. Energy Information Administration - Electricity prices and factors
Explains why electricity prices vary, which is why the calculator asks for your own kWh rate.
- U.S. Federal Trade Commission - EnergyGuide labels
Explains that appliance energy-cost labels are estimates and depend on actual use and local energy prices.
- International Energy Agency - Emissions Factors
Documents electricity-related emissions factors by country and period; the calculator uses only the factor you enter.
Use the percentage calculator when you want to express energy savings as a percentage.
Electricity cost FAQ
How do I calculate the electricity use of an appliance?
Convert watts to kilowatts, multiply by the hours used and multiply by the number of appliances.
How do I convert watts to kWh?
Divide watts by 1,000 to get kW, then multiply by hours. For example, 1,000 W for 2 hours equals 2 kWh.
What is the difference between kW and kWh?
kW is power at a moment. kWh is energy used over time and is the unit usually billed by electricity suppliers.
How do I find the kWh price on my bill?
Look for the unit price, energy rate or price per kWh. Use the value that matches the costs you want to include.
How is monthly cost calculated?
Daily kWh is multiplied by 30.4375 days, then by your kWh rate. Weekly and yearly values use the same 365-day convention.
Why can real consumption be different?
Actual use depends on model, temperature, age, settings, duty cycle and whether the rated power is reached continuously.
How do I calculate a cycle-based appliance?
Choose a cycle unit and enter kWh per cycle from the appliance label or manual.
How do I calculate standby power?
Enter standby watts and standby hours per day. The calculator adds that kWh to the appliance total and shows the cost separately.
Can I compare several appliances?
Yes. Add appliances to see total cost, total kWh and the highest-consuming devices.
How do peak and off-peak rates work?
Enter both rates and split the daily usage hours between peak and off-peak periods.
Does the calculator use an official tariff?
No. Tariffs change by contract and location, so you enter the rate from your own bill.
Are my appliance data sent to a server?
No. The calculation runs locally in your browser. Saving uses local browser storage only.
Can I print or export the results?
Yes. You can copy a summary, export a CSV file or print the page to save a PDF.
Are taxes and fixed fees included?
Only if you add them explicitly. The basic calculation multiplies kWh by the rate you enter.
How can I reduce appliance running cost?
Reduce usage hours, lower standby time, choose efficient settings or compare a lower-power scenario.