Appliance Wattage Calculator

A tool to calculate the power consumption of household appliances converts the power draw of a device into the actual numbers that matter on your electricity bill: kilowatt hours (kWh) used and the associated cost. You can either enter the wattage listed on the label directly, calculate it from voltage and current, or start with common household appliances and adjust them. The tool then converts the power consumption to daily, monthly, and yearly costs.

What does watt mean in household appliances?

Watt is a measure of the power consumption of an appliance and is measured in watts (W). A kilowatt (kW) equates to an appliance with a power rating of one kW running for one hour, which means it will consume one kilowatt-hour (kWh) of energy. This is the unit used by electricity suppliers to bill you.

The wattage alone does not give any information about the cost. A hair dryer with 1,500 W that is used only for five minutes has hardly any effect on the bill, while a refrigerator with 150 W that runs all year round can be one of the highest items in the electricity bill. The costs depend both on the wattage and on the operating time of the device.

Here's how to use this calculator:

First tell the tool how you determined the power usage. If there is a wattage listed on the label, enter it directly. If only voltage and current are listed, switch to the voltage and current mode, where the tool will automatically multiply both values together. For an estimate, select a common household item which will load the default wattage.

Firstly, you set how many hours per day and days per week a device is used for and input the cost of electricity based on your current energy bill. The values shown for power in watts, energy consumption and costs are updated in real time based on your inputs. Two optional toggles let you further refine the estimate: one to adjust the duty cycle of appliances that turn on and off repeatedly and another to calculate carbon emissions.

The calculation formula behind the numbers:

To calculate power from voltage and current, the tool uses this basic formula:

P is the power in watts, V is the voltage in volts, I is the current in amps and PF is the power factor. For simple resistive loads like heaters, kettles or light bulbs the power factor is 1. Motors and some electronic devices have a power factor less than 1 so the actual power consumed is slightly lower than the result of multiplying voltage by current.

The energy is the product of power and time, divided by 1,000 to convert from watt-hours to kilowatt-hours.

The costs are determined by multiplying energy consumption and electricity price per kWh.

A 1,500 watt heater is used for 4 hours each day and all seven days of the week. The cost of electricity is $0.17 per kilowatt hour. The daily energy consumption is 6 kWh (calculated as (1,500*4) / 1,000). Over a year this results in a consumption of 2,184 kWh (6*7 x 52) which at this electricity price would cost about $371.

Duty cycle - why a fridge doesn't run all the time

Some appliances like heaters or lamps run at full power as long as they are switched on. Other appliances work in a cycle. The compressor of a refrigerator starts and stops to cool then starts again. So it may use electricity only 40% to 80% of the time during the day. A duty-cycle switch can adjust the rated power according to this percentage, which allows more realistic estimates for refrigerators, freezers, air conditioners and thermostat-controlled heaters.

Standard Wattage for Common Household Appliances

These are the average wattages for running common household appliances. The actual values may vary depending on the brand, size, age, and settings of the appliance. Use these numbers as a starting point and check the label or use an electricity meter to determine the actual consumption if necessary.

The appliances that use the most electricity in your home

The biggest costs come from appliances that generate heat or run for long periods of time. Water heaters, furnaces, air conditioners and clothes dryers combine high wattage with long or frequent use. Routers and set-top boxes like electronic devices that are constantly running may not consume much power individually, but the sum can be substantial.

How to cut down on running costs of household appliances:

Calculate your consumption and start with the areas where the numbers are highest. Reducing the running time of high-wattage appliances will result in the greatest savings. Hanging laundry or reducing heating times is more effective than worrying about the power usage of a smartphone charger. Replacing old appliances with highly efficient models allows you to do the same work at lower wattages. Shifting your usage times to when electricity rates are cheaper does not reduce actual energy consumption, but it reduces the price per kilowatt hour.

The results provided by this calculator are for planning and comparison purposes only. Actual consumption will depend on the specific appliances used, settings selected, and local electricity rates. Local electricity rates may include tiered rates, time-of-use rates or flat rates that are not factored into this calculator.