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Energy and Power Consumption Calculator – kWh Calculator

How to Calculate Power and Energy Consumption in kWh? Calculator & Examples

Energy & Power Consumption Calculator in kWh

Enter electric appliance in the dropdown menu or enter manual wattage rating in watts or kilowatts (kW) and the daily usage of the device in hours. Click the calculate button to determine the daily, monthly and annual power usage or energy consumption in kWh.

Typical Appliance:
Power Usage:
Hours of Use per Day:Hours/Day
Energy Consumed per Day:kWh / Day
Energy Consumed per Month:kWh / Month
Energy Consumed per Year:kWh / Year

Calculation of Energy Consumption in kWh

Electric energy or power consumption can be calculated using the following basic formula.

Energy Consumption in Watt-hours = Power Rating in Wattage x Time in Hours 

E = P x t     …     Wh

“Wh” is a small unit to measure the energy usage. To convert it to the basic electricity unit i.e. 1000 Watts per hour = 1kWh = 1 Unit of electricity, we divide it by 1000 i.e.

E = P x t ÷ 1000     …     (kWh)


  • E = Electric Energy (Consumed power in kWh)
  • P = Power in Watts
  • t = Time in hours per day

Good to know:1 Unit of Electricity = 1 Board of Trade Unit = 1 B.O.T Unit = 1kWh = 1000Wh = 36 x105 … Joule or Watt-seconds = 3.6 MJ

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Energy and Power Consumption Calculator

Daily Energy Consumption

Power Consumption (Daily) = Power Usage (Watts) x Time (Hours)

Example: An 80 watts fan used for 4 hours daily. The daily watt hour and kilowatt hour consumption is as follows.

  • Daily power usage in Wh = 80W x 4 Hours = 320 Wh / day
  • Daily power usage in kWh = 320 Wh /1000 = 0.32 kWh / day

Monthly Energy Consumption

Power Consumption (Monthly) = Power Usage (Watts) x Time (Hours) x 30 (Days)

Example: A 25 watts LED light bulb operates for 8 hours on a daily basis. Find power consumption in Wh in kWh per month.

  • Monthly power usage in Wh = 25W x 8 Hours x 30 days= 6000 Wh / month
  • Monthly power usage in kWh = 6000 Wh /1000 = 6 kWh / day

Annual Energy Consumption

Power Consumption (Annual) = Power Usage (Watts) x Time (Hours) x 365 (Days)

Example: A 1700 Watts Electric kettle runs for 1 hours daily. Calculate the energy consumption in Wh and kWh in one year.

  • Annual power usage in Wh = 1700W x 1 Hours x 365 days= 620500 Wh / year
  • Annual power usage in kWh = 620500 Wh /1000 = 620.5 kWh / year

How to Calculate Power Consumption in kWh?

The following example shows how to calculate your electrical energy and power consumption “Wh” and “kWh” on a daily, monthly and annual basis. To do this, you must know the wattage rating of the device in watts (or voltage x current rating = power rating) and the operation time of the appliance in hours.


If an electric water heater of 2kW runs for 3 hours per day. Find the total daily, monthly and annual power consumption in kWh. (Take 30 days = 1 month, and 365 days = 1 year)


1. Daily Power Consumption

Daily Power Consumption = Wattage rating x time in hours

2000 Watts x 3 Hrs = 6000 Watts-Hour

Daily Power Consumption = 6 kWh

2. Monthly Power Consumption

Monthly Power Consumption = Wattage rating x time in hours

2000 Watts x 3 Hrs x 30 days = 180000 Watts-Hour

Monthly Power Consumption = 180 kWh

3. Annual Power Consumption

Annual Power Consumption = Wattage rating x time in hours x 365 days

2000 Watts x 3 Hrs x 365 days = 2190000 Watts-Hour

Daily Power Consumption = 2190 kWh

Power Consumption of Typical Home Appliances in Watts

The following table shows the estimated value of wattage rating (in Watts) for different and common household devices, appliances and equipment.

Electrical AppliancePower Wattage in Watts “W”
LED Light Bulb25
AC – Air Conditioner900
Electric Heater2000
Water Heater4000
Hair Dryer1500
Clothes Dryer3000
Clothes Iron1400
Electric Kettle1700
Toaster Oven1100
Microwave Oven1000
Desktop Computer150
Laptop Computer100
TV – Television120
Stereo Receiver300
Vacuum Cleaner1200
Washing Machine1500
Coffee Machine1000
Water Pump800
Sewing Machine100
Thankless Water Heater15000

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