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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 / month

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

Annual 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 Appliance Power Wattage in Watts “W”
Fan 80
LED Light Bulb 25
AC – Air Conditioner 900
Refrigerator 250
Electric Heater 2000
Water Heater 4000
Hair Dryer 1500
Clothes Dryer 3000
Clothes Iron 1400
Dishwasher 1300
Electric Kettle 1700
Toaster Oven 1100
Microwave Oven 1000
Desktop Computer 150
Laptop Computer 100
TV – Television 120
Stereo Receiver 300
Vacuum Cleaner 1200
Washing Machine 1500
Coffee Machine 1000
Blender 500
Water Pump 800
Sewing Machine 100
Thankless Water Heater 15000

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