Power & Energy Calculator – Precise kWh Estimation Tool

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.

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)

Where:

• 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

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.

Example:

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)

Solution:

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 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