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.
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
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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.
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
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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