The unit of energy equivalent to 3,600 joules is referred to as Watt-hour and symbolized as Wh. It equals power expended for one hour of time.
Kilowatt-hours are used for households due to more energy consumption by the appliances and tera-watthours is used for measuring even larger entities such as for any business enterprise or the whole country’s energy consumption.
Watt-hours are useful for measuring the energy of multiple devices such as a battery having a rating of 10-amp hours (Ah) functioning at 12 volts.
Multiplying the voltage with amp hour reflects the Wh of the battery which is mentioned as follows:
12 V x 10 Ah = 120 Wh
Watt Vs. Watt-Hour
The main difference that lies between watt and watt-hour is that the watt is a unit of power that measures the energy needed for an electrical device to operate by indicating the rate of electricity flow over one second.
On the other hand, a watt-hour is a unit of energy used for measuring the amount of work or energy consumed by an appliance or device over a certain period of time. It calculates the watts used within one hour.
Also See: What is Horsepower?
Watt-Hour Calculation
The first step to calculating the watt-hour is determining the watt of the device, the formula of which is mentioned below:
W = J/s
Next, for calculating the amount of energy consumption per device, the wattage rating is multiplied by the number of hours used per day.
Example:
An air conditioner has a wattage rating of 1,000 watts and the time period it is used for is 4 hours in one day then the watt-hour is:
Watt-hour (Wh) = watts x hours
= 1,000 x 4
= 4,000
Calculation: Appliance watts x hours used per day = daily watt hours consumption.
To calculate watt-hours when joules are given, multiply the number of joules by 2.778 x 10-4.
Converting Watt-Hour(Wh) to Watt(W)
In order to convert watt-hours to watts, the energy (E) in watt-hours is divided by the time period (t) in hours (h).
Example:
The energy consumption of a device is measured to be 40 watt-hours which is utilized for a total number of 5 hours in a day. The power consumption can be calculated as follows:
Watt = watt-hour/hours
Watt = 40/5 = 8
Must Read: What is Voltage Protection Rating (VPR)?
