Why do we measure electricity in kilowatt-hours (kWh)

In this article, we’ll explore everything we know about kilowatt hours, how we calculate them, and why we need to measure electricity in the first place.

If you’ve looked closely at your electricity bill, you’ve probably noticed that your service provider measures your energy in kilowatt-hours (kWh). In fact, this unit of measurement is used by nearly all household appliances, devices, and gadgets. But what exactly are kilowatt hours and why do we use them so often?

electricity bill

Why do we measure electricity in the first place

If you give any thought to this question, you may find the answer quite obvious. We need a standard unit of measure to understand how one device’s consumption compares to another. We also need a way to measure how much energy we generate.

For example, common sense tells us that a light bulb consumes far less energy than an air conditioner, but how much? How do we know we’ll have enough power to run both? That’s why there must be a consistent way of measuring electricity.

What does a kilowatt hour measure

In order to understand this, we must first understand watts. Watts tell you how much energy your device is using. In fact, you can find out how many watts a device uses by multiplying volts by amps. So it will tell you the rate of power flowing to the device.

On the other hand, one kilowatt is one watt multiplied by 1,000. Like kilograms and kilometers, kilowatts are simply units that are better suited for larger measurements.

So, now that we know about watts and kilowatts, what does a kilowatt-hour measure? Essentially, it tells us the total amount of energy used over time. For example, one kilowatt hour equals 1000 watts of electricity consumed in one hour. Therefore, different devices will consume different amounts of energy over time. For example, a light bulb might take 10 hours to consume a kilowatt-hour, while a microwave might take less than 15 minutes to consume a kilowatt-hour.

It is also possible to use kWh to calculate how much energy is produced. For example, a solar panel system producing 1000 watts for one hour will produce 1Kwh of energy.

kilowatt hour measure

KW vs kWh: What's the Difference

So what’s the real difference between kilowatts and kilowatt hours? The answer comes down to instantaneous power versus energy used over time. A kilowatt is just a name for 1,000 watts. The 1,000 watts can be consumed all at once or within four hours. We really don’t know because all we learn from it is the amount of energy, not the time.

A kilowatt hour tells us the number of kilowatts and how long it takes to consume them. Going back to our microwave oven and light bulb example, both consume one kilowatt, but how long do they each take? That’s what kWh tells us: the actual flow of energy in usable terms.

In descriptive terms, we refer to watts or kilowatts as “power” and kilowatt-hours as “energy.”

KW vs kWh

Why measure electricity in kilowatt hours

It’s actually not just measured in kilowatt-hours, but any derivative of watts. This could be watt hours (WH) or even megawatt hours (Mwh).

Electricity is measured in kilowatt-hours simply because it is easily convertible across all electricity usage ranges. If you need to measure energy on a small scale, you can use watt-hours; if you’re calculating large-scale energy use, you can use megawatts (1 kW x 1,000) hours.

Also, larger grids use this measurement to calculate how much energy each household uses, so everything from your appliances to your electricity bills measure electricity usage this way. Why? Because it’s just the best way to standardize the amount of energy we all use.

measure electricity in kilowatt hours

How do you calculate kilowatt hours

As mentioned earlier, one kilowatt consumed in one hour is equal to one kilowatt hour. So if you run a one kilowatt device for one hour, you will use one kilowatt hour. If you let it run for two hours, you’ll use 2 kWh, and so on. You need to know watts and time to calculate kilowatt hours.

Here are some examples.

1000w x 1Hr = 1kWh

1W x 1000Hr = 1kWh

1W x 1Hr = 1Whr or from 1kWh = 1/1000kWh .001Kwh

20w x 3Hr = 60Wh/1000kWh = .06kWh

400w x 24Hr = 9600Wh/1000kWh = 9.6kWh

kWh vs Amp Hour: What's the Difference

Remember the equation for determining watts? Volts x Amps = Watts.

In this case, volts are like water pressure flowing through a pipe, while amps represent volume. This then determines the flow rate (i.e. watts). How do we determine the flow of energy over time? You guessed it: kilowatt hours.

But without volts, you only have amps. So an amp hour is really just over an hour of charging current. We need volts to measure energy, so ampere hours are a measure of charge, usually reserved for battery sizing.

What is a wattage meter

The wattmeter is an instrument for measuring the electric active power (or the average of the rate of flow of electrical energy) in watts of any given circuit. Electromagnetic wattmeters are used for measurement of utility frequency and audio frequency power; other types are required for radio frequency measurements.

What are the three types of electrical measuring instrument

Classification of Electrical Measuring Instruments

· Absolute Instrument.

· Secondary Instrument.

· Indicating Instrument.

· Recording Instrument.

· Integrating Instrument.

· Null Deflection Instrument.

· AC Instrument.

· DC Instrument.


kWh is used to determine home energy usage, but the grid is measured in millions of watt-hours or megawatt-hours. Measure electricity is essential when making sure our appliances are working properly. This is where the kilowatt-hour comes in handy. They are a convenient way to determine how much energy we expend over time, and we use them in a wide variety of situations.

After all, each of our appliances consumes a certain amount of kilowatts when in operation. Without this measurement, we wouldn’t know how much power is required to run these electronics in the first place. When planning an off-grid solar or backup power system, it is necessary to know how much energy you are using to properly size the battery pack and system components.

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