Kilowatts and Calculations: What You Need To Know?

Kilowatts and Calculations: What You Need To Know?

by | Educational, Energy Resources, Energy Topics

Even if the subject of kilowatts isn’t something you think about every day, it’s certainly something that affects your daily life. You see, a watt is the basic unit of measurement used for electrical power. The term “watt” comes from James Watt of Scotland, an engineer, entrepreneur, craftsman, instrument maker, and scientist who is often referred to as the father of the Industrial Revolution. One of his most notable accomplishments was around 1775, when he invented the Watt steam engine. Today, steam turbines at thermal power plants use this same technology to convert thermal energy into mechanical energy. We measure that electrical power in kilowatts.  

In this guide, we take the complicated subject of kilowatts and simplify it into more relatable terms. Here, you’ll gain a better understanding of what kilowatts are, plus we’ll cover things like what we measure in kilowatts, how we convert and calculate kilowatts, and how kilowatts differ from kilowatt-hours, megawatts, and gigawatts. 

What Is a Watt?
What Is a Kilowatt?
 

Kilowatt Measurement Illustrationsource

Before we discuss kilowatts, let’s take a second to talk about watts (W). Watts are the basic unit of power used to measure electric, thermal, and mechanical power. One watt is equal to one joule, as well as one volt-ampere. All of these terms measure electrical power.   

Now, let’s get into a more detailed description of what a kilowatt (kW) is. Most simply, a kilowatt is another term used in the measure of power. Most frequently, we use kilowatts to measure residential and commercial power.   

Keep in mind that the prefix “kilo” means one thousand. It may be easier for you to remember that one kilowatt equals 1,000 watts of electrical power when thinking of the prefix’s meaning. For example, a microwave with a 1,000-watt label requires 1,000 watts worth of power (or 1 kW) to work.  

How Do You Convert Watts Into Kilowatts?
How Do You Convert Kilowatts to Watts? 
 

The conversion of watts to kilowatts is just as straight-forward as you may have guessed. We find the power in kilowatts P(kW) by dividing the power in watts P(W) by 1,000. 

Here’s the Formula for Converting Watts Into Kilowatts: 

  • P(kW) = P(W) / 1,000 

For example, if you wanted to convert your 1500W dishwasher to kilowatts, you would do the following calculation:  

  • P(kW) = 1,500W / 1,000 = 1.5kW 

Here’s another way to think of it that may make the math easier. Add a decimal point at the end of your whole number. In this case, it’s 1500. Then, since there are three zeros in 1,000, which is the number you’re dividing by, you will move the decimal point three digits, or three spaces, to the left. You end up with 1.500, or 1.5. This trick makes it really easy to convert watts into kilowatts with some quick mental math. 

Here’s the Formula for Converting Kilowatts Into Watts: 

Since we know that one kilowatt is equivalent to 1000 watts, we reverse the operations above to solve this equation.  

  • 1kW = 1000W 
  • P(W) = 1000 × P(kW) 

For example, if you know that your dishwasher uses 1.5kW, you would perform the equation below to find that your dishwasher is a 1500W appliance or requires 1500W of power to work.  

  • Convert 1.5kW to watts: 

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How Many Kilowatts Are in a Megawatt?   

Kilowatts in Megawatt Power | Electric photosource

We use megawatts when measuring power on a much larger scale. If you wanted to know how much power is produced by a power plant or how much electricity is required to power an entire city, you would use megawatts. For example, a typical coal power plant is around 600 MW in size.  

To continue along the path of keeping things simple, use the same formula used above to convert kilowatts to megawatts (MW). Why is that? Well, because 1,000 kilowatts are equal to you guessed it one megawatt. 

Here’s the Formula to Convert Kilowatts to Megawatts: 

This formula also means that if you would like to convert watts to megawatts, you have to add three more zeros to your equation. The power in megawatts P(MW) can be found by dividing the power in watts P(W) by 1,000,000. 

Here’s the Formula to Convert Watts to Megawatts: 

For example, if you convert a 100-watt light bulb to megawatts, you will do the following calculation:  

  • P(MW) = 100W / 1,000,000 = 0.000100MW 

How Many Megawatts Are in a Gigawatt? 

Suppose you’re looking for an even larger measurement unit. In that case, you’ll want to use gigawatts, which we use to measure how much power large power plants or several plants can generate together. In 2012, the total capacity of United States electricity generating plants was about 1,100 GW.  

You’ve likely noticed a pattern forming here. In that case, you may have a good idea as to what the formula is for converting megawatts to gigawatts (GW). If you guessed that there are 1,000 megawatts in one gigawatt, you would be correct. That fun fact means that there are 1,000,000 kilowatts in one gigawatt and 1,000,000,000 watts in one gigawatt. Whew! 

What Are Kilowatt-Hours?
Are Kilowatt-Hours Different Than Kilowatts?
 

Kilowatt-Hours Power and Energy | man with ipadsource

 Now, here’s where things can get a bit confusing. A kilowatt-hour (kWh) is a measurement of how much energy is used. However, this is not actually the same as measuring the number of kilowatts you use per hour because power and energy are not the same. Instead, a kilowatt-hour measures the amount of time, or the amount of energy, it takes to use one kilowatt of power.   

The amount of energy used if a 1,000-watt appliance runs for one hour is equal to one kilowatt-hour. The lower the wattage an item has, the better.   

Here’s an example: If you were to use a 100-watt light bulb, it would wield one kilowatt-hour of energy after 10 hours of use. But, if you switched to a more energy-efficient light bulb that only requires 40-watts to produce the same amount of light, it will take 25 hours to use one kWh of energy. Imagine the energy savings you could achieve by switching out all of the lightbulbs in your home.  

Just like measuring power consumption, when you calculate the amount of energy used or produced on a larger scale, you would use megawatt-hours (MWh) or gigawatt-hours (GWh).  

How Do I Calculate the Energy Consumption of an Electrical Appliance? 

How Is My Energy Use in Kilowatt-Hours Calculated?

Much like one kilowatt is equal to 1,000-watts of power, one kilowatt-hour is equivalent to 1,000-watts, or joules, of energy use over one hour. If you wanted to convert watts into kilowatt-hours to find out how much energy your coffee maker consumes each day, you would multiply the power consumption in watts by the number of hours used. Then, divide that number by 1,000. 

Here’s the Formula for Calculating Watts Into Kilowatt-Hours: 

  • kWh = (watts × hrs) ÷ 1,000 

For example, to find the kWh of 1,200 watts for 3 hours:  

  • kWh = (1,200 × 3) ÷ 1,000 
  • kWh = 3,600 ÷ 1,000 
  • kWh = 3.6 

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How Do I Convert My Energy Consumption of Kilowatt-Hours Into Watts? 

Suppose you were interested in doing the reverse to determine how many watts your coffee maker is, based on its kilowatt-hours. In that case, you could easily do so by making a few simple adjustments to the formula.  

For this conversion, multiply the energy used in kWh by 1,000 to find the energy consumption in watt-hours. Then, you must divide that number by the number of hours you used it. 

Here’s the Formula for Calculating Kilowatt-Hours Into Watts: 

  • watts = (kWh × 1,000) ÷ hrs 

For example: let’s find the watts of power for 3.6 kWh of energy used in 3 hours.  

  • watts = (3.6 kWh × 1,000) ÷ 3 hrs 
  • watts = 3,600 ÷ 3 hrs 
  • watts = 1200 W  

What Does One Kilowatt-Hour of Electrical Energy Cost? 

Kilowatt-Hour of Electrical Energy Costs illustration source

Most utility companies calculate your electricity bill based on how many kilowatt-hours, or units of energy you use each month. Since the scientific unit of energy is measured in joules, you will often see your energy usage listed in joules on your electric bill. Remember, one joule is equal to one watt. If you can convert watts to kWh, you can predict how much it might cost to run your various electrical appliances and devices. 

Using the latest electricity prices reported by the U.S. Energy Information Administration, a Choose Energy® Rate Report was compiled. The report shows how much energy costs vary depending on your location.   

In 2020, Idaho residents paid the lowest average electricity rates in the U.S. at 9.67 cents per kWh. In extreme contrast, residents in Hawaii paid the most, with their average 2020 electricity rates coming in around 28.84 cents per kWh. 

How Do I Calculate the Consumption of an Electrical Appliance?
How Do I Estimate What My Electricity Bill Will Be?
 

Let’s use the national average rate of around 13 cents per kWh to calculate how much it costs to power a 100-watt light bulb every hour. Since it takes 100 watts of power to work to convert the power in watts to kilowatt-hours you will multiply 100 watts by one hour. Then, you’ll divide by 1,000 to find the energy usage in kWh.  

  • Energy = (100 × 1) ÷ 1,000 
  • Energy = 100 ÷ 1,000 
  • Energy = 0.1 kWh 
  • Hourly cost = electricity cost per kWh ÷ energy use in kWh 
  • Hourly cost = $0.13 ÷ 0.1 kWh 
  • Hourly cost = 1.3 cents 

If electricity costs 13 cents per kWh, then a 100-watt light bulb will cost 1.3 cents for every hour that it’s on. Most electric bills are calculated monthly. To estimate your monthly costs, you can follow these steps:  

  1. Estimate how many hours per day you use that light bulb on average. (Let’s say it’s 5 hours).

  2. Multiply the light bulb’s watts by the average number of hours you use it daily instead of the one hour used in the formula above. (Let’s say your light bulb is 60 watts, so that you would calculate 60 watts x 5 hours).

  3. Solve the equation above using your light bulb’s actual wattage and the actual average number of hours you use that light bulb per day. (60 x 5 = 300 ÷ 1,000 = 0.3 kWh). 

  4. Divide your area’s average electricity cost by your light bulb’s average daily kWh. ($0.13 ÷ 0.3 kWh = 43 cents per day.  
     
  5. Multiply your answer by 30 to get the monthly average kWh for that light bulb. In this case, $0.43 x 30 days = $3.90. It would cost you $3.90 per month to leave a 60-watt light bulb on for an average of 5 hours per day, every day. 
     
  6. Repeat this equation for all light bulbs, appliances, and other electrical devices in your home.  
     
  7. Add up the total to find your estimated monthly electricity costs in kilowatt-hours. You may be surprised to see how fast it all adds up. 

How Many Kilowatt-Hours Does the Average U.S. Household Use Per Day? 

Kilowatt-Hours Use | United States | Average Meter photosource

Now that you know all about how to calculate the kWh of energy consumption you use, it might be interesting to compare your energy use to others in the United States. The average home in the U.S. consumed 887 kilowatt-hours (kWh) of electricity per month in 2019, which breaks down to almost 30 kWh per day. If you’re curious to see where you stand compared to others in your specific region or state, check out this data provided by the U.S. energy information administration. 

How Many Kilowatts Should a Generator Be to Run a House? 

If you live in an area prone to weather that could result in power outages, you can give yourself a little peace of mind by investing in a generator. Freezers, lights, refrigerators, and well pumps are just a few of the appliances you could keep running during a power outage.   

The most critical household equipment can be run with a 5,000 to 7,500 watt rated generator. If you would like your entire house to continue operating, you will likely need to go larger. If you have fewer appliances, you may be able to get away with something smaller. Determining the wattage of your necessary appliances will help you figure out what size generator you will need. 

What’s the Difference Between Watts and Amps? 

Watts and amperes, also known as amps, are both units used to measure electrical power consumption or production. All electronic devices have their energy consumption listed on their label in either watts or amps. If the label on your device lists amps, you can calculate the wattage by using a simple formula. 

Here’s the Formula for Calculating Amps to Watts: 

Wattage = Amps x 120  

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For example, if you have a 120V device with a 20 amp label, that’s equivalent to a wattage of 2400. In equation form, that is: 20A x 120V = 2400W 

What Is the Kilowatt-Peak?  

Kilowatt-Peak kwp | Solar energy on roof imagesource

Kilowatt-peak (kWp) refers to the rate a system can generate energy during its peak performance, which is when it’s working at its maximum capacity. We most commonly use kWp for solar electricity systems. These systems are labeled with a rating in kilowatts peak (kWp) so that consumers can compare the output capabilities and size of various photovoltaic panels  

A 2 kWp system will produce 2 kW of electrical power only during the brightest sunshine when all conditions are at their best. Standard modules take around 6.25 square meters of roof space for each kWp. Higher efficiency modules use only five square meters of roof space. 

How Technology Is Changing the Energy Industry 

There’s no question that technology has improved by leaps and bounds over the years. Things aren’t any different in the energy industry. Let’s take a look at two excellent examples. 

How Much Does It Cost to Charge a Tesla? 

Tesla has been around since 2003, but now that electric cars are becoming more common, they’re also becoming more affordable. As gas prices are going up, the cost to charge electric vehicles is going down. Take a look at this example which explains how much it costs to charge a Tesla Model 3 at a home charging station:  

  • The battery capacity is 75kW, and our current average electricity rate that we’re going to use is 13 cents per kWh 
  • This means that your charging cost is equal to 75 x $0.13 = $9.75 for a complete “fill up” that will get you around for approximately 240 miles. 
  • Compare charging the Tesla to filling up a smaller car that has a 12-gallon gas tank. When we use a gasoline cost of $3.85 per gallon, it’s pretty clear that the $46.20 you spend on filling up your car with gas (12 x $3.85 = $46.20) is way more expensive than using the Tesla charging station. It may get you 300-400 miles of drive time, but even charging the Tesla twice is less than half the cost of one tank of gas.  
  • Bonus: By driving an electric car, you’ll reduce your carbon dioxide emissions and become a part of the fight against climate change. 

Measuring Your Energy Use Is Simple With a Smart Meter 

Smart meters automatically send your daily and hourly energy usage data to your utility company’s central computer system. This technology provides real-time data allowing both parties an in-depth look into current usage habits, eliminating the need for meter readings.   

Smart meters allow consumers access to information on how, when, and where utilities are used, making it simple to make changes when necessary.  

Now You Know Kilowatts 

Kilowatts Learning | image of young girl holding piggy banksource

 Now that you know how to use your newfound knowledge of kilowatts to save energy, you may be interested in learning about more ways to save on your electric bills. Check out the Energy Savings marketplace where researching your energy options is easy, plus learn more about getting started on your path towards energy conservation today. 

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