What Is A Kilowatt-Hour? A Guide to Understanding Your Electric Bill
Here’s what we’ll cover in this guide:
- What a kilowatt-hour is and how it differs from a kilowatt
- How to calculate how many kilowatt-hours appliances use
- How much a kilowatt-hour can cost
- Understanding your electricity bill
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Jump To: What Is a Kilowatt-Hour? | Kilowatt-Hour vs. Kilowatt | What Can One Kilowatt-Hour Power? | How Do I Calculate How Many kWh an Appliance Uses? | What Does One kWh of Electricity Cost? | How Many kWh Does a House Use Per Day? | What Determines Electricity Cost per kWh on an Energy Bill? | How to Find Your Electricity Usage | Can I Use kWh to Compare Energy Costs?
What is a Kilowatt-Hour?
A kilowatt-hour (kWh) is a way to measure electrical energy. It is most commonly used to measure how much energy a home or appliance consumes over a given period of time, and is equal to one kilowatt (kW) of power sustained for one hour.
Let’s do the math. First we need to differentiate between a watt and a kilowatt. One kW is equal to 1,000 watts, so a 1,000-watt appliance would use a kWh in one hour. A 100-watt light bulb would take 10 hours to use one kWh, while a 2,000-watt oven would use one kilowatt-hour in just 30 minutes.
Similarly, your monthly electricity bill is measured in kWh and measures the amount of electrical energy that your home consumes over the month. A typical household uses between 800 kWh and 1,200 kWh per month.
Check out this helpful explanation from Enphase Energy to learn more.
Kilowatt-Hour vs. Kilowatt
We’ve clarified that kilowatt-hours measure a unit of energy. A kilowatt (kW), on the other hand, is a unit of power. Power in this context refers to the rate at which something can produce, transfer or consume electricity.
We like to think about it this way: A kilowatt would refer to the horsepower or potential speed of a car, while kWh would refer to the actual distance the car has driven over a period of time.
When speaking about solar panel systems, the number of kilowatts refers to the maximum amount of energy the system can produce at any given time. For example, you might see a solar panel system described as a 10 kW system.
If you have a 10 kW system, it can theoretically produce 10 kW of power continuously. Your home could then draw from that energy source, providing the kWh that your home consumes over the day.
What Can One Kilowatt-Hour Power?
Here are some common examples of appliances that might use one kWh. The exact power levels will vary based on the efficiency of each product. The more efficient the appliance, the less energy it will consume.
- 100-watt light bulb for 10 hours
- Energy-efficient 40-watt light bulb for 25 hours
- 50-watt alarm clock for 20 hours
- 2,000-watt dishwasher for 30 minutes
- 200 to 400-watt fridge/freezer for around 3 hours
- 80-watt LED TV for 12.5 hours
- 10-watt router for 5 days
- 1,450-watt air fryer for around 40 minutes
How Do I Calculate How Many kWh an Appliance Uses?
While your home’s air conditioner or heating system will use the most electricity (close to 50% of the bill) throughout the month, your electrical appliances are a huge factor in the cost breakdown of your total energy usage. Dryers, refrigerators, water heaters and dishwashers are often the biggest culprits.
Many major appliances will have a tag or EnergyGuide label that lists the appliance’s model number, voltage, the location where it was made and the range of watts it can consume. Once you collect the wattage of your daily appliances, it’s fairly easy to calculate the electricity consumption of your home on a daily, monthly or yearly basis. Here is an example:
|Watts||Hours Used Per Day||Watt-Hours Per Day|
If your dishwasher is a 1,200-watt device and it runs for two hours every day, it uses a total of 2,400 watt-hours a day. (watts x hours used per day = watt-hours)
|Watt-Hours Per Day||kWh Per Day||kWh Per Month|
Once watt-hours per day are calculated, divide the number by 1,000 to find how many kWh of energy are used per day. You can then multiply that number by 30 or 365 to find its monthly or yearly consumption. (Watt-hours / 1,000 = kWh per day) x 30 = kWh per month
Online resources and calculators can help expedite the process. A spreadsheet could also be helpful, using the above calculations.
It is important to remember that some appliances still use energy in standby mode. This means if an electronic like a TV or laptop is left on standby, it is still consuming (albeit a small amount) power and adding kWh to the monthly electricity bill.
If you’re due to replace an appliance soon, investing in an energy-saving appliance can generate large savings over time.
How Many kWh Does a House Use Per Day?
The average U.S. home consumed 887 kWh of electricity per month in 2020.1 This breaks down to around 30 kWh per day.
How many kWh your household uses will depend on many factors, including:
- Size and age of your home
- Type, number and age of your appliances
- Your area’s climate
- How you heat or cool your home
- How many people live in the residence
- How much time you spend at home
A single occupant working full-time in an efficient home could consume as little as 6,000 kWh per year. On the other end of the spectrum, four college students sharing an old four-bedroom house could use roughly 12,000 kWh per year.
What Does a kWh of Electricity Cost?
The national average rate for electricity is around 13 cents per kWh but varies depending on where you live. If you happen to live in a deregulated market, the cost can depend on your retail electricity provider. The U.S. Energy Information Administration (EIA) reports on average prices by state.2
For our examples, we will use the national average rate.
If electricity costs 13 cents per kWh, then a 100-watt light bulb (0.1 kWh) will cost you $0.013 for every hour it is on (cost per kWh x energy use in kWh = hourly cost).
|Convert to kW||Cost Per kWh||Total Hourly Cost|
|100-watt light bulb||0.1||$0.13||$0.013|
Of course, electricity bills come monthly and not by the hour, so there are still a few calculations needed to estimate monthly costs.
- Multiply your total hourly cost by the hours per day the light bulb is used. For this example, let’s say it’s 3 hours.
$0.013 x 3 hours = $0.039 per day
- Multiply by 30 to calculate the monthly average of the appliance
$0.039 x 30 days = $1.17 per month
- Repeat this for all appliances and light bulbs in your home
- Add up the total to calculate the estimated monthly electricity costs in kWh
The EnergyGuide label on newer appliances includes its estimated yearly electricity usage. You can multiply that number by your rate per kilowatt-hour and find the cost to use that device.
What Determines Electricity Cost Per kWh on an Energy Bill?
As we’ve already discussed, the average cost per kWh in the U.S. is 13 cents, and the average household consumes 887 kWh per month. This means the average electricity bill is around $115, without any additional fees or charges from an electric company.
When it comes to your monthly bill, your kWh rates could depend on all of the following:
- Your electricity provider
- The terms of your contract
- The electricity prices in your state
- The amount of power you consume on average
- If your electricity comes from a renewable energy power plant
How to Find Your Electricity Usage
The easiest way to see how much electricity you use is to simply check your electricity bill. Your bill will show how many kilowatt-hours you’ve used in your home each month. Your electricity provider should also offer online tools to monitor your usage. Some companies have even started to add small bar charts to the monthly bill to visually show monthly trends and patterns.
If you have a Smart Meter, your electricity provider probably also provides online tools for you to track your power consumption. Some can send out weekly status reports to your email and forecast how much you might use in the upcoming week.
Here’s an example of where you might find your monthly electricity usage.
Can I Use kWh to Compare Energy Costs?
Yes, if you live in an area with deregulated electricity, you can use your estimated or billed monthly kWh to compare energy costs. This is where understanding the number of kWh that you consume per month comes in handy. Simply multiply the kWh you typically use by the electricity rate from the provider you’re considering to get an idea of what your monthly bill would be.
However, be on the lookout for any other fees that might not be reflected in the rate plan. This might include signup fees, early termination fees or plans that switch from fixed rate to variable rate automatically.
If you use an energy cost comparison tool, you can accurately calculate your total potential savings by entering energy use by kWh.