Here you'll find a simple overview of kilowatt-hours (kWh), kilowatts and watts. We'll help you learn some basics about these terms and measurements. Plus, we'll help answer questions like how many kilowatts are needed to run a whole home generator or many watts solar panels can produce.

What is a kilowatt-hour?

Choosing an electricity plan that fits your needs can start with a basic understanding of how retail electricity usage is measured, along with knowing the power requirements of the appliances, devices and systems throughout your home. At the heart of this knowledge is familiarity with kWh (kilowatt-hours) and watts (not to mention kilowatts), and how these measurements relate to each other.

For starters, familiarizing yourself with the meaning of a kilowatt hour can help you monitor your electricity bill and adjust your electricity usage for greater efficiency. Once you better understand what a kWh is and how kWhs are translated to your power bill, you can perform some basic calculations that can help you approximate monthly usage and perhaps reveal ways to save.

For starters, what is a watt?

A watt is the base unit of power in the International System of Units (SI), named after engineer James Watt, whose work helped spark Britain’s industrial revolution. Technically, per the dictionary definition, a watt is equivalent to one joule per second, corresponding to the power in an electric circuit in which the potential difference is one volt and the current one ampere.

But in case you’re not an electrical engineer, in more basic terms, a watt quantifies the rate of energy transfer. Wattage measures how fast an appliance like a toaster or a fridge uses energy.

Kilowatt vs. kilowatt-hour: What’s the difference?

A kilowatt is equivalent to 1,000 watts and is a common measure of how much energy a device or appliance consumes.

• Dividing the number of watts by 1,000 results in the number of kilowatts.
• Conversely, multiplying kilowatts by 1,000 results in a number of watts.

Going a step further, kilowatt hour measures the energy something uses per hour. For example, if you used a 1,000-watt food processor for an hour, that’s 1 kWh of energy consumed. As you might expect, when you see kWh used on your electricity bill, that reflects the cumulative amount of electricity you’ve used over the course of your bill’s measurement period.

Kilowatt-hours (kWh) to watts conversion

You may be wondering how to convert the kilowatt-hours you see on your electricity bill to watts. The website Inch Calculator offers simple plug-and-play conversion tool. All you do is enter an energy amount in kWh and a time variable in hours, minutes or even seconds.

You can also do it the old-fashioned way:

1. Multiply the energy in kilowatt-hours (kWh) by 1,000 = watt hours
2. Divide the resulting watt hours by the time in hours = watts

How can you calculate the energy cost of an appliance?

With a basic understanding of watts, kilowatts and kilowatt-hours, you can begin to approximate the amount of energy a given device or appliance uses and how that usage contributes to your electricity bill.

Here’s an example. Let’s suppose you have a 2,500 W clothes dryer you use for 2 hours a day:

1. Divide the dryer’s wattage (look for a product label) by 1,000 to calculate kW.
   2,500 / 1,000 = 2.5 kW
   
   
2. Multiply the kilowatts by the hours of daily use
   2.5 kW x 2 hours = 5 kWh per day
   
   
3. Estimate a month’s dryer usage
   5 kWh x 30 days = 150 kWh per month
   
   
4. Now multiply the kWh per month by your energy rate, which you can find on your bill.

The result is an approximation of how much it costs to power your clothes dryer in an average month. Perform this simple calculation for other appliances you use frequently, and you’ll see how they contribute to your electricity bill, and how you can adjust your usage to lower your bill.

Also, keep in mind that a home’s air-conditioning and heating system (AC especially in Texas!) is likely the biggest contributor to your electricity usage.

How many watts do residential solar panels produce?

Rooftop solar can be a powerful choice for homeowners looking to increase their energy independence and do their part for a cleaner future. Along with helping to power a home, the energy generated from rooftop arrays can be stored for future use and even returned to the larger electric grid for incentives such as bill credits.

But how much energy can a homeowner generate via rooftop panels? According to Forbes Home ⁱⁱ, a standard rooftop solar panel can generate 250-400 watts per hour. Or, expanding further:

• 250 – 400 watts per hour
• 1.5 – 2.4 kilowatt hours per day
• 10.5 – 16.8 kilowatt-hours per week
• 546 – 874 kilowatt hours per year

Using the rated wattage of a solar panel, it’s easy to determine how much electricity a solar panel can produce:

• Power in watts x average hours of direct sunlight = daily watt-hours

Of course, there is a huge number of factors that influence a rooftop array’s potential for energy production. These include the specific type of solar panel, orientation, system design and efficiency, climate and amount of sunlight, just to name a few.

How many kilowatts should a generator be to run a house?

According to “Your ultimate guide to home backup generators,” the key to generator sizing is knowing the power requirements of your home appliances and devices. Here’s an excerpt:

Begin with a list of the appliances and systems you want to keep powered during an outage. That probably includes essential lighting, refrigeration, heating or cooling systems, communication devices and vital medical equipment.

When you know the start-up and running wattage needs of these essentials, you'll have a good starting point for your generator’s needed capacity. Of course, you can always begin the process by consulting with a professional.

The capacity of a generator can also be approximated based on home size. Here are some guidelines from Generac:

• 14kW generator system for a 1,000 - 2,000 sq ft home
• 18kW generator system for a 2,000 - 3,000 sq ft home
• 24kW generator system for a 3,000 - 4,000 sq ft home

Measuring your energy use is simple with a smart meter

The days of meter readers manually recording a home’s electricity usage are largely behind us. Today’s smart meters transmit data to your providers and make it easy to know precisely how many kWhs you’re using in a given month or even on a single day. Thanks to smart meters, it’s easier than ever to monitor and manage your energy usage.

Empowering your energy management

Recognizing the relationship between electricity-related terms and your real-world energy usage is one way you can take more control of your efficiency and potential savings. When you choose Reliant as your electricity provider, you’ll also have access to a toolkit of industry-leading innovations that can take your energy management to the next level.

• Online account management – Your account command center, where you can track usage, view plan details, access special account
   
  
• Reliant app – The on-the-go tool that makes it easy to manage usage, pay your bill and even monitor your solar impact from anywhere
  
  
• Weekly Summary Email – Check your inbox for detailed usage data, bill projections and custom efficiency tips
  
  
• AccountAlerts – Get the energy info you need in an instant via text message, plus set up automatic alerts

ⁱ Inch Calculator: Kilowatt-Hours (kWh) to Watts Conversion Calculator

ⁱⁱ Forbes Home: May 2024, How Much Power Does a Solar Panel Produce?