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kW vs. kWh: What's the Difference?

Understanding energy usage and the costs that come with it is becoming more important. One area that often leads to confusion is distinguishing between kilowatts (kW) and kilowatt-hours (kWh). This article aims to provide clarity by outlining their core differences and providing practical insights. 


What is a kilowatt (kW)?

A kilowatt (kW) is a unit of power and it measures how much power a specific appliance consumes while it is being used. One kilowatt is equal to 1,000 watts. This is what we usually see on appliances. For example, a 1kW electric heater consumes 1kW of power when it is being used. 

What is a kilowatt-hour (kWh)?

A kilowatt-hour (kWh), on the other hand, is a unit of energy. It measures how much energy is being consumed over a period of time. With the element of time, it is basically generated from the formula of Power x Time = Energy, with Power being the kW.

Based on our example, above, an electric heater consumes 1kW of power when it is used. If it is running for 5 hours, then it consumes 5kWh of energy. If it runs for 10 hours, then it consumes 10kWh of energy. 


When you receive your electricity bill, it's typically measured in kilowatt-hours. This is because it tells you how much electrical energy you've used over a specific period, often a month. The cost of electricity is usually based on the number of kWh you've consumed.


What is the main difference between a kW and a kWh?

The main difference between these two units is what they measure. In the simplest of terms:

  • A kilowatt measures power. Think of it as the speed at which energy flows at a particular moment.
  • A kilowatt-hour measures energy over time. Think of it as the cumulative quantity of energy used over a period.

How do you calculate kW?

To calculate kW, you need to know the electrical power of a device or system, usually provided in watts (W). You can convert watts into kilowatts simply by dividing by 1,000 because 1kW = 1,000 W.

kW = W / 1,000


Example: If you have a 1,500-watt device, the calculation would go like this:


kW = 1,500 W / 1,000 = 1.5 kW

So, the device consumes 1.5 kilowatts of power.


How do you calculate kWh?

Calculating kWh requires two pieces of information: 

  • the power rating in kW 
  • the time in hours that the device is operating. 

Here’s the formula—it’s also very straightforward:


kWh = kW x hours

Example: If you have a 2 kW electric oven running for 3 hours, the calculation would be:


kWh = 2 kW x 3 hours = 6 kWh

So, the electric oven consumes 6 kilowatt-hours of energy during its 3-hour operation.

Why is it important to understand both kW and kWh?

Understanding the power rating (kW) is important because it helps you determine the capacity of circuits and systems to handle the electrical load. It also plays a crucial role in sizing generators and assessing the performance of electrical equipment.


Meanwhile, understanding the kWh is essential for tracking energy usage, managing your electricity costs, and setting energy-saving goals. Electricity providers usually charge based on energy consumption, which is measured in kWh. The more energy you use, the higher your bill will be. 


Additionally, being aware of your kWh usage can help you take control of your energy bills and reduce your carbon footprint. By tracking your usage, you can make informed decisions on energy efficiency and sustainability.


Why is my kWh usage so high?

High kilowatt-hour (kWh) usage can be due to various factors, and understanding why your kWh usage is elevated is crucial for managing your energy consumption and reducing costs. 


Here are common reasons why your kWh usage might be high:


  1. Inefficient appliances. Older or inefficient appliances, such as refrigerators, air conditioners, or water heaters, may consume more energy than their modern, energy-efficient counterparts. Additionally, appliances that may have issues can also cause spikes in energy consumption. If this continues to go unnoticed, energy bills will continue to rise.

  2. Heating and cooling systems: Heating and cooling your home or business facility, especially in extreme weather conditions, can lead to high energy usage. 

  3. Unoptimized thermostats. Not using programmable thermostats or not setting them at energy-efficient temperatures can cause your HVAC system to run unnecessarily.

  4. Multiple appliances simultaneously. Running multiple energy-intensive appliances simultaneously, such as a dishwasher, oven, and air conditioner, can significantly raise your kWh usage.

  5. Energy vampires. Devices that continue to draw power even when turned off (like standby mode on electronics) can add up over time.

  6. Weather. Extreme weather conditions, be it hot or cold, can cause your HVAC system to work harder, resulting in higher energy consumption.

Why should business owners know the difference between a kW and a kWh?

Business owners should be well-versed in the difference between a kilowatt (kW) and a kilowatt-hour (kWh) for several important reasons:


  • Cost management: Business owners can monitor their energy consumption and track energy costs accurately so they can make informed decisions about resource allocation and budgeting.

  • Energy efficiency: Knowledge of kW and kWh enables business owners to identify areas where energy efficiency improvements can be made. By reducing energy consumption, businesses can lower their electricity bills and increase profitability.

  • Load balancing: Businesses often have multiple electrical devices and systems operating simultaneously. By understanding kW, business owners can balance the electrical load to prevent overloading circuits and ensure the reliability of their electrical infrastructure.

  • Sustainability goals: Many businesses are starting to commit to sustainability and reducing their carbon footprint. Understanding kWh usage is crucial for tracking progress toward sustainability goals and adopting renewable energy sources to decrease environmental impact.

  • Compliance and reporting: In some industries, like the restaurant industry, businesses are required to report and comply with regulations related to energy usage and emissions. Accurate monitoring of kW and kWh data is vital for meeting these obligations.

How can business owners reduce energy usage?

There are a number of ways for business owners to reduce their energy usage. 


  1. Upgrade to energy-efficient appliances. Replace old appliances with energy-efficient models and look into investing in other renewable energy sources. 

  2. Use smart thermostats. Invest in programmable or smart thermostats to optimize heating and cooling, especially during peak hours and off-peak periods. That way, you’re not consuming more than what you need.

  3. Conduct an energy audit. Before making any big investments or moves, consider hiring a professional to conduct an energy audit of your business facility to identify specific areas for improvement.

Explore how GlacierGrid's Smart Building Solution elevated energy efficiency at a McDonald's franchise.


Additional resources

For more information on tracking your kWh, energy cost savings, and sustainability, you can explore the following resources: