What Do kWhth and kWhe Mean?
When discussing heating energy usage, you may see the term “kWhth.” The kilowatt-hour measures how much power is generated or consumed by electronic devices over an hour. One kWh equals 1,000 watts.
While the symbol kW refers to the amount of energy in kilowatt-hours, the subsequent letters tell you what type of energy is being produced.
Thermal energy (th) is written as kWh(th) or as a subscript kWhth. Thermal refers to heat production or reduction, such as when heating a pot of water or cooling your home during the summer.
You may also see the term ‘kWhe’, kWh(e), or kWhe. This is for electrical energy, such as what turns the lights on and powers your TV.
By using these terms, scientists can identify what type of energy is created or used in a system. For example, a small nuclear power station may produce 3 kWhth of heat energy from the reactor, which heats water and creates steam to drive turbines. However, the turbines only produce 1 kWhe, meaning that 2 kWh is lost through electrical generation.
Knowing the difference between these types of energy is important for both energy suppliers and service users. Energy plants can use these distinctions when scheduling around power surges, such as during heat waves. Individuals should understand how the two energy types convert to one another so they can pick energy-efficient appliances.
Why the Distinction Matters in Energy Systems
The kilowatt-hour is an important measure for utility companies and consumers alike, but what form of energy is being used or produced can be critical, too. Here are some of the ways the distinction matters.
Energy Efficiency: The US Department of Energy notes that a heat pump produces two to four times more kWhth than the kWhe that it consumes. Unlike an air conditioner, which turns fuel like gas into electricity, a heat pump transfers heat from one place to another so a room will stay at a comfortable temperature. By factoring in the differences between the two energy types, renewable energy advocates can explain why these energy programs are an economical choice.
Energy Loss: Every energy system will experience some loss, like the turbine example above. Understanding how much thermal energy is needed to create one kilowatt-hour of electrical energy, or vice versa, can help companies design more sustainable products.
Cost Management: Utility companies must calculate how much every customer should pay for their energy usage. Generally, thermal and electrical energy are charged differently. For example, it costs less to watch an hour of your favorite show on your television than to heat the same space. By being conscious of what you are using and when, you can save money on your energy bill.
Resource Management: Keeping the lights on for a whole city takes a lot of energy, and energy needs will vary based on the season. There’s usually a high load on electricity systems during the summer and winter due to higher heating and cooling needs, which can push the electrical grid beyond capacity.
Energy Storage: Thermal energy is much harder to store than electrical energy. This is because it naturally dissipates as heat based on the ambient temperature, and the materials that can provide long-term storage are not always efficient. Additionally, it takes more effort to convert it into another form of energy. Researchers are working to understand how to store this energy so power plants can reduce their expenses and provide better service.
How Are Kilowatt-Hours Used in Practice?
One kilowatt-hour is equal to the amount of energy used in one hour by electrical devices rated at one kilowatt. By adding the correct suffix, the kWh can refer to either electrical (e) or thermal energy (th).
Kilowatt-hours are an invaluable measurement for both residential and commercial contexts. For example, high-voltage appliances generally have a higher wattage and require more energy to run. This can raise your electricity bill and strain the electrical grid. Choosing appliances that don’t need so much electrical energy can help reduce your expenses.
In an industrial context, understanding the relationship between thermal and electrical energy helps power plants determine how to reduce their losses and improve energy efficiency. The heat pump is a great example because it multiplies kWhe into kWhth, saving money and precious resources.
Other Units: MWhth, MJth, and GJth
While kilowatt-hours are helpful in a residential context, power plants and other industrial-scale systems tend to use even larger units. These include the following.
MWhth: One megawatt-hour equals 1,000 kilowatt-hours or one million watt-hours.
MJth: The joule is the standard unit of energy for the International System of Units, which is used throughout the world. One megajoule (MJ) is 1 million joules. To calculate how many kilowatt-hours are in a given megajoule, you simply multiply by 3.6.
GJth: One gigajoule (GJ) is 1,000 megajoules, and one kilowatt-hour equals 0.0036 gigajoules.
These measurements are more convenient for larger organizations because the calculations are not as unwieldy. While your local power plant may use watts and megawatts, international organizations typically use International System of Units (SI) measurements to facilitate collaboration.
Kilowatt-hours can represent either electrical or thermal power, which can be converted back and forth as necessary. Understanding the difference is important for energy conservation, efficiency, and utility management.