Striving for net-zero energy usage for commercial and residential buildings can greatly reduce the nation’s energy consumption. When you combine commercial and residential buildings in the United States, this sector represents 38.9% of total energy use in the United States, according to the 2017 Energy Information Administration report. This statistic highlights the importance of buildings taking ownership of their energy usage and making their way to become a net-zero energy building.
This blog post is the first of four articles discussing the importance of net-zero energy usage. Over the next few weeks, we will discuss what net-zero energy usage is, how to get there, and why it’s important.
How Do You Define a Net-Zero Energy Building?
The definition by the U.S. Department of Energy, states that a net-zero energy building is a residential or commercial building with greatly reduced energy needs. This type of building operates at a level of energy efficiency so high that the balance of energy needs can be supplied with renewable energy technologies.
According to a whitepaper by the U.S. Department of Energy, net-zero energy buildings can be put into four different classifications based on the renewable sources a building uses. The purpose of this classification is to encourage building owners to use all possible cost-effective energy efficiency strategies and then turn to renewable energy sources and technologies that are located in the building. Once these options are fully exploited, then a building should turn to off-site options.
If you are interested in some of the latest renewable energy technologies, check out these blog posts.
How is Net-Zero Energy Buildings Classified?
Here are the four types of Net-Zero Energy Buildings (NZEB). The classifications are listed in the order of preference, the first being the most recommended.
- Buildings that offset all its energy use from renewable resources that are available within the footprint.
- Buildings that generate and use energy through a combination of energy efficiency, renewable energy generated within the footprint, and renewable energy generated within the site. These buildings can qualify as sites because of their use of on-site renewable energy resources.
- Buildings that use renewable energy strategies as described above to the maximum extent feasible. These buildings also use off-site renewable resources that are brought on-site to produce energy.
- Buildings use the energy strategies described above to the maximum extent feasible. These buildings also use a fourth option, purchasing certified off-site renewable energy such as utility-scale wind and renewable energy certificates from certified sources. This type is the least recommended and often discredited because it only leaves a paper trail of NZEB. Overall, this method isn’t great for the grid and doesn’t benefit the environment.
How is Net-Zero Energy Calculated?
Now that we defined net-zero energy, let’s clarify how to calculate it. Again, a net-zero energy building is one that produces on-site at least as much energy as it uses. The U.S. Department of Energy has been mulling over the various ways to define and calculate zero energy use and in 2015 they made their choice. The final decision was to go with a zero energy balance based on source energy.
What is the Difference Between Source and Site Energy?
Here are the definitions of source and site energy according to an article by Energy Vanguard.
- Site energy: This is the energy used on-site, as measured at the meter. For electricity, just look at the kilowatt-hours you get billed for.
- Source energy: This is the energy used on-site plus the energy that went into getting that energy onto the site. For electricity, it’s the kilowatt-hours you get billed for plus the kilowatt-hours of energy that are “consumed in the extraction, processing, and transport of primary fuels such as coal, oil and natural gas; energy losses in thermal combustion in power generation plants; and energy losses in transmission and distribution to the building site.” That quote is from the DOE report, A Common Definition for Zero Energy Buildings, released in September 2015.
For More Information
For more information on net-zero energy buildings and for a longer explanation on how to calculate it, check out our blog posts that will be going out next week. If you are interested in reading more content similar to this one, check out these blog posts. For any other energy needs, contact us!