The U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE) has embraced the goal of developing net-zero energy buildings (ZEBs) to reduce the nation’s energy demand. In support of this goal, the office created the Building Technology Program to assist in developing technologies and design approaches that lead to economically viable zero energy homes by 2020 and zero energy commercial buildings by 2025.

Photo: Broomfield net zero home, courtesy of Flickr.

The following is a EERE reference guide to net zero energy buildings:

Net Zero Energy Buildings

Net-zero energy buildings are grid-integrated buildings capable of generating as much energy as they consume through advanced efficiency technologies and on-site generation systems. Because net ZEBs meet the balance of energy needs from sources of energy that do not produce greenhouse gases, they therefore result in no net emissions of greenhouse gases.

Net Zero Site Energy

A site zero energy building produces at least as much energy as it uses in a year, when accounted for at the site. The measurement time frame is annual.

Net Zero Source Energy

A source zero energy building produces at least as much energy as it uses in a year, when accounted for at the source. Source energy refers to the primary energy required to generate and deliver the energy to the site. To calculate a building's total source energy, imported and exported energy is multiplied by the appropriate site-to-source conversion multipliers.

Net Zero Energy Costs

In a net zero energy costs building, the amount of money the utility pays the building owner for the energy the building exports to the grid is at least equal to the amount the owner pays the utility for the energy services and energy used over the year.

Net Zero Energy Emissions

A net zero energy emissions building produces at least as much emissions-free renewable energy as it uses from emission-producing energy sources annually. Carbon, NOx, and SOx are common emissions that ZEBs offset.

Near Zero Energy

A near zero energy building produces at least 75% of its required energy through the use of on-site renewable energy. Off-grid buildings that use some non-renewable energy generation for backup are considered near zero energy buildings because they typically cannot export excess renewable generation to account for fossil fuel energy use.

Examples of Zero Energy Buildings

The Zero Energy Buildings Database contains examples of zero energy buildings and details about these projects including:

    * Financing
    * Land use
    * Site description
    * Energy use overview

Visit the ZEB Database to see a sample of zero energy buildings. The EERE also encourages you to submit your own examples of zero energy buildings. If you’re entering a new ZEB, please be sure to include which ZEB definitions you met and how you met them. Also, please include information on the overview and energy pages to show the energy performance of your building.