Amid growing concerns about rising energy prices, energy independence, and the impact of climate change, statistics show buildings to be the primary energy consumer in the U.S. This fact underscores the importance of targeting building energy use as a key to decreasing the nation's energy consumption. The building sector can significantly reduce energy use by incorporating energy-efficient strategies into the design, construction, and operation of new buildings and undertaking retrofits to improve the efficiency of existing buildings. It can further reduce dependence on fossil fuel derived energy by increasing use of on-site and off-site renewable energy sources.

The concept of a Net Zero Energy Building (NZEB), one which produces as much energy as it uses over the course of a year, recently has been evolving from research to reality. Currently, there are only a small number of highly efficient buildings that meet the criteria to be called "Net Zero". As a result of advances in construction technologies, renewable energy systems, and academic research, creating Net Zero Energy buildings is becoming more and more feasible.

As the "zero energy" and "net zero energy" concepts are relatively new, there are not yet definitive, widely accepted zero-energy metrics. The Department of Energy (DOE) and the National Renewable Energy Laboratory (NREL) have spearheaded much of the work on net zero energy buildings to date. NREL presents several definitions for "net zero energy", and they encourage building designers, owners, and operators to select the metric that best fits their project. NREL presents several definitions for "net zero energy", and they encourage building designers, owners, and operators to select the metric that best fits their project. The NREL publication Zero Energy Buildings: A Critical Look at the Definition explores definitions in detail, and it suggests four ways in which net zero energy may be defined:

Site Energy refers to the energy consumed and generated at a site (e.g. a building), regardless of where or how that energy originated. In a net zero site energy building, for every unit of energy the building consumes over a year, it must generate a unit of energy.

Source Energy refers to primary energy needed to extract and deliver energy to a site, including the energy that may be lost or wasted in the process of generation, transmission and distribution. For example, a coal-burning power plant may generate 1 Joule of electricity for every 3 Joules of energy in the coal consumed. If natural gas is used at a site, for every 20 Joules consumed, 1 Joule may be needed to extract and distribute the gas to the site. Metrics for net zero source energy buildings account for these factors, though exact metrics can vary depending on site and utility factors.

Net Zero Energy Cost is perhaps the simplest metric to use: it means that the building has an energy utility bill of $0 over the course of a year. In some cases, building owners or operators may take advantage of selling Renewable Energy Credits (RECs) from on-site renewable generation.

Many conventional energy sources result in emissions of carbon dioxide, nitrogen oxides, Sulphur dioxide, etc. A Net Zero Energy Emissions building either uses no energy which results in emissions or offsets the emissions by exporting emissions-free energy (typically from on-site renewable energy systems).

Two milestones for NZEB have also been defined by the Department of Energy (DOE) for residential and commercial buildings. The priority is to create systems integration solutions that will enable:

These objectives align with the Energy Independence and Security Act of 2007, which calls for a 100% reduction in fossil-fuel energy use (relative to 2003 levels) for new Federal buildings and major renovations by 2030.

The Building Technologies Office (BTO), created under DOE's Office of Energy Efficiency and Renewable Energy, focuses on improving the efficiency of buildings and their associated equipment, components, and systems. The BTO supports research and development activities, tools, guidelines, training, and technical resources to improve new and existing building performance in both the Commercial and Residential sectors. A Multi-Year Program Plan for the BTO outlines the projected activities and near-term goals of the BTO, including both commercial and residential building research focused on achieving long-term Net Zero goals.

The Net Zero Energy Commercial Building Initiative (CBI) aims to achieve marketable net zero energy buildings by 2025 through an array of public and private partnerships to advance the development and adoption of high-performance buildings.

Parallel residential initiatives are conducted under the Building America Program, which has demonstrated market transformation through research conducted under the BTP. (See the Additional Resources section for links to reports, codes, design guides, software tools, and other key resources to achieve energy reduction and net zero energy strategies available through DOE.)