SEEP defines zero energy (ZE) and ZE-C buildings in the Zero Energy Toolkit as follows:

Zero Energy

A Zero Energy (ZE) building generates as much renewable energy annually as it uses in a year, as measured at the site. ZE buildings do not use fossil fuels and other forms of combustion. ZE is typically accomplished by incorporating energy-efficient design strategies, specifying electric heating and cooling systems, and maximizing roof space available for renewable energy systems (e.g., solar photovoltaic [PV] energy).

Zero Energy-Capable

A Zero Energy-Capable (ZE-C) building is designed to achieve the same level of energy efficiency as a ZE building and is capable of achieving ZE when renewable energy is added in the future. Unique projects with higher process energy use (e.g., laboratories or healthcare facilities) that cannot satisfy all energy needs on-site should be designed to achieve the highest level of energy efficiency that is feasible. Buildings with site constraints that prevent the installation of sufficient solar panels to meet ZE goals may document compliance with EO 20-01 by contacting the SEEP Office. Zero Emissions Capable (ZE-C) means that a building can be powered from clean energy in the future.