A zero energy building (ZEB) or net zero energy building is a general term applied to a building's use with zero net energy consumption and zero carbon emissions annually . Zero energy buildings can be used autonomously from the energy grid supply – energy can be harvested on-site . The net zero design principle is overlaid on the requested comfort of the building occupant . Generally, the more extreme the exposure to the elements the more energy is needed to achieve a comfortable environment of human use . Energy use can be measured in different ways (relating to cost, energy, or carbon emissions) and, irrespective of the definition used, different views are taken on the relative importance of energy harvest and energy conservation to achieve a net energy balance . Although zero energy buildings remain uncommon in developed countries, they are gaining in importance and popularity . The zero-energy approach has potential to reduce carbon emissions, and reduce dependence on fossil fuels . Most ZEB definitions do not include the emissions generated in the construction of the building and the embodied energy of the structure . So much energy is used in the construction of a new building that this can dwarf the operational energy savings over its useful life . Despite sharing the name zero energy building, there are several definitions of what ZEB means in practice, with a particular difference in usage between North America and Europe . Zero-energy neighborhoods, such as the BedZED development in the United Kingdom, and those that are spreading rapidly in California and China, may use distributed generation schemes . This may in some cases include district heating, community chilled water, shared wind turbines, etc . There are current plans to use ZEB technologies to build entire off-the-grid or net zero energy use cities . .