Eco homes are often referred to as being ‘Zero Carbon’, ‘Net Zero Carbon’, or even ‘Zero Carbon Ready’ so what do these terms mean? The term ‘Zero Carbon’ is used to describe buildings where the operation of the building does not result in any carbon emissions. Since only a third of electricity is generated from renewable sources in the UK, for homes to be truly ‘Zero Carbon’ today, they must be completely off-grid and generating all their own energy on-site. The term ‘Zero Carbon Ready’ refers to the notion that a building can be built in such a way that it will become ‘Zero Carbon‘ once the electricity grid fully decarbonises. The term ‘Net Zero Carbon’ refers to buildings where all carbon emissions resulting from the operation of the building are offset by renewable energy provision, either on-site or off-site. It should be noted that all these terms relate to carbon emissions resulting from the operation of buildings and do not include emissions resulting from the construction of buildings (i.e. embodied energy).