Zero energy buildings, or zero net energy buildings, are constructed to successfully operate independent of the normal electric grid. In other words, they provide their own power through renewable energy. The "zero" refers to both energy consumption and carbon emissions -- a zero energy building consumes zero net energy yearly, and produces no carbon emissions since it relies on renewable energy supplies like solar or wind power.
Zero energy homes are specially built to be extremely energy efficient with excellent insulation and techniques like passive solar design. Of course, efficient design is just the start -- the buildings still need power from somewhere. Active solar panels and wind collectors are common solutions, while some buildings use biofuels for heating. Zero energy construction is most efficient in small communities where several homes can benefit from a shared renewable resource.
Building a zero energy home is obviously no easy task. It's not cheap, either, but some governments are slowly moving to support zero energy construction with subsidies to incentivize the green environmental benefits. The U.S. government offers a Solar Investment tax credit of 30 percent off the total system cost, and the state of California offers additional money back for consumers who opt into renewable energy [source: GoSolarCalifornia]. Zero energy is still a niche form of construction with high up-front costs, but the reward is a perfect blend of technology that barely affects the environment compared to today's average construction project.