A "zero net" home is a household with zero net energy consumption and zero carbon emissions annually -- essentially, the idea of a zero net home is a building with a virtually invisible carbon footprint. As renewable and clean energy sources become more affordable and accessible to everyday homeowners, we should hopefully see an increase in both zero net homes, and homes that consume slightly more energy than they produce, commonly called "near-zero energy buildings" or "ultra-low energy houses". Carbon emissions have been dropping a little in recent years, but humanity still has a long way to go, and more zero net and ultra-low energy households offer a possible next step.
Beyond merely reducing carbon emissions, zero net energy buildings would also effectively reduce (and one day help eliminate) our dependence on fossil fuels; traditional buildings consume 40% of the total fossil fuel energy in the US and Europe and are significant contributors of greenhouse gases. Although they are still rare, zero net homes are not as far-fetched as one might think — and they might even be a necessity in the near future.