An excerpt from “NOT Zero Energy” by NRECA’s Keith Dennis, March PUF:
“In the search for a policy that will lower the carbon emissions from buildings, the concept of net zero energy, or interchangeably zero net energy, has emerged as an early favorite.
A zero net energy (ZNE) home is designed to produce as much energy from clean, meaning low or zero-carbon on-site energy sources, as it consumes each year.1 But the simple math of zero-net energy masks fundamental flaws in the concept.
For example, a ZNE home may consume energy during times when energy is in high demand, which may or may not correspond to when the on-site sources are producing energy. Conversely, the home may generate excess clean energy when energy is not needed.
Specifically, a ZNE home may use energy from the electric grid when it is generated by the most expensive and carbon-intensive methods and then export excess solar energy to the electric grid when prices are negative and renewable energy is being curtailed elsewhere on the grid.
In this scenario, as long as the home’s generation amount equals the consumption amount, the home is in compliance with the net zero energy policy. In other words, in the real world, ZNE as a policy strategy, is unlikely to advance the broader goal of carbon reduction.”