What is a Zero Energy or Positive Energy House?

A Zero Energy house is a home which balances out energy consumption with local production, either from solar and/or wind. A positive energy house will produce more energy than it uses, and will typically sell this back to the national grid. It is common for a certified Passive House to be upgraded to a Zero Energy House, as the base energy load for the home has already been reduced by about 80%, requiring significantly smaller local energy production.