Zero (net) energy (ZE, ZNE) – building something that produces enough energy onsite to meet its own needs on an annual basis – is a “sticky” idea. People grasp it, and they like it; it’s captivating and motivating. What’s the power of ZE? It evokes self-sufficiency, and for many, fairness – taking no more than their share of resources. It’s also a specific, concrete goal, not an abstraction like “green” or “energy-efficient” (as compared to what?). And it’s a major accomplishment, a satisfying outcome for one’s efforts. This year’s inventory bears out the allure of ZE, showing a growth rate in 2017 more than double that of 2016 – last year saw a 70% increase in ZE housing units, versus a 33% increase in 2016 over our baseline 2015 inventory.