The after-market labeling of a device by its users often indicates problematic usability, which can affect the device's energy consumption. For example, when people find a lighting control panel difficult to use, they often write instructions on a piece of paper and affix it nearby as a reminder to themselves and to help others. We collected over a hundred examples of these “folk labels” from commercial and residential buildings through an online contest inviting people to upload photos of folk label examples, informal solicitation of colleagues, online searches, and personal observation. Some folk labels offered guidance or reminders (e.g., turn off light before fan on a projector); some provided specific instructions for multi-function controls or addressed problems identifying orientation or direction (right/left, on/off). We categorized these folk labels (e.g., by location, subject, form, etc.), and analyzed them according to usability guidelines and heuristics1 . In addition, we evaluated their potential impact on energy consumption. We found that most folk labels indicated usability issues in three areas: visibility of available options, natural mappings, and consistency. For example, one light switch looked like a simple toggle ON-OFF control, but actually could control various dimming options (violated “visibility of available options” principle). One would naturally turn the light on full power if one did not know how to use the dimming capability. We discovered that folk labeling provides a simple means of identifying usability problems.