A Colorado resident said her internet-connected thermostat prevented her from lowering her home’s temperature during a period of high electricity demand, displaying a message that the local grid was “stressed”. The incident drew attention to concerns about how energy companies can remotely manage customers’ smart devices and the extent to which households understand the terms of such schemes.

The woman’s thermostat was reportedly set at 79°F (about 26°C) and showed that it was in an “energy emergency” mode. Xcel Energy said customers who enrolled in its demand-response programme had agreed to allow temporary adjustments during peak events, and that participants could normally opt out, though the reported thermostat message indicated the setting was temporarily locked.