User innovation in sustainable home energy technologies

► We clarify how citizen users are able to invent in home heating systems. ► We researched inventions that users did to heat pump and wood pellet burning systems. ► During the years 2005-2012 there were 192 inventions by users in Finland alone. ► Users were able to invent in practically all subsystems of these technologies. ► Users' ability merits policy attention and can lead to new types of policy action.