EXCESS defined a positive energy building (PEB) as a building that produced more energy than it used, with a high renewable energy source (RES) self-consumption rate (instead of using the grid for solving seasonal balancing issues) over a time span of one year.

RES and smart technologies existed, but complete packages for different climates did not. Important technical developments for plus energy building materials and other individual technologies were required to address specific climate-related needs in order to meet the PEB level, especially in harsh climates. Integration was needed for upgrading single technologies to be part of a large orchestra, enabling also user-context-aware energy-flexible services between utilities and customers (selling flexibility). These would unlock additional revenue streams that would reduce the lifetime cost of the developed PEB solutions, making them affordable to a large portion of society. Thus, EXCESS advanced new materials, technologies, and integrated technological systems promoting a user-centric approach, capitalizing on new ICT opportunities for optimizing the interplay of local generation, storage, and consumption at the building and district level.

Demonstration activities in each of the climate zones (Austria, Belgium, Finland, and Spain) were accompanied by co-innovation, replication, and exploitation activities to maximize the project's technical, social, and economic impact and to prepare for a future market roll-out of the PEB concept by also scouting energy efficiency funding opportunities.