Boverket (Swedish National Board of Housing, Building and Planning) is the Swedish government agency responsible for issues concerning spatial planning, construction and housing. It is also the supervisory authority for energy performance certificates, ensuring that the requirements of the Energy Performance Certificate Act are complied with and that the certificates are correctly prepared and registered.
The information available in the Boverket API includes:
Energy class (A–G)
Energy declaration ID
Energy performance (primary energy figure)
Specific energy use
Whether radon measurement and ventilation inspection have been carried out
Date of the energy declaration
More information is available at boverket.se.