Roughly 750 Hamburg-based trade companies from the areas of sanitation, heating and plumbing are represented by the SHK e.V. association, which can trace its origins to the 16th century. Installers from these trades take (legally) mandated measures to increase energy efficiency, e.g. renewable energy technologies such as wood pellets or logs and micro CHP plants (combined heat and power). Since May 2011, trainees, journeymen and masters have been taking part in continuing education in these fields in the Renewable Energy Centre of Expertise in Hamburg.