Method: every case study states what was measured, over what period and at what scope. Percentages from different bases (buildings vs. households) cannot be added together or interchanged. Signed client confirmations are available to public contracting authorities; the remaining case studies we evidence by measurement. ⚠ For supplies and services the procurement rules ask only for a list of references (Art. 58(4) and Annex XII of Directive 2014/24/EU) — a signed confirmation is more than the law requires.