Apply the minimum environmental sustainability requirements where there is a single possible supplier, where a comparable earlier tender drew no suitable bids, or where compliance would cost disproportionately or break technical compatibility.

Contracting authorities and contracting entities may, on an exceptional basis, decide not to apply paragraphs 1 to 4, where: (a) the required net-zero technology can only be supplied by a specific economic operator and no reasonable alternative or substitute exists and the absence of competition is not the result of an artificial narrowing down of the parameters of the public procurement procedure; (b) no suitable tenders or no suitable requests to participate have been submitted in response to a similar former public procurement procedure launched by the same contracting authority or contracting entity in the two years immediately before the commencement of the planned new procurement procedure; (c) their application would oblige that contracting authority or contracting entity to acquire equipment having disproportionate costs or would result in technical incompatibility in operation and maintenance. 10. Estimated cost differences above 20 %, based on objective and transparent data, may be presumed by contracting authorities and contracting entities to be disproportionate.