The existing legal regulation [4,5,6] requires that the construction design of a building should include an analysis of the possibilities of rational use of renewable energy and heat sources. The Construction Law [6] and the Regulation on technical conditions that buildings should meet [4] do not contain a formulation of this obligation in relation to the building investor, but only to the author of the construction design. This is bizarre because the decision to use renewable heat sources has, in addition to the ecological aspect, a financial aspect. Similarly to solar collectors [1,2], the operation of heat pump installation may be subject to error resulting from the specifics of their operation and diagrams not adapted to the conditions of operation of heat pumps, most often “transferred” from boiler systems. The article indicates typical errors in the conceptual layout of heat pump units, resulting in reduced operational efficiency and increased costs of heating the building and preparing domestic hot water.