The goal of this study is the derivation of evaluation criteria for effectiveness of variable speed circulators used in heating and cooling systems. Proportional pressure control mode has been analyzed as a criterion for centrifugal pumps. For this reason, a great number of energy analyses have been realized for different pumps and a regression equation with a corresponding coefficient of determination has been derived. As the result, the trend of reduction of energy consumption has been determined if the proportional pressure control mode is used in comparison with constant differential pressure control mode. The control modes are compared if the value of the duty point remains invariable for both modes. It has been found that the reduction of annual energy consumption can be achieved up to 33% if the proportional pressure control mode is applied with the deviation of 60% from the head value of duty point at zero flow. There is also the change of efficiency level of circulators has been investigated in the article. It has been done at different deviations from nominal pump head. The regression equation with coefficient of determination has been derived. Finally, it has been derived that the efficiency level drops up to 3% if variable speed centrifugal pumps are applied, and the deviation of the head value of best efficiency point (BEP) is up to 30% from its nominal value. A slight decrease of efficiency level is observed if the deviation from the nominal head value is up to 30%. If the head deviation is above 30% from its nominal value, then the efficiency level drops rapidly.