Production Support Systems (PSS) in the chemical factory are considered to contribute to improved productivity and increased sales of products by speeding up production. Recently, however, doubt has been cast on the cost-efficiency of investment in these systems, so the introduction of new PSS and development of new functions have been slowing down. Nevertheless, PSS based on process systems engineering are expected to play important roles in raising the productivity of chemical factories and it is not desirable to suspend the development of the basic functions of PSS. In this paper, a new criterion of efficiency based on labor-saving effect is proposed instead of the conventional estimate of return on investment in PSS. In order to explain the procedure, an example of the estimation for a chemical process is shown.