A feasible variant of the equation is proposed to relate the efficiency of a turbine plant to the kinetic energy of the gas/steam flow: eta(i)= 1/[(1 /eta(min))-(Delta P-use+Delta P-fr)(i)/Delta P-inert], where eta(i)=turbine plant efficiency in an i state (T-t,P-i); Delta P-use, Delta P-fr=kinetic energy of the moving flow used on carrying out effective work and used on overcoming friction between the jets of gas and between the friction parts of the turbine, respectively; q(min)=minimum efficiency attained at a given temperature of the gas flow; Delta P-inert=kinetic energy of the moving flow used on overcoming the inertia forces of the turbine. Employment of abovementioned equation in processing experimental data makes it possible to estimate eta(min), as well as Delta P-inert. The equation facilitates functional monitoring of an operating turbine cycle and can be useful in upgrading and optimizing individual units or in designing new turbines.