A power plant’s 600MW subcritical direct aircooled unit jointed grid low load regulation, rang of 50% to 100% rated load. The coal consumption of this unit reaches to 360g/(kW·h) in load operation. To find the causes, thermal performance test, equivalent enthalpy drop and other methods were adopted. The factors that affects economic efficiency in low load was quantitatively analyzed. Treatments to improve operation and economic efficiency was provided. 

aircooled unit, low load, equivalent heat drop, economic efficiency