The economic efficiency under varying load operation of ultra-supercritical units has been studied. Under condition of same load factor of peak-regulating

the economic efficiency of ultra-supercritical units is higher than that of supercritical and subcritical units. In the event of reducting load in operation of ultra-supercritical units to 60% of their rated load

the specific heat consumption of said units will be lower than that of supercritical 600 MW units under rated operating condition; in case the load of untra-supercritical units is lower than 40% of their rated load

the designed value of their specific heat consumption will be lower than that of subcritical 300 MW or 600 MW units under rated operating condition; after the load of ultra-supercritical units is lower than 60% of their rated load

their specific heat consumption has a tendency of accelerated rise. Hence

it is recommended that the ultra-supercritical units should be ensured being operation under higher load as far as possible

the economic load of ultra-supercritical units shouldn’t be less than 60~70% of their rated load.