The CCHP system driven by biomass energy is essential for mitigating the fossil energy crisis and reducing CO2 emission. But few research work focuses on the micro-scale system due to the limited efficiency. In this paper an efficient household CCHP system is designed, which is driven by the water steam (100 degrees C-120 degrees C) from the biomass boiler and is consisted of an R245fa power cycle with a gravity assisted thermal driven "pump", a single-pressure R134a/DMF/He diffusion absorption refrigeration cycle, and several heat exchangers for heating supply. The models of the system are constructed, and the energy, economic and environmental indexes are evaluated. The results reveal that the higher temperature of heat source and the lower temperature of ambient could improve the thermal efficiency of the CCHP system, and realize the lower cost and CO2 emission. The highest thermal efficiency of the CCHP system can reach to 55.26%. The quarterly energy saving for summer of a 100 m(2) isolated house of a rural family can reach to 5059 kW.h (497 kW.h for cooling, 3154 kW . h for heating and 1408 kW.h for power generation), which can save about 3121.40 RMB electricity bill and reduce 0.15 t CO2 emissions. (C) 2020 Elsevier Ltd. All rights reserved.