By considering the hourly match and balance of multi-energy supply and multi-energy demand

the theoretical formulas of the CO_2 emission reduction ratio of the cogeneration systems under different running status are proposed. According to the simulation results

the cogeneration system obtains the maximum environmental benefits at the electric-thermal equilibrium point. When the heat-to-power ratio is less than the critical value

the electricity-tracking mode receives larger reduction ratio. On the contrary

the heat-tracking mode is the better option. Moreover

the qualitative and quantitative analysis shows that

the selection of reference system and determination of utility efficiency are of vital importance to the assessment of the environmental performance. In addition

according the results of the numerical study

the cogeneration system in a hotel building may enjoy satisfied environmental performance

especially in the winter period. Furthermore

the proposed combined mode illustrates better performance than the conventional heat-tracking or electricity-tracking mode.