## 4 Discussion
### Policy Implications  
Considering the economic and environmental advantages, the CPH technology is strongly advised to serve various types of buildings worldwide. To achieve the maximum benefits from the cogeneration system, several practical suggestions are provided for the installation and implementation of the cogeneration system in real situations:  
First, it was suggested to conduct both economic and environmental evaluations of different CPH technologies rather than conducting only economic or environmental evaluations when selecting the appropriate CPH technology. This is because this approach can provide a comprehensive understanding of the economic and environmental performance of a CPH technology for a certain context [15; 21; 22; 25; 26; 28; 29; 30; 33; 34; 35; 36].  
Second, the use of CPH technology should be promoted for different types of commercial buildings (e.g., hotel, school, small office, and supermarket) as this systematic review found that CPH technology is beneficial to different types of commercial buildings in terms of environmental effectiveness and economic efficiency. Concerned authorities and the government should provide incentive policies or programs to encourage the use of CPH technology for different types of commercial buildings.  
Third, the selection of the proper cogeneration configuration size is a must, especially the size of the generator. The right size will generate the right amount of required energy with minimum losses. The suitable size is determined by the potential site condition and requirement. For example, the installation of the system at a school will encounter some challenges with respect to system sizing, plant selection, energy consumption, financial strategy, government policies, etc. To this point, simulation analysis is a necessary step for cogeneration optimization, e.g., [27; 40; 41].  
Fourth, the selection of a suitable prime movers type is of significance. This is because the specific type of prime mover corresponding to the plant configuration can only allow for a certain amount of energy production in maximum to meet the demands. In this case, it is essential to consider some factors relevant to the prime mover, such as prime mover performance, energy demands, electrical performance, gas emissions, and initial investment (e.g., [15; 30; 42]).  
Fifth, the selection of location should also be considered, which will avoid additional costs either in the initial installation or in future maintenance. To this point, the plant is better to be sited in a place where it can remain for long time without disruption or obstruction, and where it should have a large space for maintenance and/or housing supplementary equipment [28; 40; 43].  
Last, economic strategy is another factor that calls for serious consideration. It is evident that economic investigation is the key to ensuring the success of the system's installation and implementation. Therefore, an appropriate financial method to support the project is the objective. The economic strategy relies on the state of the candidate's profile, the government-supported policies (e.g., government subsidy), and other financial supports (e.g., special tariff system) [14; 23; 25].