## 4 Simulation Results  
### Economic Assessment  
The simulation results of five systems with different configurations (including ASHPs, GB, CHP, domestic electric heater, domestic gas heater) are presented and compared. Gas price is USD 0.539/m\({}^{3}\). The time-of-use electricity price is implemented in China. Peak electricity prices, flat electricity prices, and off-peak electricity prices used in the baseline scenario are USD 0.167/kWh, USD 0.101/kWh, and USD 0.048/kWh, respectively. To provide a realistic comparison, the heat loss and AHUE of each configuration is considered. Importantly, each proposed DHW is based on comparison with the same hot water demand. Moreover, each DHW system operates at rated power, with the same hot water temperature and no change in heat flow. Figure 2 shows the high initial investment with CHP. The highest initial investment of CHP remains a large obstacle to applying residential than other configuration of home appliance. Whether it is centralized DHW or distributed DHW, CHP has no advantages on the initial investment. The calculation of investment of different DHW system is from Equation (7). Meanwhile, the DHW system, GB and CHP, refers to the heat transmission and distribution system with more end-users. Use the transmission and distribution pipe network to connect heat users and heat sources to meet local hot water demand. The DHW system, which includes ASHP, domestic gas-fired heater and domestic electric hot water-heater, refers to a heating way by home appliance to meet domestic hot water demand. The DHW system requires longer pipe and consumes more energy than a DHW system in the same demand for hot water. However, the operation costs of a DHW system are low. This paper analyzed the economy of various energy systems. AHUE describes the actually usable and flows into pipeline, taking into account the heat loss of pipeline and gas combustion losses. Through the simulation by the obtained heat data, the AHUE of the CHP system is 31.84% with the heat output efficiency and power output efficiency of 51.5% and 33.5%. The AHUE comparison with different system is shown in Figure 3, which are calculated by Equation (13). The main reason is that the end-users of the selected buildings stay in the building for a short time, the DHW load of the building does not take large portion. In simulation, the heat output is calculated by the same hot water demand and AHUE of each configuration. Figure 4 represented the monthly hot water demand. Energy consumption of hot water in winter season is greater than that in summer season, because  
Figure 2: The investment of different DHW system  
the supply tap water temperature and outdoor air temperature [26] changes according to the seasonal temperature. The lower heat load in February is due to the Chinese New Year, as most people had left the building. Figure 5 shows the annual energy consumption for each configuration. The annual energy consumption and power saving cost are calculated by Equations (8) and (11), respectively. The micro-CHP, and gas heater is supplied by natural gas, and the rest of the equipment is supplied by electricity. The annual investment cost of different DHW systems is calculated by Equation (7), according to initial investment, interest rate and engine lifetime to eliminate the impact of lifetime. The annual operation of domestic electric heater is too high compared with the traditional system (GB). However, the domestic gas heater on DHW system and CHP on DHW system seems to be an alternative from an economic point of view as well as an engineering one. Figure 4: Monthly hot water demand with building. Figure 5: Annual energy costs and power saving cost with different DHW system. Figure 3: AHUE and steady-state efficiency in DHW system of the building.