# Wireless Home Energy Management System with Smart Rule-Based Controller
## 4 Results and Discussion
### AC Unit  
As with the LED light, the operation of the AC unit was based on the room occupancy, as well as the room temperature. Figure 19 shows the power consumptions without and with the use of the HEM system and the corresponding temperature variations. It should be noted that, before the scheduling, the use do not turn off the AC unit even during unoccupied period due to hot climate in UAE. However, the user usually control the AC unit only by just adjusting thermostat set points manually. This is clearly seen in the power consumption pattern and temperature plot represented in the blue line in Figure 19.  
Figure 16: Electricity pricing signals during the use of the home energy management (HEM) system.  
The AC unit was continuously operated until the set temperature was reached, and the compressor was then automatically turned off. Based on the set temperature limits, the unit subsequently alternated between the on and off status to save energy. Under normal energy pricing, the AC was continuously operated, except the consideration of the room occupancy status was manually turned off. However, the HEM algorithm did not allow for the AC to operate until the threshold temperature of the room was reached. Although the temperature threshold varies with the pricing regime (minimum, normal, or maximum pricing), the algorithm was always able to reduce the energy consumption.  
Figure 17: (**a**) Power consumptions of the LED light, room occupancy status and (**b**) illuminance variations without and with the use of the HEM system.  
During non-peak pricing hours, the AC was allowed to operate, provided that the room was occupied and the room temperature was within the preset limits. In addition, the algorithm controlled the AC to maintain the lowest possible temperature during low pricing hours, so it could be turned off during high pricing hours without affecting the user comfort. However, the AC was allowed to maintain the room temperature at the preset upper temperature during the maximum pricing hours, as can be observed from the third graph of Figure 18a. It was turned off more frequently when the room temperature was further below the preset maximum temperature. This can be observed from the noticeably different cycles of the AC compressor during the maximum pricing hours. Despite all of the applied constraints, the HEM algorithm was able to maintain the room temperature within the preset temperature range.  
Figure 18: (**a**) Energy consumptions and (**b**) bills incurred by the LED light without and with the use of the HEM system.  
The room temperature during normal pricing hours was only subject to manual operation of the AC. However, this was dependent on the occupancy of the room when using the HEM system, with the temperature being allowed to rise above the maximum comfort level when the room was unoccupied. Moreover, the preset temperatures for the minimum and maximum pricing hours were the same as those for the normal hours. Figure 20 shows the energy consumption and bill trends of the AC unit.  
The highest amount of energy was used during the minimum pricing hours, which was because the HEM algorithm maximized the AC use at these times, and reduced it during the maximum pricing hours, as can be observed from Figure 19. Overall, the HEM system significantly reduced the daily energy consumption and bill by 13.9 kWh and $1.64, respectively.  
Figure 19: (**a**) Power consumptions of the AC, room occupancy statuses, on/off cycles of the AC and (**b**) room temperature variations without and with the use of the HEM system.