# A Review of Systems and Technologies for Smart Homes and Smart Grids
## 5 Review of the Technologies for Smart Homes
### Home Energy Management  
Development of the home energy management system (HEMS) started due to the energy shortage and the effects of global warming. Since its first application in 1976 [67], it has become one of the most popular research topics. The HEMS allows the energy usage of a building to be managed and controlled automatically and helps reduce peak demand for electricity and users' electricity bills [41]. The number of HEMS installations is rising in areas of North America and Europe that have a high latitude, because of the number of hours of darkness each year. In those areas, the HEMS reduce quite significantly the total electricity demand: up to 30% of the electricity load takes place during peak hours. The peak load can be reduced by, on average, 30% and the operational cost of electricity by 23% [68; 69; 26]. In smart grids, the use of energy management systems has become a priority to distribute locally the energy generated by users according to the prices of the energy, which is regulated by daily rates. A future trend might be operating using specific hourly rates, _i.e._, real time pricing (RTP), time of use (ToU), inclining block rates (IBR), critical peak pricing (CPP) _etc._  
If this method is used, the HEMS will improve the number of products that customers could use to perform daily tasks such as viewing data on energy usage, controlling thermostats, and individual home appliances, looking at tips on ways to save energy, manage a profile for participation in demand-response programs, and viewing their account and billing information. According to [PERSON] _et al._[69] and Green Tech Media [70], all types of products available on the residential market can be divided into three categories (control devices, graphical user interfaces, and enabling technologies) that include the fundamental aspects summarized in Table 3.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Category** & **Technology** & **Description** & \multicolumn{1}{c}{**Examples**} \\ \hline \multirow{8}{*}{Control devices} & \multirow{4}{*}{Centralized} & It allows communicating with multiple appliances in the home environment. The users can manage them a single location and often using multiple inputs & \(\bullet\) & Home automation (HA) systems; Whole-home lighting control systems; Security systems \\ \cline{2-4}  & & & \(\bullet\) & Security systems \\ \cline{2-4}  & & & \(\bullet\) & Lighting control with motion sensors, dimmers, remotes, scheduling; Thermostats; Smart plugs; Smart power strips \\ \cline{2-4}  & & & \(\bullet\) & Smart appliances, e.g., that respond to grid; Office equipment power management; Smart light bulb \\ \hline \multirow{8}{*}{Graphical User Interfaces} & Home Energy Display & Stand-alone in home display; often portable & \(\bullet\) & Many HEDs on the market have compatible web dashboards or are able to connect to third party freeware \\ \cline{2-4}  & & & \(\bullet\) & Utilities implementing smart meters often provide their customers with web dashboards \\ \cline{1-1} \cline{2-4}  & & & \(\bullet\) & Current products typically pull information from a home energy display and generates processed data; \\ \cline{1-1} \cline{2  
The advantages of the HEMS are:  
1. The increased savings for both users and utilities providers;
2. A reduced peak-to-average ratio and peak loads;
3. They can include local energy production from renewable sources;
4. They allows the household to be inserted in a systemic context, as a separate local grid, and allow it to be connected to the outside world, _i.e._, creates a smart grid;
5. They allow for historical comparisons of home energy usage. The use of a centralized control function for the user interface, which includes a control for the use of appliances, is recommend and it would be useful to educate the end-users on how to use the integrated automated controls systems to avoid having automation that the end-users do not know to operate properly.