Drought and population growth, especially in the western United States, are propelling a need for more efficient irrigation. Smart irrigation controllers, which interface with soil moisture, evapotranspiration (ET), or weather sensors, have been promoted as a demand-side management tool for this purpose. This paper reviews the body of research on residential smart irrigation controllers and their effectiveness. We find that smart irrigation controllers consistently reduce water demand by 15% among general users and more than 40% among indulgent users. Gaps in research include studies addressing peak demand reduction, centralized communication, data verifiability, and human factors of landscape management. Future work may develop techniques for coordinating networks of smart irrigation controllers to enable greater shifting and shaving of discretionary irrigation demands, similar to what is already happening in the electric grid, thereby creating an integrated water distribution system (IWDS). An IWDS may utilize smart irrigation controllers as direct load control devices at customer end points and interface with advanced metering infrastructure (AMI) and supervisory control and data acquisition (SCADA) systems at a central location to create more effective demand-side management (DSM) strategies for water conservation.
Weather-based irrigation controllers (WBICs) have become the prevalent smart controllers used for residential irrigation scheduling. They are easy to install, have smartphone control, are easy to program, utilize local real-time weather data, prevent operating the irrigation system during rain or other adverse weather events, adjust watering schedules and duration seasonally, conserve water, and reduce water billing costs. In addition to the ease of use and benefits at the residential user level, smart irrigation controllers have the potential to provide the water utility with controls to buffer or shift peak irrigation demands. This buffering and shifting of peak demands have the potential to lower energy costs, decrease the carbon footprint, and delay costly infrastructure upgrades. With technological advancements and the proliferation of smart controllers, the future for water utilities will become more similar to the electrical grid industry. The smart controllers and technology will enable the development of the IWDS. The IWDS will allow the water utility to utilize data from AMI meters, SCADA systems, smart irrigation controllers, artificial intelligence, and other smart technology to operate more effectively and efficiently.