Mentioning it just because I didn't see it addressed in the article: AC compressors & fans can be a significant current draw. If you want to replicate this project, it's probably worth checking the amperage ratings for whatever smart plug you use. Something intended to switch lights or a room fan may not be up for the task of repeatedly starting a compressor. Even if the AC unit only draws 15 amps (an so is fine to plug into a wall), inrush current could be an issue for an traic or SSR-based smart plug.