Rank #3
Use a programmable thermostat to reduce energy use.
This programmable thermostat is a great way to reduce energy use in your home. It allows you to set specific temperatures for different times of the day, so you can save energy when you're not home or when you're asleep. It also has a built-in energy-saving
From Wikipedia
Smart thermostats are Wi-Fi thermostats that can be used with home automation and are responsible for controlling a home's heating, ventilation, and air conditioning. They perform similar functions as a programmable thermostat as they allow the user to control the temperature of their home throughout the day using a schedule, but also contain additional features, such as Wi-Fi connectivity, that improve upon the issues with programming.