The economizer, also known as an economizer, is a device installed at the lower part of the boiler's tail smoke duct to recover the waste heat from the exhaust gases. It heats the boiler feed water into saturated water under the steam drum pressure, absorbing heat from the high-temperature flue gases, thereby reducing the exhaust gas temperature, conserving energy, and improving efficiency. Hence, it is called an economizer.

Pipe-type economizers are not limited by pressure and can be used for boiling; they are generally made of carbon steel pipes with an outer diameter of 32 to 51 millimeters. Fin and rib attachments are sometimes added to the pipes to enhance heat transfer. The pipe-type economizer consists of parallel bend tubes arranged horizontally (commonly referred to as serpentine tubes).

The economizer is primarily used in industrial settings and is increasingly becoming popular in agriculture and related commercial industries.