Steam generators boil water to produce steam. Older steam generators are also known as boilers.

Wherever in the HVAC process steam is required, a steam generator is used. Steam generators were an essential component of locomotives in the early days of the railroad; however, the steam generators we are probably most used-to today are stationary boilers made for domestic application to provide heat, hot water, or steam. These are often called hydronic boilers, and are quite common in Europe.