Both regular and system boilers store hot water in a cylinder, but they differ in their configuration::* **Regular boiler (conventional boiler):** The most traditional type of boiler system. It's best suited for larger properties.* **System boiler:** Stores hot water in a cylinder but has some key components built in, like the expansion vessel and pump. . It doesn't require a separate feed and expansion tank, saving some space. If you're unsure which type of boiler is best for you, consult with a Gas Safe registered heating engineer.