A steam boiler is a device used to create steam by applying heat energy to water. Although the definitions are somewhat flexible, it can be said that older steam generators were commonly termed steam boiler and worked at low to medium pressure (1–300 psi or 6.895–2,068.427 kPa) but, at pressures above this, it is more usual to speak of a steam generator.

Steam boilers offer a number of benefits, including:

• High efficiency
• Low maintenance
• Long lifespan
• Versatility