- 1910: Establishment of a handicraft business by master coppersmith Emil Künzel in Guben (Niederlausitz, Germany). Pipes and production of individual items.
- End of the 20s: World financial crisis. Business taken over by engineer Paul Künzel.
- 1935: Heating stove for solid fuels with patented lift/lower grill goes to production.
- WWII, escape from Guben.
- 1950: Reestablishment of the business (PA-KÜ-Werk) in Pinneberg.
- 1955: Cooperation with Ruhrkohle AG.
- 1962: 10,000 heating stoves purchased in one year.
- 1964: Oil-fired heating stoves, steel boilers.
- 1974: Heating chest becomes most important product.
- 1975: Transfer of the company to engineers Manfred Künzel (business management) and Haiko Künzel (technical management).
- 1978/79: Oil crisis. Focus on firing techniques for solid fuels. Internal combustion system for agricultural operation, trade and commerce.
- 1985: Wood gasification boiler with patented centrifugal chamber burner.
- 1989: Microprocessor controller for wood gasification boiler.
- 1991: Biturbo wood gasifier boiler with two blowers, automatic ignition and lambda sensor for particularly exact combustion regulation.
- 2001: Pellet boiler.
- 2006: KÜNZEL wood gasifier boiler completely reworked (ceramic-free construction)
- 2007: Modular weather-actuated regulation system
- 2008: Easy-to-install hydraulic quick assembly
- 2009: Pelletboiler PK