Climate change makes it necessary to switch from fossil fuels to sustainable energy sources. Combined heat and power (CHP) plants, which are attractive for decentralized energy supply, can be converted from natural gas to hydrogen. This article examines three components from the CHP plant: cylinder liners, exhaust manifolds, and cylinder heads. Concepts for increasing efficiency through additive manufacturing are presented, taking into account the design goals and manufacturing restrictions of additive manufacturing. Cooling channels up to 4 m long are incorporated into the liners to enable targeted temperature control in different areas. The newly developed exhaust manifold could direct the exhaust gas from the cylinder head to the turbocharger with constant inflow and is completely surrounded by cooling water to prevent heat loss. Additively manufactured inlays on the cylinder head demonstrate the feasibility of incorporating surface-close cooling channels for particularly hot areas.