Fusion plants are expected to use molten salts to transfer heat which sounds like it can allow up to 55% conversion efficiency (vs as low as 30% for light water fission)

Molten salts come with engineering headaches but it also makes fusion a more convenient source of process heat for industry. A study on the ARC design, that is looking to have its physics validated in 2026 by the SPARC machine, found it could produce CO2 free ammonia for shipping fuel at little more cost than current methods by using its electricity and heat

also, when it comes to finding fusion steam engines boring, sometimes I fear the wrath of Isaac Newton when someone brings him from the past to show him our literally alchemy powered fission and fusion plants producing electricity in quantities more valuable than the worldwide gold trade