The introduction of SOFC-GT systems as a standard power generation system finally depends on the system’s cost. This cost is influenced by the process design and the hardware design as well. The heat exchanger cost can be influenced by a reduction of the excess air and a pressurisation of both sides of the air heater and the fuel heater. The SOFC-GT cycle with an external cooling gives the opportunity to realise these demands. The cost reduction potential of the air heater is estimated to be > 50 % compared with other SOFC-GT designs. The design of the SOFC stack itself and its integration in the pressure vessel influence the power density of the pressure vessel. The connection between stack design and pressure vessel design can be described with a simple geometric design model. It can be shown that a small tube diameter and a hexagonal spacing deliver the highest power density. The power output of the unit influences directly the consumption of the insulation material and thus of the wall material of the pressure vessel as well. This influence can be easily measured by the power related cross-section of the insulation and the wall of the vessel. Small tube diameters and a hexagonal spacing show the lowest possible material consumption and thus the lowest possible cost. It seems to be very useful to analyse the design of small SOFC tubes more deeply to reach real cost benefits.