Solar-assisted hybrid power generation systems integrated with thermochemical fuel conversion are of increasing interest because they offer efficient use of lower temperature solar heat, with the important associated advantages of lower emissions, reduction of use of depletable fuels, production of easily storable fuel to alleviate the variability of solar heat, and relatively low cost of the use of lower temperature solar components. This paper examines economic performance of two previously proposed and analyzed thermochemical hybridized power generation systems: SOLRGT that incorporates reforming of methane, and SOLRMCC that incorporates methanol decomposition, both of which use low temperature solar heat (at similar to 220 degrees C) to help convert the methane or methanol input to syngas, which is then burned for power generation. The solar heat is used "indirectly" in the methane reforming process, to vaporize the needed water for it, while it is used directly in the methanol decomposition process since methanol decomposition requires lower temperatures than methane reforming. This analysis resulted in an equation for each power system for determining the conditions under which the hybrid systems will have a lower levelized electricity cost, and how it will change as a function of the fuel price, carbon tax rate, and the cost of the collection equipment needed for the additional heat source. (C) 2017 Elsevier Ltd. All rights reserved.