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The multi-generation systems with simultaneous production of power by renewable energy, in addition to polymer electrolyte membrane electrolyzer and fuel cell (PEMFC-PEMEC) energy storage, have become more and more popular over the past few years. The fresh water provision for PEMECs in such systems is taken into account as one of the main challenges for them, where conventional desalination technologies such as reverse osmosis (RO) and mechanical vapor compression (MVC) impose high electricity consumption and costs. Taking this point into consideration, as a novelty, solar still (ST) desalination is applied as an alternative to RO and MVC for better techno-economic justifiability. The comparison, made for a residential building complex in Hawaii in the US as the case study demonstrated much higher technical and economic benefits when using ST compared with both MVC and RO. The photovoltaic (PV) installed capacity decreased by 11.6 and 7.3 kW compared with MVC and RO, while the size of the electrolyzer declined by 9.44 and 6.13%, and the hydrogen storage tank became 522.1 and 319.3 m3 smaller, respectively. Thanks to the considerable drop in the purchase price of components, the payback period (PBP) dropped by 3.109 years compared with MVC and 2.801 years compared with RO, which is significant. Moreover, the conducted parametric study implied the high technical and economic viability of the system with ST for a wide range of building loads, including high values.

Due to much lower initial and operating costs, as well as a great environmental and energy performance, there has been a growing tendency towards the application of solar still desalination systems to deal with water scarcity issues. By taking advantage of higher investments and providing incentives to policy makers, the application could be even broader. In order to convince the policy makers and investors, it is important to provide a clear and realistic overview of the technical, economic, and environmental viability of solar stills, and several studies have evaluated them from different viewpoints. Nonetheless, the economic and environmental factors have uncertainties, which have not been taken into account. Therefore, this study uses the Monte Carlo approach to consider the effects of the uncertainty of inflation and discount rates, in addition to emission factors, on the system’s techno-enviro-economic viability. The study is performed by covering cost per liter (CPL) and the annual saving of CO2 (SCO2) as the most important key techno-economic and environmental indicators of the system. The results show that the best probability distribution functions for inflation, discount, and emission factors are normal, log-normal, and their summation, respectively. Furthermore, both SCO2 and CPL are found to have considerable uncertainty. The former has a variation ranging from 317.7 to 427.9 g, while the corresponding values for the latter are 0.0212 to 0.0270 $ · L−1, respectively. With the amounts of 0.1716 and 0.1727, the values of 378.9 g and 0.0245 $ · L−1 are the values with the highest chance of occurrence for SCO2, as well as for CPL, respectively.