Laboratory efficiencies and estimated costs alone cannot assess the extent to which photovoltaics (PV) is expanding. For outdoor operation, PV technologies also need realistic yet effective methods of yield evaluation. Here, we propose an analytical approach for calculating the power output of series, parallel, and independently connected multi-junction solar cells. It uses a fast search algorithm for the maximum power point suitable for data-driven tasks. Our approach enables us to model the sub-cells of a GaInP/ GaAs/Si device, analyze its harvesting efficiency under bandgap variations, and compare tandem cell performances under different climatic conditions. Using historical, reconstructed solar spectra from 2004 to 2018 at 60 s intervals, we show the optimum tandem cell to be independent of the end user's location. We also show that independently connected junctions allow maximum flexibility in combining different materials. As such, they offer the greatest prospect of achieving harvesting efficiencies of over 40%. This study paves the way for a simpler and faster assessment of multi-junction solar cells and their performance potentials.(c) 2021 Elsevier Ltd. All rights reserved.