Elsewhere, laboratory-scale solar cells have been demonstrated which show clear evidence of the successful exploitation of semiconducting single walled carbon nanotubes (SWNTs) as primary absorbers of sunlight energy. The unique properties of SWNTs may allow for high efficiency solar cell devices however little progress has been made to quantify this. Herein we provide an in-depth analysis of the potential of SWNTs to harvest sunlight, using the best currently available data to simulate the absorption properties of different semiconducting SWNT species and thus calculating a species-dependent potential sunlight harvesting efficiency. The same model is then used to simulate relevant tandem cell scenarios, predicting a conservative estimate of the sunlight harvesting potential of ∼28% for a multijunction device absorbing in the visible and ∼19% for a similar device absorbing primarily in the infrared, whilst minimising absorption in the visible.