New and comprehensive time-accurate, experimental data from an H-Darrieus wind turbine are presented to further develop our understanding of the performance of these turbines with a particular focus on self-starting. The impact of turbine solidity, blade profile, surface roughness, pitch angle, and aspect ratio on the turbine's performance is investigated, parameters that are thought to be critical for small-scale VAWT operation, particularly when operating in the built environment. It is demonstrated clearly that high turbine solidity (Formula presented.) is beneficial for turbine self-starting and that the selection of a thick, symmetrical aerofoil set at a low, negative pitch angle ((Formula presented.)) is better than a cambered foil. Increased blade surface roughness is also shown to improve a turbine's self-starting capability at low tip speed ratios and with high turbine solidity and the associated flow physics are discussed. Finally, it was confirmed that blade span has a significant impact on turbine starting. This paper contributes to the understanding of the turbine characteristics during the starting period and provides clear guidance and validation cases for future design and research in order to promote and justify the wider application of this wind turbine configuration.