Providing remote and off-grid coastal communities with renewable and sustainable electricity is a goal that could be met with tidal-stream technology. Presently there are many turbine designs, which presents a challenge when making an unbiased resource assessment. Moreover, the majority of tidal-stream turbines appear to be aimed at producing large amounts (i.e. GigaWatt scales) of electricity, for national transmission networks, from very fast tidal current sites (because power is proportional to velocity cubed). Analysis of 14 horizontal axis tidal-stream turbine designs allowed the behaviour of a standardized, normalised power-density curve to be parameterized. An optimal power-density curve was then assessed for every site up to 25km from a coastline using global tide data (FES2014) due to the deterministic characterisation of resource with harmonics. Based on the algorithm weighting for an optimal power-density curve, a strong linearrelationship between tidal current climatology and choice of optimal performance was found: Maximum yield had a rated speed ~97% of maximum tidal-current speed (maxU); “High yield” scenario (highest Capacity Factor in top 5% highest-yield cases) had turbine rated speed of ~87% of maxU. An optimal turbine rated speed of ~56% of maxU was found when selecting the optimal power-density curve for firm power (highest Capacity Factor with no gap in power supply greater than 2 hours), which may be important if energy storage is problematic or expensive. Further, we find optimisation and convergent design based on resource is possible, and our standardised power curve should help future research in resource and environmental impact assessment.