Conventional Darrieus vertical-axis wind turbines exhibit relatively high aerodynamic efficiency but suffer from poor self-starting capability at low wind speeds.

Caveats

• The self-starting limitation is well-documented for conventional Darrieus designs but can be mitigated through hybrid configurations (e.g., Darrieus–Savonius), helical blades, variable pitch, or auxiliary starting mechanisms.
• "Relatively high aerodynamic efficiency" is measured against other VAWT types (especially drag-based Savonius); Darrieus turbines generally remain less efficient than modern horizontal-axis wind turbines.
• Performance characteristics depend on specific conditions including Reynolds number, solidity, airfoil choice, and turbulence intensity — the claim is a valid generalization, not an absolute rule.