To achieve cost parity with other renewables, the wave energy sector requires significant cost reduction. Increasing the wind turbine scale is one successful route to cost reduction in the wind industry. This paper aims at investigating the scalability of wave energy converters (WECs) and providing a thorough review and analysis of published data. Unlike wind turbines for which the energy absorbed increases with turbine diameter, the scalability of WECs is complicated and varies by WEC type. Here, we demonstrate that the point absorber (PA) WEC lacks scalability and has limited theoretical capture width (CW), although its theoretical capture width ratio (CWR) can exceed 100%. The CW increases with device width for terminator and length for attenuator WECs, demonstrating scalability, but CWR limits of 50% and 100% exist. Analysis of the practical performance data carried out in this work shows that: (1) due to the lack of scalability, it will be difficult for the PA unit to reach MW scale, and in most examples, the characteristic dimension is generally < 35 m; (2) the terminator could achieve MW scale by using a high characteristic dimension > 100 m; (3) the PA appears to work more efficiently than the terminator and attenuator (e.g., for the PA oscillating wave surge converters, hydrodynamic efficiencies up to 80% have been achieved in laboratory tests).