The differences between the task of designing safe mooring systems for large floating platforms of the oil and gas offshore industry, that have severe accident consequences, and the task of designing moorings for ocean energy devices, with reduced accident consequences, are discussed. None of the existing guidelines satisfy the needs of wave energy devices. These guidelines do not consider the working principles of the devices, are too demanding as to safety or too simple and lead to expensive solutions. Wave energy devices will require a new set of design guidelines containing a new low consequence class, since mooring failure will not lead to “unacceptable consequences such as loss of life and uncontrolled outflow of oil or gas”. It should be up to the owner, insurance company and investors to balance their economic risks above a certain minimum safety level. A deeper analysis of mooring systems for ocean energy devices, compared to what is demanded for offshore oil and gas platforms, is required to properly assess the effect on the power take-off and survivability, the latter leading to economical benefits from a possible low consequence class.