4.3.1. Complexity Factor

Complexity describes the di fficulty one might encounter when adopting an EEM, inversely proportional to the adoption rate of the measure itself [99]. Understanding in which cases the adoption is revealed to be complex is a fundamental passage to characterize it. Literature on innovation refers to the radicalness as an index of complexity, since it is correlated to the degree of change required for the adopters [122]. This is a rather vague definition for the specific study and a potential source of misunderstanding [26,123]. Hence, we decomposed the complexity into factors whose definitions are specifically intended for the analysis of EEMs.

*Activity type* distinguishes if an EEM constitutes a simple refurbishment or recovery of the existing functions, an optimization in the use of an existing technology, a retrofitting of the equipment or a new energy-e fficient equipment installation [7]. Indeed, a simple retrofit is easier than a new investment in equipment [124].

*Expertise required* refers to the range of skills required for the correct implementation of an EEM. Since di fferent levels of expertise are required for each EEM and considering their variety, the skill range can be wide enough to be hard for firms in finding technology experts, especially for SMEs, where CAS is used almost exclusively as a service [125].

*Independency from other components*/*EEMs* refers to the influence of the implementation of an EEM on the existing system, to underline the nature of the impact [26,100,126]. The possible impacts can influence CAS equipment working conditions, other systems or can generate cause–e ffect relationships with other EEMs, with the magnitude of the influence being inversely proportional to the easiness of understanding the consequences of the installation and predicting the total savings.

*Change in maintenance <sup>e</sup>*ff*ort*. The variation of maintenance requirements as a consequence of the adoption of EEMs has been often considered an important factor by previous literature [102,105,106].

*Accessibility*. Di fficulties in accessing equipment may require higher e fforts from personnel or a greater amount of technological resources to carry out operations; this can be even harder for CAS, in which the distribution system is usually di fficult to access. Moreover, accessibility may also refer to space unavailability for maintenance procedures when technology add-on measures are installed.
