The building and construction sector is a significant global energy consumer and a major contributor to CO2 emissions. This high energy consumption is heavily influenced by occupant behaviours within buildings. Existing literature has emphasised the need to adopt a holistic approach, incorporating indoor environmental quality (IEQ) parameters (i.e., thermal, indoor air quality, visual, acoustic) and social-psychological factors (i.e., attitudes, norms, perceived behavioural control, knowledge), rather than relying solely on objective models. This chapter is dedicated to creating an innovative tool known as the Occupant Energy Behaviour Tool, primarily focusing on its application in New Zealand. The findings presented in this chapter were based on research methodology that comprises two main components: (1) a comprehensive review of existing literature, aiming to identify prevalent occupant energy behaviours and the multifaceted drivers that shape them, both within New Zealand and on a global scale, and (2) a quantitative approach that investigates the perceptions of 393 office building occupants regarding their decision-making processes related to energy behaviour. The sample was chosen through stratified random sampling to represent diverse environments across New Zealand. The analysis includes Partial Least Squares Structural Equation Modelling (PLS-SEM) and decision tree analysis to interpret occupants’ energy behaviours. The developed tool offers a comprehensive framework for monitoring and collecting data on occupant energy behaviours. It is vital for analysing and improving energy behaviours in New Zealand’s office buildings adapting to local needs and applying broadly, enhancing energy efficiency and sustainability. This tool integrates occupant behaviours into energy strategies and simulations, significantly boosting building performance.