Transitioning to renewable energy systems and achieving sustainability is a complex challenge that demands extensive restructuring of systems, policies, and substantial investment. Singapore faces unique challenges in developing renewable energy resources and reducing power sector emissions due to land constraints and lack of natural resources. Consequently, about 95% of the country’s electricity generation relies on mostly imported natural gas. However, increasing solar electricity production offers a promising opportunity to diversify the energy mix. The government has set an ambitious target of achieving 2 Gigawatt-peak (GWp) of solar power capacity by 2030. The feasibility of this target is uncertain, necessitating additional incentives for growth in the land-constrained nation. The annual solar electricity yield depends on space availability for photovoltaic (PV) installations and system efficiency. Our recent studies indicate that Singapore is on track to meet the 2 GWp target by 2028, but achieving an 8% share of total electricity generation by 2040 will require policies to enhance land use efficiency, subsidies, and improved solar panel efficiency. Hence, a systems approach is necessary to study these policies and targets holistically and especially in the context of sustainably transitioning to renewable energy systems. This chapter evaluates policy recommendations for integrating solar capacity and improving energy security towards Singapore’s Green Plan targets using systems thinking and system dynamics (ST & SD) modelling approach.