Sustainability guardrails in global energy scenarios were reviewed and further developed based on a literature review of global energy system transition scenarios. Environmental planetary boundaries mark out the safe operation space for human activities. The planetary boundary framework has yet to be fully incorporated into global energy scenario modeling, where the emphasis has been almost solely on CO 2 emission mitigation. Stress on biochemical flows, land use change, biodiversity, ocean and climate systems are often neglected. Concurrently, social and economic aspects, such as limiting air pollution, providing universal access to modern energy services and improving energy efficiency by electrification of energy services are emerging as new paradigms in energy scenario modeling frameworks. However, ethical choices, such as current and future generations’ access to preserved ecosystems, aversion of energy resource risks, preventing resource use conflicts, and negative impacts on human lives from energy extraction and use are not usually discussed or justified in energy scenario modeling. All investigated global energy transition scenarios failed to adequately describing the critical roles of flexibility in future energy systems based on high shares of renewable energy, such as storage, grids, demand response, supply side management and sector coupling. Nor did they adequately incorporate the concept of resilience in socio-ecological systems.