Nate Hagens defines 'energy surplus' as the critical measure of available energy that exceeds the amount required to sustain fundamental activities within a system. This surplus is what allows complex systems, such as human societies, to grow, prosper, and develop intricate cultural, technological, and economic frameworks. He emphasizes that the concept extends beyond mere caloric or fossil fuel inputs, encompassing all forms of energy that contribute to and enhance the functionality of a system. Hagens underscores the importance of energy surpluses in enabling innovation, infrastructure development, and socio-economic advancement, while also highlighting the potential ecological and sustainability challenges linked to the management and distribution of these surpluses.

See also: renewable energy, fossil energy, nuclear power, electric car