We examine whether giving individuals an active choice to participate in an energy conservation program strengthens engagement. We hypothesize that voluntary adoption of energy-saving goals may lead to stronger outcomes than assigned goals, partly because making an active choice increases psychological ownership and attention. To test this, we ran a field experiment with 1,642 Taiwanese households, randomly assigned to a control group, an Assigned Goal treatment, or an Adopted Goal treatment where participants could opt in. The experiment had two phases: Phase 1 included only incentivized energy-saving goals; Phase 2 added energy-saving tips and task-based incentives. Goals alone did not significantly reduce electricity use. Once task-based incentives were added, significant savings emerged—but only for those who voluntarily adopted the goal. They were also more likely to complete the tasks, indicating that voluntary commitment and attention supported sustained engagement. The findings highlight the value of active choice in improving the cost-effectiveness of conservation programs.