Healthcare systems worldwide contribute significantly to global carbon emissions whilst facing increasing workloads from ageing populations. This creates a challenge of delivering more care while reducing environmental impact. This paper describes the development of a methodology to measure carbon efficiency in healthcare by relating carbon footprint to workload across different care settings.

The National University Health System (NUHS) in Singapore developed a workload unit (WLU) methodology to quantify carbon efficiency. Carbon footprints per unit of care were calculated across six care settings, establishing carbon relativity ratios. A polyclinic appointment was assigned one WLU, whilst an acute hospital inpatient day equated to 14.7 WLU based on relative carbon intensity. Total system workload was summated using WLUs, enabling calculation of carbon efficiency as kg CO ₂ e per WLU.

The methodology revealed improving carbon efficiency despite increasing absolute emissions from 2020-2023. Carbon per WLU decreased from 16.85 to 16.17 kg CO ₂ e, indicating effective sustainability measures. Challenges included changing emission factors and resource allocation patterns affecting carbon relativity calculations year-to-year.

This methodology enables healthcare systems to monitor environmental sustainability progress while accounting for workload changes, supporting data-driven decarbonization efforts and benchmarking between institutions delivering different care portfolios.