High Life Cycle Efficacy Explains Fast Energy Payback for Improved Off-Grid Lighting Systems

The energy intensity of fuel-based lighting is substantial given the paltry levels of lighting service, poor economic outcomes, and exposure to public health risks for users throughout the developing world. There is a great opportunity to reduce fossil energy consumption (and mitigate greenhouse gas emissions) while improving public health and economic outcomes for the poor by encouraging upgrading from fuel-based to rechargeable light-emitting diode (LED) lighting. However, switching to efficient lighting requires up-front investments of energy for manufacturing. This study explores life cycle energy performance in the market for modern off-grid lighting (OGL) products in Sub-Saharan Africa and introduces a new metric, life cycle efficacy, which facilitates comparisons and analysis of life cycle energy performance (light output per unit of embodied plus use-phase energy consumption) for lighting technology systems. Combining field insights on technology adoption dynamics with embodied energy estimates for a range of products available in 2012 shows that OGL energy "debts" are "paid back" in 20 to 50 days (substantially faster than kilowatt-scale grid-connected solar electricity systems) with energy return on investment ratios from 10 to 40. This stems from greatly improved life cycle efficacy for off-grid LED lighting (similar to 20 lumens/watt [lm/W]), compared to fuel-based lighting (similar to 0.04 lumens/W). Life cycle benefits-not only energy, but also economic and health benefits-depend strongly on product service lifetime (related to quality) and fuel displacement fraction (related to performance). OGL life cycle efficacy increases from longer lifetime and/or improved LED source efficacy lead to better quality and less-expensive lighting available in the developing world with lower energy use than the fuel-based incumbent technology.