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


  • Peter Alstone,

    Corresponding author
    • Address correspondence to: Peter Alstone, Energy and Resources Group, 310 Barrows Hall, University of California, Berkeley, Berkeley, CA 94720-3050, USA. Email:

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  • Patricia Lai,

  • Evan Mills,

  • Arne Jacobson


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 (∼20 lumens/watt [lm/W]), compared to fuel-based lighting (∼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.

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