The cost of reliability in decentralized solar power systems in sub-Saharan Africa


Although there is consensus that both grid extensions and decentralized projects are necessary to approach universal electricity access, existing electrification planning models that assess the costs of decentralized solar energy systems do not include metrics of reliability or quantify the impact of reliability on costs. We focus on stand-alone household solar systems with battery storage in sub-Saharan Africa using the fraction of demand served to measure reliability, and develop a multistep optimization to compute efficiently the least-cost system with the fraction of demand served as a design constraint, and take into account the daily variation in solar resources and costs of solar and storage. We show that the cost of energy is minimized at approximately a 90% fraction of demand served, that current costs increase, on average, by US$0.11 kWh–1 for each additional ‘9’ of reliability, and that this reliability premium could be as low as US$0.03 kWh–1 in a plausible future price scenario.

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Fig. 1: ASAI for countries in SSA.
Fig. 2: LCOE of Tier 5 decentralized systems in the present and future scenarios.
Fig. 3: Statistical relationship of LCOE and FDS in SSA.
Fig. 4: Spatial distribution of reliability premium.
Fig. 5: Predictive power of mean insolation on the LCOE.
Fig. 6: Cost difference between decentralized solar LCOE and grid tariffs.

Data availability

All of the data used in this study, with the exception of the sample microgrid load profile from Uganda, is publicly available and referenced here. The sample microgrid load profile is owned by New Sun Road, P.B.C., and can be made available upon reasonable request. Tables on national electrification rates35, grid reliability28 and electricity tariffs34 used to generate Figs. 1 and 6 are included in Supplementary Table 1 for convenience. Solar insolation data are available from the US National Aeronautics and Space Administration38, and the code to download and analyse this data is available at the repositories listed above.


  1. 1.

    Transforming Our World: the 2030 Agenda for Sustainable Development (UN General Assembly, 2015).

  2. 2.

    Sustainable Energy for All 2017 - Progress toward Sustainable Energy (International Energy Agency and The World Bank, 2017);

  3. 3.

    Alstone, P., Gershenson, D. & Kammen, D. M. Decentralized energy systems for clean electricity access. Nat. Clim. Chang. 5, 305–314 (2015).

    Article  Google Scholar 

  4. 4.

    Renewables 2017 Global Status Report (REN21, 2017);

  5. 5.

    Cader, C., Bertheau, P., Blechinger, P., Huyskens, H. & Breyer, C. Global cost advantages of autonomous solar–battery–diesel systems compared to diesel-only systems. Energy Sustain. Dev. 31, 14–23 (2016).

    Article  Google Scholar 

  6. 6.

    Szabó, S., Bódis, K., Huld, T. & Moner-Girona, M. Energy solutions in rural Africa: mapping electrification costs of distributed solar and diesel generation versus grid extension. Environ. Res. Lett. 6, 034002 (2011).

    Article  Google Scholar 

  7. 7.

    Breyer, C. et al. On the role of solar photovoltaics in global energy transition scenarios. Prog. Photovoltaics Res. Appl. 25, 727–745 (2017).

    Article  Google Scholar 

  8. 8.

    Bertheau, P., Oyewo, A., Cader, C., Breyer, C. & Blechinger, P. Visualizing national electrification scenarios for sub-Saharan African countries. Energies 10, 1899 (2017).

    Article  Google Scholar 

  9. 9.

    Lee, K. et al. Electrification for ‘under grid’ households in rural Kenya. Dev. Eng. 1, 26–35 (2016).

    Article  Google Scholar 

  10. 10.

    McKibben, B. The race to solar power Africa The New Yorker (26 June 2017).

  11. 11.

    World Energy Outlook 2016 (International Energy Agency, 2016);

  12. 12.

    Miketa, A. & Saadi, N. Africa Power Sector: Planning and Prospects for Renewable Energy (International Renewable Energy Agency, 2015);

  13. 13.

    Miketa, A. & Merven, B. Southern African Power Pool: Planning and Prospects for Renewable Energy (International Renewable Energy Agency, 2013);

  14. 14.

    Miketa, A. & Merven, B. West African Power Pool: Planning and Prospects for Renewable Energy (International Renewable Energy Agency, 2013);

  15. 15.

    Wu, G. C., Deshmukh, R., Ndhlukula, K., Radojici, T. & Reilly, J. Renewable Energy Zones for the Africa Clean Energy Corridor (International Renewable Energy Agency, 2015);

  16. 16.

    Levin, T. & Thomas, V. M. Least-cost network evaluation of centralized and decentralized contributions to global electrification. Energy Policy 41, 286–302 (2012).

    Article  Google Scholar 

  17. 17.

    Levin, T. & Thomas, V. M. Can developing countries leapfrog the centralized electrification paradigm? Energy Sustain. Dev. 31, 97–107 (2016).

    Article  Google Scholar 

  18. 18.

    Parshall, L., Pillai, D., Mohan, S., Sanoh, A. & Modi, V. National electricity planning in settings with low pre-existing grid coverage: development of a spatial model and case study of Kenya. Energy Policy 37, 2395–2410 (2009).

    Article  Google Scholar 

  19. 19.

    Kemausuor, F., Adkins, E., Adu-Poku, I., Brew-Hammond, A. & Modi, V. Electrification planning using Network Planner tool: the case of Ghana. Energy Sustain. Dev. 19, 92–101 (2014).

    Article  Google Scholar 

  20. 20.

    Szabó, S., Bódis, K., Huld, T. & Moner-Girona, M. Sustainable energy planning: leapfrogging the energy poverty gap in Africa. Renew. Sustain. Energy Rev. 28, 500–509 (2013).

    Article  Google Scholar 

  21. 21.

    Cader, C., Blechinger, P. & Bertheau, P. Electrification planning with focus on hybrid mini-grids—a comprehensive modelling approach for the global South. Energy Proced. 99, 269–276 (2016).

    Article  Google Scholar 

  22. 22.

    Lee, M., Soto, D. & Modi, V. Cost versus reliability sizing strategy for isolated photovoltaic micro-grids in the developing world. Renew. Energy 69, 16–24 (2014).

    Article  Google Scholar 

  23. 23.

    Deichmann, U., Meisner, C., Murray, S. & Wheeler, D. The economics of renewable energy expansion in rural Sub-Saharan Africa. Energy Policy 39, 215–227 (2011).

    Article  Google Scholar 

  24. 24.

    Nyakudya, R., Mhlanga, S., Chikowore, T. R. & Nyanga, L. in 2013 IEEE International Conference on Industrial Technology 1443–1449 (IEEE, 2013);

  25. 25.

    Szabó, S., Moner-Girona, M., Kougias, I., Bailis, R. & Bódis, K. Identification of advantageous electricity generation options in sub-Saharan Africa integrating existing resources. Nat. Energy 1, 16140 (2016).

    Article  Google Scholar 

  26. 26.

    Zeyringer, M. et al. Analyzing grid extension and stand-alone photovoltaic systems for the cost-effective electrification of Kenya. Energy Sustain. Dev. 25, 75–86 (2015).

    Article  Google Scholar 

  27. 27.

    Billinton, R. & Allan, R. N. in Handbook of Reliability Engineering (ed. Pham, H.) 511–528 (Springer-Verlag, Heidelberg, 2003).

  28. 28.

    Enterprise Surveys (The World Bank, 2017);

  29. 29.

    Ferrall, I. Measuring electricity reliability of decentralized solar energy systems. C3E Women in Clean Energy Symposium (2017).

  30. 30.

    Bhatia, M. & Angelou, N. Beyond Connections: Energy Access Redefined Technical Report 008/15 (The World Bank, 2015).

  31. 31.

    Bucciarelli, L. L. Estimating loss-of-power probabilities of stand-alone photovoltaic solar energy systems. Sol. Energy 32, 205–209 (1984).

    Article  Google Scholar 

  32. 32.

    Annual Electric Power Industry Report (US Energy Information Administration, 2015);

  33. 33.

    Taneja, J. Measuring Electricity Reliability in Kenya (2017).

  34. 34.

    Trimble, C., Kojima, M., Perez-Arroyo, I. & Mohammadzadeh, F. Financial Viability of Electricity Sectors in sub-Saharan Africa. Quasi-fiscal Deficits and Hidden Costs Policy Research Working Paper 7788 (The World Bank, 2016);

  35. 35.

    Access to Electricity (% of Population) (The World Bank, accessed 8 November 2017);

  36. 36.

    Solar PV in Africa: Costs and Markets (International Renewable Energy Agency, 2016);

  37. 37.

    Burlig, F. & Preonas, L. Out of the Darkness and Into the Light? Development Effects of Rural Electrification

  38. 38.

    Surface Meteorology and Solar Energy (US National Aeronautics and Space Administration, accessed 19 April 2018);

  39. 39.

    Duffie, J. A. & Beckman, W. A. Solar Engineering of Thermal Processes 4th edn (Wiley, Hoboken, 2013).

    Google Scholar 

  40. 40.

    Leadbetter, J. & Swan, L. G. Selection of battery technology to support grid-integrated renewable electricity. J. Power Sources 216, 376–386 (2012).

    Article  Google Scholar 

  41. 41.

    Dunn, B., Kamath, H. & Tarascon, J.-M. Electrical energy storage for the grid: a battery of choices. Science 334, 928–935 (2011).

    Article  Google Scholar 

  42. 42.

    Divya, K. C. & Østergaard, J. Battery energy storage technology for power systems—an overview. Electr. Power Syst. Res. 79, 511–520 (2009).

    Article  Google Scholar 

  43. 43.

    Diouf, B. & Pode, R. Potential of lithium-ion batteries in renewable energy. Renew. Energy 76, 375–380 (2015).

    Article  Google Scholar 

  44. 44.

    Albright, G., Edie, J. & Al-Hallaj, S. A Comparison of Lead Acid to Lithium-ion in Stationary Storage Applications (AllCell Technologies, Chicago, 2012);

  45. 45.

    Chattopadhyay, D., Bazilian, M. & Lilienthal, P. More power, less cost: transitioning up the solar energy ladder from home systems to mini-grids. Electr. J. 28, 41–50 (2015).

    Google Scholar 

  46. 46.

    Baurzhan, S. & Jenkins, G. P. Off-grid solar PV: is it an affordable or appropriate solution for rural electrification in Sub-Saharan African countries? Renew. Sustain. Energy Rev. 60, 1405–1418 (2016).

    Article  Google Scholar 

  47. 47.

    Cole, W. J., Marcy, C., Krishnan, V. K. & Margolis, R. in 2016 North American Power Symposium 1–6 (IEEE, 2016);

  48. 48.

    The Power to Change: Solar and Wind Cost Reduction Potential to 2025 (International Renewable Energy Agency, 2016);

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We thank the US National Science Foundation for supporting this work through the CyberSEES program (award no. 1539585) and are grateful to J. P. Carvallo, R. Shirley, D. Kammen and I. Ferrall for their advice and comments. We also thank J. Sager and New Sun Road, P.B.C., for sharing their insights into decentralized system designs and sample data from their systems.

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J.T.L. contributed the primary development of the optimization program, methods and computer modelling. D.S.C. supervised the research effort. The authors jointly developed the research questions, analysis, conclusions and manuscript.

Corresponding author

Correspondence to Duncan S. Callaway.

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Supplementary Information

Supplementary Notes 1–4, Supplementary Figures 1–5, Supplementary Tables 1–4, Supplementary References

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Lee, J.T., Callaway, D.S. The cost of reliability in decentralized solar power systems in sub-Saharan Africa. Nat Energy 3, 960–968 (2018).

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