Mini-Grid Sizing

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Mini-Grid Sizing Guidebook.pdf

This handbook has been developed as part of a series of handbooks on minigrids. After the publication of handbooks on site selection (“Where shall we put it?”) and licensing (“How do we license it?”) this handbook on load assessment and mini-grid system sizing is the third publication in the series. While the first two handbooks focused on the Kenyan context, this handbook is applicable to all the various geographical contexts where mini-grids can be implemented. Practical knowledge has been drawn from the authors’ experience in mini-grid implementation in sub-Saharan Africa.

Most of the content of this handbook has general validity for load assessment and system sizing. However, the methodology for the actual sizing (Chapter 2) is based on the approach of the mini-grid builder, an online tool developed by GIZ ProSolar in 2015, based on the experiences made with load assessment and system sizing of a pilot solar-hybrid mini-grid in Talek, Narok County (Kenya). It should be noted that this is just one viable approach for system sizing, some others being mentioned in Chapter 3. 

Adequate load assessment and demand forecast, as well as subsequent system sizing, is essential for the appropriate design of mini-grids. The economic viability of mini-grid projects depends on the size of the installed assets — and thus the investments — which need to be backed by a payable demand in the years after commissioning. A wrongly configured system (too small or too large) will either not serve its purpose or not recover the costs required to set it up. We thus deem it highly important to discuss demand assessment and mini-grid sizing in this handbook. 

As it is easier to determine the size for capacity additions to existing schemes (e.g. hybridisation of existing diesel mini-grids with solar), this handbook focuses on the more challenging case of load assessment and sizing for new mini-grids in areas without electricity. Such ‘greenfield’ sites represent the larger share in terms of rural electrification opportunities. Furthermore, as solar-hybrid minigrids are often the most viable set-up in the sub-Saharan context, the main focus of this handbook is on these systems.

While this handbook intends to display the required knowledge for systems sizing and demand forecast, mini-grid projects are very site specific. The authors of this handbook therefore do not accept any liability for commercial or investment decisions taken on the grounds of the knowledge presented within. It is recommended to always conduct a proper due diligence and closely collaborate with an expert to configure mini-grid systems appropriately.

Webinar on system design of off-grid systems:

Table of Contents 

Link of the guidebook: Mini-Grid Sizing Guidebook

  1. Introduction 13

             1.1. Prospects for rural electrification 13
             1.2. Mini-grids and the relevance of accurate system sizing 15

         2. Sizing a mini-grid 20

             2.1. Initial project assessment 22
             2.2. Assessment of present electricity demand 23
             2.3. Effective electricity demand and its calculations 28
             2.4. Forecasting effective demand 32
             2.5. System sizing and design 36
        3. Tools for system sizing 43
             3.1 Overview of existing tools for system sizing 43
             3.2. Description of mini-grid builder 45
             3.3. Description of HOMER Energy 46
        4. Conclusion 50
        5. Annex 51
             5.1. Required information for load assessment and system sizing 53
             5.2. Mini-grid builder 54
        Bibliography 66

Further Information

This guidebook has been developed as part of a series of handbooks on mini-grids. You can check out the other ones in the following webpages:


  • Fricke, D. (2015): “Qinous Energy Solutions: PV Hybrid in Off-Grid and Mini-Grid solutions”. Presentation given in Manila, October 2015.
  • GIZ (2015): Mini-grid builder: Web-Based Mini-Grid Tool. Available from [accessed 21 June 2016] 
  • HOMER (2016): Homer Energy Support Knowledgebase. [Accessed: 17th June 2016]
  • IEA (2015): World Energy Outlook 2015. International Energy Agency, Paris, France. Available from [accessed: 17 December 2015] 
  • IEA (2014): Africa Energy Outlook 2014. International Energy Agency, Paris, France. Available from [accessed 15 June 2016]
  • IEA (2013): Rural Electrification with PV Hybrid Systems. International Energy Agency, Paris, France. ISBN: 978-3-906042-11-4 IEA and World Bank (2015): Sustainable Energy for All 2015—Progress Toward Sustainable Energy 2015. World Bank, Washington, DC. Available from [accessed 15 June 2016]
  • IRENA (2015): IRENA Off-grid Renewable Energy Systems: Status and methodological issues. International Renewable Energy Agency (IRENA) Innovation and Technology Centre, Bonn, Germany
  • NRECA (2011): Guides for Electric Cooperative Development and Rural Electrification, NRECA International,
  • RECP (2014): Mini grid policy toolkit. European Union Energy Initiative Partnership Dialogue Facility (EUEI PDF), Eschborn, Germany 
  • SDGH (2014): Solar/Diesel Mini-Grid Handbook. Power and Water Corporation (PWC), Darwin, Australia 
  • World Bank (2016): Current Activities and Challenges to Scaling up Mini-Grids in Kenya. Energy Sector Management Assistance Program (ESMAP). World Bank, Washington, DC.