**6. Conclusions**

This study presents an interdisciplinary approach to evaluate the sustainability of RE mini-grids in SSA incorporating the technical, financial and communal dimensions. A comprehensive literature review, community survey data from Uganda and Zambia as well as the in-depth evaluation of two MG case studies from Zambia reveals the interdependency of financial—technical—and social sustainability.

The study has shown that an off-grid system is operationally sustainable if it can provide affordable energy access and deliver the desired outcomes over its estimated lifespan and that these interdependencies, however, exist partially in tension with each other. Social sustainability which includes affordable tariffs, for example, can bear tradeoffs for example with financial sustainability in terms of recovering MG development—and operation costs. Consequently, sustainable off-grid electrification in sub-Saharan Africa requires an approach that goes beyond a top-down planning process that is solely focused on the provision of electricity.

Actual community energy needs and demands as well as the socio-economic structure are critical components for the long-term sustainability of energy systems and must be taken into account when an MG is going to be developed and implemented.

The interdisciplinary study allows five general conclusions with regard to the implementation of RE MGs in developing contexts:

Current MG energy tariffs are often ye<sup>t</sup> far beyond local affordability levels which is also related to the requirement of tariff cost-reflectiveness in most SSA countries, high equipment costs and oversized systems. Consequently, local affordability levels should function as a key baseline for MG-planning- as well as wider electrification processes and design the systems based on local income and energy demand levels. This approach also includes close monitoring and benchmarking of system costs (CAPEX), especially if projects are donor-funded, the realistic sizing of the system as well as the acknowledgement of key community challenges that trigger low and intermittent incomes. These considerations also open the general debate whether it is realistic to achieve national energy access goals for low-income, rural areas until 2030 through the application of cost-reflective tariff schemes or whether rural energy consumption can only be triggered through mid- to longer-term energy tariff subsidies.

The complex challenges for rural African communities that are dependent on smallscale farming or fishing undermine the longer-term financial sustainability of MGs and are likely to be exacerbated by the effects of climate change. In addition to that, limited access to productive appliances, a of local know-how, decency on seasonal rainfalls and a lack of local capital often restrict rural communities from the uptake of the energy provided through off-grid systems.

Integrated planning approaches that flank energy system development and which focus on overcoming these specific challenges, for example through providing irrigation, training or access to appliances including financing schemes. Consequently, this paper calls for a change of the energy-access narrative from the focus of systems deployed or connections provided to the consideration of energy as a tool to support rural socioeconomic development through the creation of added value and as one infrastructure component to be implemented alongside bundled measures that target key challenges for rural communities. The access to affordable and good quality appliances for private or commercial use in rural areas is still a major challenge and the establishment of affordable

supply—and maintenance systems in the appliance sector are thus key to the utilisation of energy.

From a policy level, the findings sugges<sup>t</sup> the promotion of feasibility studies that realistically benchmark local income—and projected energy tariff levels during the project planning and -application stage, support mechanisms for enhanced community engagement beyond the sole local approval of energy projects and the promotion of integrated infrastructure solutions. Projects publicly funded by donors or local governmen<sup>t</sup> need to be closely evaluated in terms of CAPEX and prospected CAPEX in terms of realistic market pricing.

The scaling of sustainable RE mini-grids requires innovative financing approaches that go beyond pure upfront CAPEX grant-financing. Infrastructure solutions in rural settings of developing countries must be considered in the context of their operational environment, the community ecosystem which determines the sustainability of these solutions. The current trend of implementing largely gran<sup>t</sup> financed, CAPEX intensive solutions with very limited community involvement does neither incentivize the productive use of energy through lower tariffs nor facilitate long-term sustainability and operation of these systems. The clustering of mini-grids can help in lowering down CAPEX and OPEX which can create a positive impact on energy tariffs and consumption. The provision of electricity is only one element of mini-grid planning and need to be aligned with energy uptake and added-value generating productive use of energy. Results-based financing approaches and carbon-credit financing that focus on longer-term mini-grid operation and energy uptake can be a key element of future financing approaches with this regard but require further research in terms of practical applicability.

The scaling of sustainable off-grid energy systems also requires adequate regulatory frameworks that technical quality, frictionless project implementation, strategic energy planning scenarios that integrate the on-and off-grid sectors flanked by investigating future grid-distribution strategies.

The danger of creating 'White Elephants' at scale, gran<sup>t</sup> financed projects that are unsustainable and will be abandoned if operation costs permanently exceed revenues, is very real. The \$1.3 million Mpanta mini-grid, which was commissioned in 2013, is currently on the brink of being decommissioned as the national electrical grid is now just about two km away from the village and due to replace the mini-grid very soon. According to REA Zambia, the solar PV mini-grid will be decommissioned. Batteries will be sold to a recycling plant. There are currently no plans available for utilising other assets of the mini-grid.

**Author Contributions:** S.S.: Conceptualization, methodology, validation, formal analysis, investigation, resources, data curation, writing—original draft preparation, writing—review and editing, visualization, project administration, funding acquisition. P.J.: formal analysis, investigation, data curation, writing—review and editing. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Global Challenges Research Fund (GCRF) and the Economic and Socual Research Council (ESRC) and the product of the research projects 'RISE' (https: //www.smithschool.ox.ac.uk/research/rise-renewable-energy-innovation-scale/) and Mumuni Singani (https://www.smithschool.ox.ac.uk/research/mumuni-singani/index.html).

**Data Availability Statement:** Data supporting reported results can be found under https://www. smithschool.ox.ac.uk/research/mumuni-singani/index.html (accessed on 8 June 2021).

**Acknowledgments:** The authors are grateful for the cooperation and the provision of data by the Department of Physics of the University of Zambia (UNZA), Youth Development Organisation Zambia (YDO), Muhanya Solar Ltd. Zambia, the Rural Electrification Authority Zambia as well as for the technical guidance provided by Juergen Doering (NDL Renewables). The authors gratefully acknowledge the support of Chilangisha Changwe (Department of Physics, UNZA), Tonny Kukeera (University of Oxford) for content support and Aoife B. Haney (University of Oxford) who supported the project as Principal Investigator (https://www.smithschool.ox.ac.uk/research/mumuni-singani/ people.html, accessed on 21 June 2021). The authors also thank the team of project 'RISE' (https: //www.smithschool.ox.ac.uk/research/rise-renewable-energy-innovation-scale/, accessed on 8 June 2021) and their partners who were involved in part of the community data collection for Uganda and Zambia.

**Conflicts of Interest:** The authors declare no conflict of interest.
