Regional coordination can alleviate the cost burden of a low-carbon electricity system.

Long-term planning of low-carbon electricity systems in the Global South involves deeply uncertain infrastructure investments, often undertaken independently from neighboring energy systems. In principle, national grids benefit from greater regional integration, but the nature of these benefits is sensitive to techno-economic uncertainty and natural resource distribution. We examine the value of regional electricity coordination for a South American subregion with abundant, geographically variable renewable resources, under stringent emissions reduction targets and a range of techno-economic assumptions. Results show that decarbonization is achievable with modest cost premiums, which are further mitigated by international coordination. Differences in the deployment of renewables across scenarios tend to offset at the regional level; however, variability at the country level suggests that national decarbonization pathways are sensitive to technology characteristics. Achieving mitigation goals without coordination requires additional generation capacity, at more than triple the added cost of coordinated planning scenarios (14.7-22.8 vs. 3.5-7.0 billion USD). Beyond South America, these results are relevant to regions looking to meet emissions targets through greater international cooperation.