BEYOND THE 100% ASSUMPTION: ADJUSTING OnSSET TO REFLECT GRID RELIABILITY COSTS

This report describes two new methodological updates to the Open-Source Spatial Electrification Tool (OnSSET) designed to account for grid unreliability. While standard OnSSET modelling assumes 100% reliability for grid extensions, these updates introduce the Cost of Non-Served Energy (CNSE) and diesel back-up system proxies to more accurately reflect the costs of power outages. A case study in eastern Uganda demonstrates that incorporating these reliability metrics shifts the 'least-cost' electrification pathway away from grid extension and toward decentralized off-grid solutions.

• The standard OnSSET model assumes grid extension provides 100% reliability, which is not reflected in its capital expenditure (CAPEX) or electricity cost calculations, whereas off-grid systems are sized with reliability requirements of 95-99%.
• The Cost of Non-Served Energy (CNSE) approach applies a parametric economic penalty for outages based on reliability indices like SAIDI. In a Uganda case study, this caused minor technology shifts from grid connections to solar home systems (SHS) but had limited impact on total investment estimates because it acts as a shadow price.
• The Diesel Backup option models the explicit CAPEX and OPEX of generators used to cover supply gaps. In the Uganda case study, this approach led to more significant shifts from grid extension to off-grid solutions and increased the total estimated investment of the least-cost scenario by approximately 20%.
• The CNSE approach is limited by its 'value-laden' nature, as there is no standardized method for calculating the economic value of lost load, and it cannot capture sectoral differences (e.g., higher costs for businesses versus residential users) at the settlement level.
• The diesel backup approach relies on the assumption that all customers use generators to cover unmet demand, which may oversize systems for households and undersize them for critical loads like health facilities due to the use of a generic average-to-peak load ratio.
• In the Uganda case study baseline (100% reliability), the total capital investment was 2.2 billion USD, with 65% allocated to grid extension, 4% to grid densification, 24% to solar home systems, and 8% to solar PV mini-grids.

APA

Sustainable Energy for All (n.d.). BEYOND THE 100% ASSUMPTION: ADJUSTING OnSSET TO REFLECT GRID RELIABILITY COSTS. https://www.seforall.org/system/files/2025-12/GridReliaiblityOnSSETWhiteReport.pdf

Chicago

Sustainable Energy for All. BEYOND THE 100% ASSUMPTION: ADJUSTING OnSSET TO REFLECT GRID RELIABILITY COSTS. n.d. https://www.seforall.org/system/files/2025-12/GridReliaiblityOnSSETWhiteReport.pdf.

Wikipedia

{{cite report |author=Sustainable Energy for All |title=BEYOND THE 100% ASSUMPTION: ADJUSTING OnSSET TO REFLECT GRID RELIABILITY COSTS |url=https://www.seforall.org/system/files/2025-12/GridReliaiblityOnSSETWhiteReport.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{sustainableenergyforallndbeyond, author = {{Sustainable Energy for All}}, title = {{BEYOND THE 100\% ASSUMPTION: ADJUSTING OnSSET TO REFLECT GRID RELIABILITY COSTS}}, institution = {Sustainable Energy for All}, url = {https://www.seforall.org/system/files/2025-12/GridReliaiblityOnSSETWhiteReport.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }