Indonesia's 100 GW Solar Plan Meets Grid Reality: The Storage and Transmission Gap

In September 2026, Indonesia's Energy Minister Bahlil Lahadalia confirmed that the government will revise the Electricity Supply Business Plan (RUPTL), the 10-year roadmap that utilities, lenders, and manufacturers actually build procurement and financing around, to accommodate a 100 gigawatt-peak solar program that President Prabowo Subianto announced in June 2025 ^[1][2]. The move is administratively sensible: a program of that scale cannot move through grid-connection, financing, and equipment queues on presidential instruction alone. It needs a regulatory home in the document that shapes national infrastructure investment. But the revision exposes a widening gap between solar ambition and grid readiness that Indonesia has not yet closed.

Start with the numbers. The original RUPTL 2025-2034 approved in May 2025 targeted 69.5 GW of total capacity additions, including just 17.1 GW of solar ^[4]. The new 100 GW solar program represents a sixfold increase over that original solar target. State utility PLN has already submitted a revision covering more than 50 GWp of solar and 142 GWh of battery energy storage systems ^[4]. Yet the initial phase alone is estimated to require around 33 GW of battery energy storage systems (BESS), compared to the 6 GW of batteries the full RUPTL 2025-2034 plans over an entire decade ^[5]. The grid expansion is equally strained: the plan includes 47,758 circuit-kilometers of new transmission lines with smart-grid technology, but this was designed for a more modest renewable buildout ^[1]. Indonesia's domestic solar module production capacity stands at 4.8 GWp per year, meaning an installation pace moving significantly faster than domestic supply ^[5].

The financing burden is the deeper constraint. The Directorate General of Renewable Energy estimates total renewable energy investment needs through 2034 at USD 90 billion (about USD 90 billion), and that estimate predates the 100 GW solar acceleration ^[5]. The cost of battery storage at scale, a prerequisite for integrating that much solar into a 24-hour grid serving an archipelago with seasonal cloud cover, has not been financed. Without storage, peak solar hours produce curtailment and grid instability; without grid expansion, solar capacity sits idle at the periphery.

The deeper issue is that this is not purely a solar story. The same RUPTL 2025-2034 that originally targeted only 17.1 GW of solar by 2034 also planned a 40 percent increase in fossil fuel generation, from 295 TWh to 407 TWh, with 16.6 GW of coal and gas capacity in the pipeline ^[8]. The 100 GW solar program is a policy layer added on top of an infrastructure roadmap still dominated by thermal power. Least-cost planning, the standard practice in Australia, parts of Europe, and increasingly in developing-nation utilities, would ask: which mix of solar, storage, transmission, and thermal capacity actually minimizes total system cost and carbon? Indonesia is instead treating solar as a target to be grafted onto an existing fossil-first plan ^[6].

The parallel here is instructive. When Australia accelerated rooftop solar in the 2010s, it did so within a framework that was already accounting for transmission needs and storage requirements, and it offset those costs by retiring coal capacity ahead of economic life ^{[background library]}. Germany's Balkonkraftwerk (plug-in balcony solar) succeeded because it was a small, distributed addition to a grid already planning for large-scale wind and gas backup. Indonesia is attempting to add 100 GW of distributed generation to a grid designed around centralized coal and gas plants, without yet having financed the storage, transmission, or the retirement schedule that makes that transition work. The revision to the RUPTL is a necessary step. It is not a sufficient one.

What operates at scale elsewhere: Chile's 2024 electricity reform embedded a least-cost planning requirement into all 10-year grid roadmaps, forcing utilities to choose renewables plus storage over thermal when the math favors it. Vietnam's early-2020s rooftop solar boom (9 GW added in 2020 alone) was so rapid and unplanned that the grid operator imposed retroactive curtailment and tariff cuts, freezing the market. Indonesia is at a decision point: embed the 100 GW target into a comprehensive least-cost framework that retires coal on schedule and finances storage upfront, or watch this become the next Vietnam, rapid deployment followed by policy whiplash and investor retreat.