Rooftop Solar + Storage: A Smarter Path for Sri Lanka’s Grid Stability
Sri Lanka’s rooftop solar programme, initiated under Suriya Bala Sangramaya, has grown impressively, now reaching 1,700 MW across 100,000 households and buildings. This expansion demonstrates consumer willingness to invest when incentives are aligned. However, recent events such as the February 2025 grid tripping caused by midday excess exports show that unmanaged rooftop capacity poses challenges.
To address this, the Ceylon Electricity Board (CEB) has turned to large-scale battery tenders, including a proposed 640 MWh BESS (Battery Energy Storage System) to absorb surplus solar. Yet, the extended deadline of the current tender suggests that investor appetite is weak, given strict requirements such as land proximity to substations, high upfront capital, and a short 10-year recovery window.
Better Alternative: Distributed Batteries with Rooftop Solar
Instead of centralised storage, Sri Lanka can unlock hidden capacity in existing rooftop systems by encouraging households to install subsidised batteries with a guaranteed evening peak tariff: 40 per cent daytime use, 60 per cent shiftable: If 40 per cent of rooftop output is consumed directly during the day, the balance 60 per cent (1,000 MW) can be stored and dispatched in the evening peak.Consumer incentive: By paying an attractive peak export tariff (e.g. LKR 45.80/kWh or better), CEB enables households to earn income, ensuring strong adoption.No land requirement: Unlike utility BESS, no additional land near substations is needed.No CEB capital cost: Consumers invest in batteries, with only tariff support/subsidy required.Direct savings: Evening solar-fed storage offsets expensive diesel and fuel oil generation, reducing forex outflow.
Why Distributed Storage Wins
Cost: Decentralised batteries are paid for by consumers, while centralised BESS requires CEB (and national debt) financing.Scalability: Every new rooftop system can add incremental capacity, avoiding large, one-time projects.Equity: Consumers share in the economic benefits, increasing public support for renewable adoption.Resilience: Thousands of distributed batteries enhance grid resilience better than single, centralized sites.
Conclusion
Sri Lanka faces a pivotal decision. The 640 MWh BESS tender, already struggling to attract bidders, represents a heavy, centralised approach with limited flexibility. In contrast, leveraging 100,000 existing rooftop systems through subsidised batteries and peak-time tariffs would achieve the same technical objective—absorbing daytime solar and delivering peak-time power, while avoiding public debt, freeing land, and rewarding citizens.
This is not just a grid solution, it is a national energy strategy, aligned with the government’s vision for Community Energy Cooperatives under the NPP Manifesto.
(The writer is an Innovator and Patent holder for Energy Storage Systems). He can be reached at jeremyF@smarthome.lk)
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