For a year, the honest answer to “what does a battery earn in Sri Lanka?” was: nothing, directly. In June 2025 Cabinet approved a rate of Rs. 45.80 per unit for solar delivered to the grid at night from storage. CEB said it would notify the applicable date. The notification never came, the December 2025 implementation deadline passed with no guidelines and no contract amendments, and industry bodies were still waiting in early 2026. The entire case for storage had to be made behind the meter.
That changed on 25 August 2026. PUCSL’s tariff decision of 24 August set an export rate for rooftop solar paired with battery storage, and it is in force.
So the question is no longer whether a battery can earn. It is which of two routes earns more for your building — and the answer is decided almost entirely by what your evening load looks like.
Route one: export from storage, at the new rate
Under the schedule effective 25 August 2026:
- A new rooftop system with battery storage is paid Rs. 45.53 per unit during priority periods for the first fifteen years, then Rs. 15.81.
- An existing system adding storage is paid Rs. 33.51 plus a formula-linked component for the first fifteen years, then the underlying rate.
Set that against plain daytime export. A 40–250 kW system exports at Rs. 17.11. The same unit, stored and delivered in the priority window, is worth Rs. 45.53. That is roughly two and two-thirds times, and it applies whether or not your building is occupied in the evening.
For context, the same decision prices ground-mounted solar with storage at Rs. 20.72 daytime and Rs. 50.10 at night.
Route two: store it and use it yourself
Sri Lanka’s industrial time-of-use tariff, effective 11 May 2026, splits the day into three bands at 400/230 V with contract demand under 42 kVA:
- Peak — 18:30 to 22:30 — Rs. 78.00
- Day — 05:30 to 18:30 — Rs. 39.00
- Off-peak — 22:30 to 05:30 — Rs. 19.00
Look at the peak band hours. They describe the same problem the battery export tariff was designed around: Sri Lanka’s evening demand peak, after the sun has gone.
A unit of stored solar consumed in your own evening peak is worth Rs. 78.00, because that is what you would otherwise pay for it. Exported under the new storage tariff, the same unit earns Rs. 45.53.
Self-consumption in the peak window is worth about 1.7 times what exporting the same stored unit earns. It requires no scheme, no Power Purchase Agreement amendment and no tariff approval, and it happens entirely behind your meter.
Which route your building is on
This is not a preference. It is arithmetic, and your load profile decides it.
If you have a substantial, predictable evening load, self-consumption wins and it is not close. A two-shift factory running into the evening captures Rs. 78.00 a unit against Rs. 45.53. Size the battery to your evening consumption, not to your roof.
If your building empties at five, the picture inverts. An office, a warehouse, a school or a single-shift plant has almost nothing to shift solar into after 18:30. Until August, that meant storage made little sense at all. Now those buildings have a route that did not exist: store the midday surplus and export it in the priority window at Rs. 45.53 rather than dumping it at Rs. 17.11 while the sun is up.
Most buildings sit between the two, and the right design fills the evening load first and exports the remainder. The battery does not have to choose one job — the control strategy does, hour by hour.
A building with a high maximum demand charge may find the case is about demand management rather than energy — using storage to shave the peaks that set the monthly demand charge. That is a third calculation again, and it depends on figures specific to your tariff category.
A site with genuine outage exposure should count backup value separately. It is real, but it is not an energy saving and should not be counted twice.
Why storage moved from marginal to serious
For most of the last decade the argument against batteries was straightforward. Batteries cost money, and exporting was almost free — at Rs. 37.00 a unit under the pre-2024 rates, the grid was a better battery than a battery.
Four things undid that.
Plain export rates fell and then tiered. A commercial system that earned Rs. 37.00 flat in 2022 earns Rs. 17.11 today at 40–250 kW, and Rs. 15.81 above 250 kW.
Retail rates rose. Increases took effect in April 2026 and again in May 2026. The gap between what you pay and what you earn widened from both directions at once.
Export stopped being reliable. CEB began curtailing solar in February 2025 under “Sunny Sunday,” extending it to weekdays and public holidays by January 2026 — three days a week at points, with industry losses estimated around Rs. 2 billion and no compensation paid. In June 2026, systems of 300 kW and above were asked to disconnect over the Poson holiday period. A stored unit delivered in the evening peak is not exposed to midday oversupply curtailment in the same way.
And now a storage rate exists. The missing piece for a year was a number. There is one.
What the rules say about batteries
In July 2026, PUCSL published a Regulatory Framework for Rooftop Solar PV Systems and Battery Energy Storage Systems, setting out technical requirements in detail for the first time. The August tariff decision supplies the commercial terms that framework left pending.
The provisions that affect specification:
- Lithium-ion only, minimum IP54 enclosure rating, maximum 1500 V DC.
- Battery sizing is capped — usable capacity in kWh must not exceed five times the rated continuous inverter power in kW. A 40 kW inverter therefore supports up to 200 kWh usable. Exceeding it requires a written technical assessment from a Chartered Electrical Engineer.
- Cycle life minimums — 8,000 cycles at 80% depth of discharge for commercial and industrial systems, with at least 80% capacity retention at end of life and 85% round-trip efficiency.
- Systems with inverters above 50 kW must provide communication capability for utility monitoring and control.
- Export limitation and dynamic power management are required where inverter capacity exceeds approved export capacity. Specify this at tender stage — retrofitting export control is expensive.
- Full battery management system, fire suppression, an external emergency shutdown switch, and twelve months of data retention.
One caveat worth stating plainly: the framework’s own annexures still mark the Standard Power Purchase Agreement and the Code of Practice for battery installation as pending. Confirm the contracting position with your utility before signing on the strength of the tariff alone.
What to ask for
If you are evaluating a hybrid proposal, four questions get you most of the way:
- What is the assumed peak-window consumption? The whole case rests on it. If nobody has looked at your evening load, the payback figure is guesswork — and it decides which of the two routes you are on.
- Which route is this proposal modelling — self-consumption at Rs. 78.00, export at Rs. 45.53, or a mix? Ask to see the split. A proposal that quietly counts the same unit twice is not a proposal.
- Does the battery sizing comply with the five-times-inverter rule? If not, where is the Chartered Engineer’s assessment?
- What is the assumed cycle life, and does it meet the 8,000-cycle C&I standard? A cheaper battery that reaches end of life in year seven changes the answer entirely.
And one thing to check rather than assume: the storage tariff sits on the same schedule as the export bands, and that schedule is valid until 24 February 2027. Ask what happens to the modelled revenue if the rate is revised at the next review.
Have the calculation done properly
First Energy designs hybrid and storage systems alongside a decade of solar EPC work, and has followed every one of these tariff and regulatory changes as they happened — including the one that landed this week. If you want to know whether storage makes sense for your building, and which route it should take, based on your actual load profile and tariff category rather than a template, get in touch for an assessment.
Sources: PUCSL rooftop solar PV tariff schedule effective 25 August 2026 · PUCSL Regulatory Framework for RTSPV and BESS, 31 July 2026 · PUCSL Decision on Electricity Tariffs, May 2026 · PUCSL Analysis on Rooftop Solar Integration and Industry Growth (2026) · EconomyNext, Newswire.lk, Lanka Business Online.