A renewable energy developer has secured access to land near a transmission substation. The initial idea looks straightforward – install a 100 MW Battery Energy Storage System, charge the batteries when power is inexpensive and discharge them during high-demand periods.
A few battery suppliers are contacted. Quotations arrive. One vendor recommends 100 MW / 200 MWh, another suggests 100 MW / 400 MWh, and a third offers a lower upfront price but with different degradation and warranty conditions.
Suddenly, the project is no longer about buying batteries.
The developer needs to answer much bigger questions. Should the project be designed for two-hour or four-hour storage? How much usable capacity will remain after 8 or 10 years? Will additional battery modules need to be installed later? Who pays for charging electricity? What will the transmission connection cost? Can the project receive Viability Gap Funding? How much debt can the cash flow safely support?
This is where a Grid-Scale BESS DPR becomes important.
A Detailed Project Report for a Battery Energy Storage System is not simply a machinery list with an estimated project cost. It is a complete technical, commercial and financial plan that helps a developer understand whether the proposed BESS project can actually operate, earn revenue and remain financially viable over its operating life.
India’s BESS market is expanding rapidly as renewable energy capacity increases. National planning estimates indicate a requirement of around 8.68 GW / 34 GWh of BESS by 2026-27, increasing to approximately 47.24 GW / 236 GWh by 2031-32.
For project developers, investors and infrastructure companies, this creates a major opportunity. But the opportunity only makes sense when the project is properly sized and financially structured.
A grid-scale Battery Energy Storage System stores electricity in batteries and supplies that electricity back to the grid when required.
The most important numbers in any BESS project are MW and MWh.
MW represents the amount of power that the system can deliver at a particular time.
MWh represents the amount of energy that can be stored and supplied over a period.
For example, a 100 MW / 200 MWh BESS can theoretically deliver 100 MW for approximately two hours. This is therefore commonly described as a two-hour storage system.
A 100 MW / 400 MWh project would provide approximately four hours of storage.
This difference can completely change the project cost.
Two projects may both be described as 100 MW BESS projects, but a 400 MWh project can require significantly more battery capacity than a 200 MWh system.
A proper DPR should therefore establish:
The project should not move into procurement until these assumptions are reasonably clear.
Solar and wind power are variable by nature.
A solar plant may generate maximum electricity between late morning and afternoon, while electricity demand may remain high in the evening. This creates a gap between renewable generation and electricity demand.
Battery storage helps shift electricity from one period to another.
For example, a BESS can charge between 11:00 AM and 3:00 PM, when solar generation is high, and discharge between 6:00 PM and 10:00 PM, when electricity demand may be stronger.
Storage can also support the electricity system through services such as:
Government support has also accelerated BESS deployment.
Different BESS support programmes together represent approximately 43.8 GWh of storage capacity, while one major programme provides Viability Gap Funding of up to ₹18 lakh per MWh for eligible projects.
This has attracted interest from renewable energy developers, utilities, infrastructure investors and independent power producers.
A bankable BESS DPR should connect technical design with commercial and financial assumptions.
A project cannot be financially evaluated properly if its battery configuration is unclear. Similarly, battery capacity cannot be finalised without understanding how the system will earn revenue.
A strong BESS DPR generally contains the following sections.
The executive summary provides a quick understanding of the complete project.
It should explain:
For example, a project could be structured as:
100 MW / 200 MWh standalone BESS
The developer may plan to connect the project to a nearby 220 kV substation and operate under a long-term storage service agreement.
That information immediately gives lenders and investors a clearer understanding of the business model.
One of the most common questions from developers is:
What is the cost of a BESS project in India?
There is no single correct cost per MW.
BESS cost depends heavily on MWh capacity, storage duration, battery chemistry, project location, warranties, grid infrastructure and EPC scope.
Recent large-scale projects and tenders indicate that storage costs have fallen significantly.
Competitive procurement has shown storage service costs near ₹2.1 per kWh in cases where systems operate at approximately two cycles per day.
At around 1.5 cycles per day, the effective storage cost may move closer to approximately ₹2.8 per kWh, depending on the commercial arrangement.
These numbers should not be confused with EPC construction cost.
A BESS DPR should calculate capital investment from individual project components rather than simply applying a market cost per MW.
Battery modules normally form the largest part of the project investment, but they are only one component.
A complete project cost may include:
A quotation that appears 10 percent cheaper may exclude transmission infrastructure, civil works or augmentation obligations.
This is why vendor quotations should be normalised before comparison.
Consider an illustrative developer planning a 100 MW / 200 MWh standalone BESS.
The system is expected to operate for approximately two hours at rated power.
The developer receives quotations from three suppliers.
Supplier A offers a lower upfront cost but provides limited long-term capacity guarantees.
Supplier B offers a higher initial price but includes stronger degradation guarantees and part of the augmentation requirement.
Supplier C provides an EPC package but excludes the transmission bay, grid interconnection and future battery additions.
If the developer compares only initial project cost, Supplier A may appear attractive.
But the DPR calculates the project over 15 years.
It identifies that additional battery capacity may be required during the operating period to maintain contracted MWh capacity.
Once future augmentation is included, the apparent cost difference between the vendors becomes much smaller.
This demonstrates why BESS procurement should be evaluated using lifecycle economics rather than only initial CapEx.
Battery degradation is one of the most important variables in a BESS financial model.
A battery installed today will not normally provide exactly the same usable capacity after thousands of charge and discharge cycles.
Capacity gradually reduces because of factors such as:
Consider a simplified example.
A project installs 200 MWh of usable capacity.
If effective usable capacity falls to around 180 MWh after several years, the project may no longer meet a contractual requirement of 200 MWh.
The developer may therefore need to add additional battery modules.
This process is called augmentation.
The DPR should estimate when augmentation may be required and how much it may cost.
Without this calculation, a project can look profitable during the first few years but face large unexpected capital expenditure later.
BESS revenue depends on the project structure.
Not every project earns revenue in the same way.
A standalone BESS may earn fixed capacity payments under a storage agreement.
Another project may earn revenue through market arbitrage.
A renewable energy project may use storage to deliver firm power during specific hours.
Other projects may participate in ancillary services depending on market rules and contractual eligibility.
Potential revenue sources include:
However, these revenues should not automatically be added together.
The DPR must confirm whether the commercial agreement allows each revenue stream.
Consider a 100 MW BESS project receiving a fixed monthly capacity payment.
If the project earns ₹2 lakh per MW per month, the annual gross capacity revenue would be approximately:
100 MW x ₹2 lakh x 12 months
= ₹24 crore per year
If the tariff increases to ₹2.5 lakh per MW per month:
100 MW x ₹2.5 lakh x 12
= ₹30 crore per year
A difference of only ₹50,000 per MW per month therefore changes annual gross revenue by approximately ₹6 crore.
For a 15-year project, this difference can materially affect project valuation.
A financial model should therefore run multiple sensitivity cases instead of relying on one tariff assumption.
The financial section should explain whether the project can generate sufficient cash flow to support debt and equity investment.
Typical projections include:
The model should normally project at least 10 to 15 years, depending on the expected contract period and asset life.
A base-case model alone is not enough.
Battery storage economics can change significantly when even one assumption changes.
A proper DPR should test several cases.
For example:
This helps investors understand how resilient the project is.
A project with a strong IRR in the base case may become difficult to finance if the downside case produces weak DSCR.
Viability Gap Funding can reduce the effective capital requirement of an eligible project.
One major BESS support programme provides approximately ₹18 lakh per MWh of VGF for eligible capacity.
Consider a hypothetical eligible 200 MWh project.
200 MWh x ₹18 lakh
= ₹36 crore
If the project qualifies for the programme, ₹36 crore of VGF could materially change the funding structure.
However, VGF should not automatically be assumed in the DPR.
The project must first establish:
The financial model should ideally show two cases.
Case 1 – Project without VGF
Case 2 – Project with confirmed VGF
This allows investors to understand whether the project remains viable without subsidy support.
A technically suitable BESS site may still become financially unattractive if grid connection is expensive.
For example, consider two sites.
Site A is located 1 km from an available substation.
Site B has cheaper land but requires a 15 km transmission line and major substation upgrades.
The land saving at Site B may be small compared with the additional electrical infrastructure cost.
The DPR should therefore evaluate:
Grid assessment should happen before land acquisition is finalised wherever possible.
Grid-scale lithium battery systems require serious fire and thermal management planning.
A BESS site may contain hundreds of battery racks and several battery containers.
A thermal event in one battery module must be detected and controlled quickly to reduce the possibility of propagation.
Safety planning may include:
India has also introduced BESS-specific technical and safety requirements through CEA amendments notified in 2026, with important provisions scheduled to take effect from 1 April 2027.
Developers planning projects that will be constructed or commissioned around this period should consider these requirements during engineering instead of making design changes later.
A BESS project must also plan for what happens when batteries reach the end of their useful operating life.
Battery replacement can create a large quantity of waste batteries.
India’s Battery Waste Management framework covers industrial batteries and includes Extended Producer Responsibility obligations for applicable manufacturers and importers.
A project that imports battery systems directly should therefore assess whether it becomes responsible for additional regulatory obligations.
The DPR should identify:
End-of-life cost should not be ignored simply because it may arise 10 or 15 years after commissioning.
A grid-scale BESS project generally moves through several stages.
The exact timeline depends on project size, grid approvals, financing and equipment supply.
Typical stages include:
Developers should avoid ordering major battery equipment before the project configuration, grid connection and commercial structure are reasonably finalised.
Before preparing the final financial model, the promoter should be able to answer the following questions:
If several of these questions remain unanswered, the project may still be at the feasibility stage rather than being ready for investment.
Grid-scale BESS is becoming one of the most important infrastructure opportunities in India’s renewable energy sector.
But a BESS project cannot be evaluated using only battery price or cost per MW.
A strong Grid-Scale BESS DPR should connect technical sizing, project cost, grid infrastructure, degradation, augmentation, revenue, VGF, financing, safety and long-term battery management into one integrated project plan.
The difference between a good BESS project and a financially difficult one may come down to assumptions made before procurement.
A developer who properly studies battery degradation, charging cost, grid availability, revenue structure and augmentation requirements can make a much stronger investment decision.
For investors, banks and project promoters, the DPR becomes the document that converts a storage idea into an investment-ready project.
Green Permits supports project developers with:
👉 Planning a Grid-Scale BESS Project? Talk to Green Permits for DPR, feasibility and project financial planning.
Website: www.greenpermits.in
