So far, we’ve looked at what a BESS can do and the different ways it can create value.
But there is a step between: This battery can provide a service.
and: This battery generates ₹X crore a year.
That step is quantifying the economics.
Let’s start with a simple question:
How do the MW and MWh of a battery actually translate into money?
Start with the asset
Consider a: 100 MW / 200 MWh BESS
The two numbers tell us different things.
100 MW = the maximum power the battery can charge or discharge at a given moment.
200 MWh = the amount of energy it can store.
Therefore:
200 MWh ÷ 100 MW = 2 hours
This is a: 2-hour BESS
But neither 100 MW nor 200 MWh tells us how much money the project makes.
For that, we need to know:
- what the battery is being paid for
- how much of its capacity is contracted
- how much energy it actually delivers
- what the applicable price is
- how often it operates
This is where the commercial model matters.
1. Capacity / availability revenue
Suppose the BESS is contracted under an availability-based structure.
Imagine the contracted payment is: ₹3 lakh / MW / month
For a 100 MW BESS:
100 MW × ₹3 lakh/MW/month
= ₹3 crore/month
Annualised: ₹3 crore × 12
= ₹36 crore/year
Notice what happened.
We didn’t need to calculate how many MWh the battery discharged.
The payment was based primarily on:
How much capacity the BESS makes available.
This is fundamentally different from merchant arbitrage.
The battery is being paid for capability and availability, subject to the contract’s performance requirements.
And that distinction will become very important later when we discuss predictability of cash flows and project finance.
2. Contracted energy delivery
Now consider a different commercial structure.
Suppose a solar + BESS project is contracted to deliver electricity at:
₹5,000/MWh
And suppose the project delivers:
200 MWh
during a particular period.
The associated revenue is:
200 MWh × ₹5,000/MWh
= ₹10 lakh
** But this is only gross revenue. The project still has costs associated with producing or procuring, storing and delivering that electricity.
Here the payment is linked to:
the amount of electricity delivered.
The BESS may be an important part of making that delivery possible, but the customer may simply pay for the contracted electricity rather than separately paying the battery a “storage fee.”
This is why looking only at the battery’s equipment cost can sometimes be misleading.
The battery can be one component of a larger power-delivery business model.
3. Merchant energy arbitrage
Unlike the contracted energy-delivery example above, here the BESS is exposed directly to market prices. The electricity it buys becomes an immediate cost of the arbitrage transaction.
Now consider a BESS operating against market prices.
Suppose it buys: 200 MWh at ₹3,000/MWh
Charging cost:
200 × ₹3,000
= ₹6 lakh
Later, suppose it can sell the resulting energy when the market price is: ₹7,000/MWh
But remember:
The battery isn’t 100% efficient.
Assume round-trip efficiency of: 90%
So approximately:
200 MWh × 90% = 180 MWh
is available for delivery.
The value of that delivered energy is:
180 × ₹7,000
= ₹12.6 lakh
Therefore:
Gross arbitrage margin
₹12.6 lakh − ₹6 lakh
= ₹6.6 lakh
This is the economics of one simplified charge-discharge cycle.
And importantly:
₹6.6 lakh is not profit.
We have not yet accounted for:
- degradation
- O&M
- auxiliary consumption
- network or market charges
- taxes
- financing costs
- augmentation
We’ll come to those later.
The same battery can therefore have very different economics
Look at what changed.
Capacity model
100 MW × ₹/MW/month
↓
Payment for availability
Energy-delivery model
MWh delivered × ₹/MWh
↓
Payment for electricity delivered
Merchant model
Energy purchased × market purchase price
versus
Energy delivered × market selling price
↓
Gross value created from the price spread, after accounting for efficiency
The physical battery could be identical.
But the commercial model changes how the project’s revenue and economics are determined.
That is one of the most important ideas in understanding storage economics.
MW does not equal MWh
This distinction is worth slowing down for.
A 100 MW / 200 MWh battery can deliver: 100 MW for 2 hours
But a 100 MW / 400 MWh battery can deliver: 100 MW for 4 hours
The power capability is identical.
The energy capacity is not.
So if a service requires: 100 MW for four hours
the first battery cannot provide the same service as the second.
This is why the economics of storage cannot be understood using ₹/MW alone or ₹/MWh alone.
The right denominator depends on what the customer is buying.
Utilisation changes the economics
Now return to our merchant example.
We calculated:
₹6.6 lakh
of gross arbitrage margin for one simplified cycle.
What if the battery could achieve the same economics every day?
₹6.6 lakh × 365
≈ ₹24.1 crore/year
But this assumes something extremely important:
The battery has a profitable opportunity every day.
Real markets don’t work that neatly.
There may be days when:
- the price spread is too small
- the battery is already committed elsewhere
- the battery needs to preserve state of charge
- maintenance is required
- market conditions don’t justify cycling
- cycling would create too much degradation relative to the value created
Suppose instead that the battery achieves 250 equivalent full cycles per year at the same average gross margin per cycle.
Then: ₹6.6 lakh × 250
= ₹16.5 crore/year
Same battery.
Same assumed prices.
Same efficiency.
But a different utilisation level.
This is why Installed capacity does not automatically determine revenue.
The asset must actually be used in ways that create economic value.
This is where revenue stacking comes back
The battery may not spend all of its available capability on arbitrage.
It might instead allocate some of its capability to:
- capacity / availability
- ancillary services
- renewable energy shifting
- arbitrage
- behind-the-meter savings
The optimizer therefore has a bigger question to solve:
Which use of the battery generates the greatest economic value at this point in time?
That decision depends on:
- Price
- Contractual commitments
- State of charge
- Efficiency
- Degradation
- Future opportunities
- Technical constraints
So the revenue calculation isn’t just:
MW × price
It is the result of how the physical asset is operated within its commercial environment.
From a single transaction to annual revenue
We can now build the basic bridge:
Physical asset
↓
MW + MWh
↓
Operating strategy
↓
Utilisation
↓
Energy / capacity delivered
↓
Applicable price or payment
↓
RevenueThat is the basic economic engine of a BESS. But we have deliberately stopped at revenue because revenue is only the top line.
A BESS can generate substantial gross revenue and still have poor economics if the costs of generating that revenue are too high.
And storage has some very specific costs.
For example:
- Every cycle can contribute to battery degradation.
- Every year requires operation and maintenance.
- Energy is lost through inefficiency.
- The battery may eventually need augmentation or replacement.
- And once we introduce financing, there is another layer: The project also has to service its debt.
So there are now several different layers:
- Revenue: what the project earns from its commercial arrangements
- Costs: what it spends to operate and maintain the asset
- Cash flow: what is actually left after the relevant cash expenses and investments
- Returns: what the investors ultimately earn on the capital they put in
So the next question becomes much more interesting:
Of the ₹X crore a BESS generates, how much does the owner actually keep?
That’s where we move from revenue to profitability and cash flow.