# Storage is priced per kWh discharged, not per kWh installed

> The number that decides whether a battery or a thermal store pays is the cost of each kWh it actually delivers over its life: cycles, depth, degradation. Why arbitrage rarely carries the case and what block matching does instead.

Canonical: https://joulewise.com/insights/storage-is-priced-per-kwh-discharged  
Publisher: jouleWise Advisory Services Pvt Ltd, Noida, India · Spain  
Reviewed: 2026-10-08  
Status: company page

## In short

A battery and a hot-water tank do the same job: they decide when you get to use energy you already have. Renewable generation arrives when the resource is available, not when the plant is consuming; a factory's heat demand follows its shifts, not the sun. Without somewhere to put the surplus, it is spilled or banked on unfavourable terms while the plant imports at tariff hours later. Storage is what turns contracted capacity into consumed units.
*Published 2026-10-08 · Energy storage · the economics*

## Storage does not create energy

A battery and a hot-water tank do the same job: they decide when you get to use energy you already have. Renewable generation arrives when the resource is available, not when the plant is consuming; a factory's heat demand follows its shifts, not the sun. Without somewhere to put the surplus, it is spilled or banked on unfavourable terms while the plant imports at tariff hours later. Storage is what turns contracted capacity into consumed units.

## The only price that matters

Capital cost per kWh installed is the figure on the quotation, and it is the wrong one to decide on. What matters is cost per kWh discharged over the asset's life: capital and operating cost divided by the energy the store will actually deliver, which depends on how many cycles it runs a year, how deep each cycle goes, and how fast it degrades. Two batteries with the same price per installed kWh can differ by half on that measure. REplanner uses a default of ₹4.00 per kWh discharged, with lithium iron phosphate near ₹7 today and sodium-ion trending towards ₹2.50, at 330 cycles a year.

## Four jobs, in order of value

Block matching: shifting contracted generation into the fifteen-minute blocks where consumption actually sits. This is the job that raises renewable share rather than just capacity, and it is where most of the value usually is. Peak shaving: cutting the contract demand the plant is billed on and riding through the short peaks that set it. Ride-through: holding critical utilities across a grid disturbance where an outage costs a batch rather than an hour. And arbitrage: charging cheap and discharging dear, which is real but modest and the first return to disappear when spreads narrow. Storage justified on arbitrage alone tends to disappoint.

## Battery or thermal?

Whichever moves the constraint. If the problem is heat arriving at the wrong time — a heat pump that should run in solar blocks for a factory that needs hot water on the evening shift — a hot-water store is usually cheaper per unit shifted than a battery, and simpler. If the problem is demand charges or electrical matching, a battery. On most sites with heat pumps the answer is both, sized to different jobs.

## Sizing needs block data

Storage sized against annual figures is guesswork. It is a block-by-block question and needs metered consumption at fifteen-minute resolution, the demand-charge structure, the existing or planned renewable contracts and the criticality of loads. What 5 MWh physically holds — two banks of racks, 48 packs, 4,992 cells, busbars, cooling and the electrical path — is what BESS Studio exists to show, so that a buyer sees the thing before sizing one.

**Try it:** [See what 5 MWh holds in BESS Studio](https://joulewise.com/studios/bess)
## Questions and answers

**How should I compare storage options?**  
On cost per kWh discharged over the asset's life — capital and operating cost divided by energy actually delivered, which depends on cycles, depth and degradation — not on capital cost per kWh installed.

**Is battery arbitrage a good business case?**  
Rarely on its own. It is real but modest and the first return to vanish when price spreads narrow. Block matching and peak shaving usually carry the case.

**Battery or thermal storage?**  
Whichever moves the constraint: a thermal store for heat arriving at the wrong time, a battery for demand charges or electrical matching. Often both.

## Related

- [See what 5 MWh holds in BESS Studio](https://joulewise.com/studios/bess)
- [Energy storage](https://joulewise.com/solutions/energy-storage)
- [REplanner](https://joulewise.com/studios/replanner)

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