LCOS Definition

Two batteries with identical hardware can post levelized costs $16/MWh apart. The difference is not the equipment. It is how often the operator cycles it.

Levelized Cost of Storage (LCOS) is the total lifetime cost of a storage asset divided by the total energy discharged over its lifetime, in dollars per megawatt-hour. Where LCOE measures the cost of generating electricity, LCOS measures the cost of shifting it in time.

The formula:

LCOS = (Capital + O&M + Charging Energy + Replacement Costs) / Total MWh Discharged

Two features make LCOS structurally different from LCOE.

First, the denominator is cycle-dependent. How often a battery cycles determines total discharge. A 100 kWh battery cycled once per day for 10 years delivers roughly 365 MWh; the same battery cycled twice per day delivers roughly 730 MWh, but wears out faster. The denominator and the asset lifetime are not independent.

Second, charging cost is a real input. Unlike a generator, storage consumes electricity it did not produce. If the grid charges a battery at $40/MWh and discharges at $80/MWh, that $40 spread must cover all other costs to break even. Ignoring charging cost systematically understates LCOS.

A 10 MW / 40 MWh battery system costs $8 million installed. Over its 15-year life it cycles once daily, accumulates $1.5 million in O&M and replacements, and consumes $3 million worth of charging electricity. Total lifetime discharge: 40 MWh x 365 x 15 = 219,000 MWh.

Before calculating: which cost component do you expect to dominate?

Capital does: $8M of the $12.5M total. LCOS = ($8M + $1.5M + $3M) / 219,000 MWh = $12.5M / 219,000 = $57/MWh

Now suppose the operator cycles the battery twice daily instead of once. Discharge doubles to 438,000 MWh. The cells wear out in 7 years instead of 15, and a mid-life cell replacement (raising replacement costs to $4M) keeps the system running to year 15. Charging energy doubles to $6M.

LCOS = ($8M + $4M + $6M) / 438,000 = $18M / 438,000 = $41/MWh

More cycling lowered LCOS, but only because the denominator grew faster than the costs. Whether that spread is profitable depends entirely on the market price of discharged electricity.

LCOS is the storage analog of LCOE, with a catch: the cycling assumption drives the number, which makes it easy to manipulate. When a vendor or a subsidy application quotes a low LCOS, ask what cycle rate it assumes.

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