It surprises some readers that a car company's annual report devotes serious attention to giant stationary batteries that never move. But energy storage is not a side note in these filings — it is a second business with its own products, customers, and economics, and the filing treats it as such. Reading it as a distraction means missing how the company actually makes money.
Tesla's Form 10-K for 2023, filed January 29, 2024, attributes a gain in its energy business to "an improvement in our Megapack gross margin from lower average cost per MWh and a higher proportion of Megapack." Its 2024 quarterly filings add that for Megapack, "energy storage deployments can vary meaningfully quarter to quarter depending on the timing of" projects, and reference the ongoing ramp at its Megafactory in Lathrop, California. The 10-K is on sec.gov, surfaced through EdgarBeast.
Start with the unit. Grid storage is measured in energy delivered — megawatt-hours (MWh) — not in vehicles. The filing's reference to "average cost per MWh" is the storage equivalent of a per-vehicle cost: it tells you how cheaply the company can build a unit of stored energy. When that cost falls, the margin on each project improves, which is precisely the dynamic the 10-K describes.
Next, the lumpiness. The filing's warning that deployments "can vary meaningfully quarter to quarter" is a crucial reading instruction. Grid projects are large, scheduled, and recognized when delivered, so a single quarter can swing on the timing of a few big installations. Judging the storage business on one quarter is like judging a homebuilder on one closing — the cadence is project-driven, not steady like retail car sales.
The economics differ from cars in a way that matters. Vehicles sell to many individual buyers at relatively steady volumes; grid storage sells to utilities and developers in big, irregular chunks. So the storage segment's margin depends heavily on cost per MWh and product mix — the filing specifically credits a "higher proportion of Megapack" — rather than on the steady throughput logic of a car line.
For a reader, the lesson is to unbundle the company. An EV maker that also builds grid storage is running two businesses with two different rhythms and two different cost units. Tesla's 2023 filing makes the storage economics explicit enough — cost per MWh, lumpy deployments, mix-driven margin — that you can analyze it on its own terms, which is the only way to read it fairly.