Ask most people what Tesla does and they will say electric cars. That is true, but the company's own annual report tells a two-part story. In its Form 10-K for the year ended December 31, 2019, Tesla describes itself as operating in two reportable segments: automotive, and 'energy generation and storage.' The second one is the subject of this explainer.
So what is in it? The filing groups two kinds of product together. The first is solar generation — the rooftop solar systems Tesla sells and leases, and the Solar Roof, a roof made of photovoltaic tiles. The second is energy storage: batteries that hold electricity for later use. Tesla's home battery is the Powerwall; its larger commercial and utility batteries are sold as Powerpack systems. The logic of bundling generation and storage is that they are complementary — solar makes power when the sun shines, and a battery lets you use it after dark or sell it back when it is worth more.
Why report it as a separate segment at all? Under accounting rules, a company breaks out a 'reportable segment' when management runs it as a distinct business and reviews its results separately. Tesla does exactly that: the energy business has its own revenue line, its own cost of goods, and its own gross margin in the financial statements. Reading those lines is the only honest way to size the business, because the headline 'Tesla revenue' number is overwhelmingly the cars.
The strategic idea the filing keeps returning to is integration. A Tesla customer could, in principle, generate power on the roof, store it in a Powerwall, drive on it in the car, and manage all of it through Tesla software. Whether that vision pays off is a question for future quarters; the document only tells you the pieces exist and are sold today.
For a reader trying to understand the sector, the useful habit is to treat the energy segment on its own terms rather than as a rounding error attached to the cars. The grid needs storage, utilities are starting to buy it at scale, and Tesla is one of a handful of names with a shipping product. The 10-K does not promise where that goes — but it is the document that proves the business is real and tells you how to find its numbers.
Whenever an energy claim about Tesla crosses your screen, the discipline is the same: go to the segment disclosure in the annual report rather than the keynote. The filing — indexed and retrievable through services such as EdgarBeast — is the record. The slide deck is the sales pitch.