Generac makes the generator that kicks in when the power cuts out, and its sales had gone nowhere for two years. Then Amazon signed a supply deal with it on Wednesday evening. By Thursday premarket the stock was quoted near $236 against Wednesday's close of $175.11 — up roughly 35%, as reported by Benzinga and MarketWatch.

What happened

Generac's 8-K, filed with the SEC on 16 September, is unusually specific. It signed a long-term supply agreement with Amazon for backup generators for Amazon's data centres, with initial deliveries expected to total $2.4 billion across 2027 and 2028. The headline "$8 billion" is a different thing: it is the cap on how much Amazon can pay before a warrant stops vesting.

Why it moved

Two reasons, and they are not the same one.

The first is size. Generac's entire commercial & industrial line did $1.46 billion of sales in all of 2025. The scheduled $2.4 billion over two years is about $1.2 billion a year — roughly 82% of that whole line, from one customer, on top of what already exists. Total 2025 revenue was $4.21 billion, down 2%.

The second is the warrant — the part the headline number hides. Generac issued Amazon a warrant over 1,693,745 shares at an exercise price of $200.9266, running to 16 September 2033. Only 307,954 shares vested immediately, about 18%. The rest vests in tranches as Amazon actually pays, up to $8 billion cumulative. So Amazon hasn't committed to $8 billion of generators; it has taken an option to become a shareholder if and only if it spends that much. Note the strike is about 15% above Wednesday's close — Amazon paid nothing and takes equity upside only above the pre-deal price. Fully exercised it is 2.9% of the 59.0 million shares outstanding at 31 July.

The business

This deal touches the smaller half of Generac. In 2025 residential products — home standby units sold through dealers — were 53.8% of sales at $2.27 billion and fell 7%. Commercial & industrial was 34.6% at $1.46 billion and grew 5%; the rest is parts, service and energy-technology. Domestic was 82.5% of sales. So: a US home-generator company with an industrial arm attached. The arm just got a very large customer; the house business is still the bigger number, and it is shrinking.

Valuation

At Wednesday's close the market cap was $10.33 billion on a trailing P/E of 40.22 (EPS $4.35) and a forward P/E of 17.68, as reported by StockAnalysis. The trailing number is high because earnings fell 27.8%, not because the price ran. For scale: Cummins, a $72.62 billion engine and power-generation maker, is on 26.96; Vertiv, the $92.17 billion data-centre power and cooling name, on 54.18. Generac's own P/E ran from about 16 to 62 across 2021–2025 on Macrotrends' quarterly series. Its 52-week range is $134.80–$296.44.

Who it touches

• Rival genset makers — Cummins and Caterpillar sell into the same data-centre backup slot. A hyperscaler naming one long-term supplier is a share-of-wallet question for the rest.
• The rest of the electrical room — switchgear, UPS and cooling suppliers such as Vertiv sit beside the generator. Backup capacity ordered now implies the rest of that chain is being ordered too.
• Indian power-equipment names — Kirloskar Oil Engines, Cummins India and CG Power sell gensets and data-centre electricals at home. No rupee of this deal reaches them, but it is a hard number on how much backup power an AI build actually buys. More movers on the MarketChacha movers page.

What to watch

The one thing that flips this: $8 billion is a ceiling on a vesting schedule, not a purchase order. Only $2.4 billion of deliveries is described as expected, and portions of both the warrant and the transaction agreement were filed redacted under Item 601(b)(10)(iv), so their commercial terms aren't public. If Amazon's build slows, the later tranches never vest and that revenue never arrives. Generac's next quarterly report is the first place the $2.4 billion should surface as backlog or guidance — dated events sit on the MarketChacha calendar.

As of 5:50 am ET / 3:20 pm IST, 17 Sep 2026. Sources: Generac 8-K (SEC), Generac FY2025 results, Bloomberg, StockAnalysis, Macrotrends. For discussion and education only — not investment advice. Verify before acting.