Generac is best known for making backyard generators that rumble to life after power failures. But artificial intelligence is its new frontier. The Waukesha, Wisconsin-based company is spending $250 million by the end of next year to equip multiple factories to make beefed-up versions of its generators for data centers. The order backlog for those machines already stands at $1.6 billion, and the company expects to add about 1,000 workers, a 10% increase in its headcount.