The boom in data center construction is lifting the outlook — and stock prices — for Waukesha-based Generac.

Generac’s sales of industrial-scale generators have been rising based on demand from data centers and its stock price has more than doubled since the start of the year. The company is expanding in Wisconsin, with plans to open a new factory to meet growing demand.

On Tuesday, Generac announced that it signed an agreement with a “leading hyperscale data center operator” to supply backup generators. The company says it landed the agreement after a “rigorous qualification process” that included factory visits, performance reviews and audits.