April 29 (Reuters) - Generac GNRC.N raised its annual sales growth forecast after reporting better-than-expected first-quarter earnings on Wednesday, helped by solid demand for backup generators and a growing backlog from data center customers.

Shares of the company rose 12% in premarket trading.

Extreme weather and ongoing grid reliability concerns led to frequent outages, boosting demand for power backup systems across residential and commercial customers.

CEO Aaron Jagdfeld said the company was gaining traction in the fast-growing data center market, nearing vendor approval with multiple hyperscale customers and expanding backlog with both new and existing clients.

In March, Generac said it is reshaping its operating structure to Residential and Commercial & Industrial divisions from a geographical framework to better reflect customer demand and internal management.

The company now expects 2026 net sales growth in the mid-to-high teens percent range, up from its prior forecast of mid-teens range, with about a 2% favorable impact from foreign currency, acquisitions and divestitures.

Sales in the company's largest segment, residential, increased by 1% in the quarter, while sales in the commercial and industrial segment rose by about 28%.

Adjusted profit per share for the quarter ended March 31 came in at $1.80, above analysts' expectations of $1.33, according to data compiled by LSEG.

Revenue for the first quarter was $1.06 billion, slightly above estimates of $1.05 billion.