FRANKFURT (Reuters) - E.ON on Wednesday posted first-quarter profits that were roughly stable year-on-year, adding that investments were up by around a quarter as Europe's biggest operator of energy grids is massively ramping up spending on grids.

First-quarter adjusted core profit (EBITDA) was up 1% at 2.745 billion euros, while adjusted net profit was up 2% at 1.047 billion, the company said, confirming its outlook for the current financial year.

The group said it still expects adjusted EBITDA of 8.8 billion to 9 billion euros and adjusted net profit of 2.8 billion to 3.0 billion.

According to a poll provided by the company, analysts on average expected adjusted EBITDA of 8.9 billion euros and adjusted net profit of 2.9 billion.

(Reporting by Christoph Steitz, Editing by Rachel More)