The ESB Group has reported an operating profit of €455m for the year to the end of December, amid challenging market conditions.

The company, which has 3.1 million customers, also said it had invested €1.2 billion in long term electricity infrastructure during the year.

The ESB was forced to take a €140m exceptional non-cash impairment charge on generation assets during the year.

But it said that 2018 saw the delivery of a "satisfactory underlying financial performance" as it transitions to a low carbon energy future.

In its results statement, ESB said that a number of major storms had a serious impact on the network and its customers during the year. 

It said that Storm Ali in particular, at a time when most trees were still in leaf, resulted in significant levels of network damage from falling trees.

This required an "enormous" restoration response from ESB Networks and NIE Networks crews to restore power to almost 320,000 homes and businesses and make the network safe again, it added.

ESB said it had declared a dividend of €35m in respect of 2018, with total dividends paid to the Exchequer over the past ten years amounting to €1.4 billion.

"ESB continued to focus on delivering long term value and investing in critical long term electricity infrastructure for the benefit of our customers, shareholders and the wider Irish economy," the company's chief financial officer Pat Fenlon said. 

"ESB's diversified businesses and solid financial position ensure it is well placed to meet the challenges that lie ahead and remain at the forefront of the energy sector in an all-islands market," he added.