(Adds details on results, background, forecast) Aug 19...

(Adds details on results, background, forecast)

Aug 19 (Reuters) - Australia's Origin Energy Ltd (ORG) said on Thursday underlying profit dropped 68% to its lowest in 16 years, as a collapse in wholesale electricity prices pummelled the power retailer's energy markets business.

It also booked impairment charges and restructuring costs totalling A$2.3 billion ($1.67 billion) during the year.

Origin, AGL Energy (AGL) and peers have been struggling with a recent flood of wind and solar power into Australia's grid that has hit prices and squeezed margins.

The Sydney-based company said underlying profit was A$318 million for the year to June 30, compared with A$1.02 billion last year. It still beat Refinitiv IBES estimates of A$275.6 million.

The company expects fiscal 2022 underlying core earnings between A$1.85 billion and A$2.15 billion, compared with A$2.05 billion in fiscal 2021.

The electricity and gas retailer had forecast a steep fall in next year's earnings for its energy markets business last month, but expects some recovery in fiscal 2023.

Origin declared a final dividend of 7.5 Australian cents per share, compared with 10 Australian cents a year earlier.

($1 = 1.3810 Australian dollars)