Lower coal prices and delays to operations have caused Whitehaven Coal to post a $47 million first half loss.

The NSW-focussed miner's result in the six months to December 31 was down from a $19.9 million profit in the previous corresponding period.

"Whitehaven's first half performance has suffered from a number of adverse impacts on the business, the most significant being weak coal prices and a strong Australian dollar," outgoing chief executive Tony Haggarty said in a statement.

The company was also impacted by a train derailment and maintenance at its Sunnyside mine.