(Adds details on expected loss on disposal, Perth Energy comment)
Aug 8 (Reuters) - Utilities investor Infratil IFT.NZ said on Thursday it would sell its 80% stake in Perth Energy at a discount to Australia's biggest power producer AGL Energy AGL.AX for A$55 million ($37.17 million) after starting a review last year.
The deal is expected to lead to a loss on disposal of NZ$33 million ($21.26 million), Infratil said in a statement.
"We are disappointed to realise a loss on sale," Perth Energy Chairman Roger Crawford said.
Perth Energy is among the top electricity retailers in Western Australia and its acquisition would bolster AGL's footprint in the region.
AGL was not immediately available for a comment.
"This sale enables the Perth Energy business to continue to grow under AGL's ownership and allows Infratil to focus its investments on established platforms," Perth Energy's Crawford said.
Infratil said it may get further proceeds of A$14.9 million in cash within three years based on meeting certain criteria.
($1 = 1.5521 New Zealand dollars)