AGL Energy Ltd, Australia's largest energy retailer, has had its credit rating outlook upgraded to stable after the completion of an asset sale program.

Ratings agency Standard & Poor's Ratings Services has affirmed AGL's `BBB' long-term credit rating, and revised the rating outlook to stable from negative.

Standard & Poor's said the revision reflected AGL's improved balance-sheet and the company's stated strategy that it would pursue growth opportunities without putting its credit quality at risk.

"AGL has represented that it will cautiously undertake its growth strategy and focus on improving its portfolio of energy assets and vertical integration with its existing operating markets," Standard & Poor's credit analyst Tammy Garay said in a statement.

Ms Garay said any upgrade to the AGL rating was unlikely over the next couple of years given the group's challenging near-term operating environment.

AGL has completed asset sales totalling more than $3.2 billion over the past 12 months, including the sale of its shareholding in Queensland Gas Company Ltd.

Shares in the company had dipped 25 cents, or 1.74 per cent, to $14.08 by 1202 AEDT on Friday.

"In our view, BBB is the appropriate long-term credit rating to maintain for AGL's business profile and to support execution of our integrated renewable energy company strategy," AGL chief financial officer Stephen Mikkelsen said in a statement.