Infratil subsidiary Z Energy says the switch from one of the world's biggest brands, Shell, to a local brand is working for the company even though its profit fell towards the lower end of guidance.

Earnings for the past year increased $10 million to $177 million but its net profit after tax fell from $203 million to $77 million after a $121 million revaluation of the company's assets.

Z chief executive Mike Bennetts said the performance highlighted the resilience and momentum in the business to manage volatility.

Margins on fuel sales were under pressure and in the last quarter refining margins were the lowest they have been since Infratil bought the business.


"Our brand tracking shows Z is already a strong preference for Kiwis, with respondents more likely to recommend Z than any competitor," Bennetts said.

Bennetts said with 91 octane fuel consistently above $2 a litre, continued public scrutiny on fuel prices was to be expected.