Meridian Energy, which reports earnings next Monday, was the biggest gainer in the benchmark index today, rising 4.9 per cent to $4.90. The 1.18 million shares traded was just ahead of its three-month average.
Index heavyweight A2 Milk also had a strong day with its shares rising 3.8 per cent to $16.85. Shares in its supplier Synlait Milk rose 0.5 per cent to $9.43.
Mercury NZ nudged higher, closing at $4.95, up 0.2 per cent, as the energy supplier posted an 11 per cent drop in earnings, less than forecast. Net profit was up to a record $357m from $234m, a result Williamson described as "pretty acceptable", given a difficult environment for electricity generators.
Fletcher Building shares rose 2.7 per cent to $4.57, with almost 1.1 million shares traded, close to its average. Williamson said there was a bit of bargain-hunting ahead of the construction firm's result tomorrow.
Z Energy led the market lower, falling 2.9 per cent to $6.42, on slightly higher than usual volume of 1.04 million shares after a draft report from the Commerce Commission today suggested fuel retailers may be earning close to $400m a year in excess returns, requiring changes to increase competition in wholesale fuel supply.
Spark New Zealand, also reporting earnings tomorrow, was the heaviest traded stock in the benchmark index, with 2.4 million shares traded. It fell 0.7 per cent to $4.01.
Among stocks trading on volumes of more than a million shares, Kiwi Property rose 1.2 per cent to $1.64 and Air New Zealand fell 0.7 per cent to $2.73 ahead of earnings announcements due Thursday.
Outside the main index, shares in Comvita fell 4.9 per cent to $2.71. The manuka honey-maker today deferred its annual results until later in the week, saying more time was needed to complete its audit.
"They are looking at a possible impairment on some of their assets and their auditors will be doing their work. The market gets a bit nervous when they miss their due date for results so investors will be being careful," Williamson said.