Given the situation wineries around the region were facing earlier in the season, Ms Cooper said that was not a bad result, especially as grape quality was pleasing.
Urlar Estate owner and winemaker Angus Thomson said he was also surprised to hear that the 2012 Wairarapa vintage was larger in quantity than 2011.
"But it depends how good the reporting was the previous year."
He said grape quality at Urlar, near Gladstone, was good, especially given the cool conditions over summer.
"We escaped really, we were very lucky."
He said varieties of white wine had fared reasonably well "but it won't be a record vintage by any means. It's too early to tell with the reds, but it's likely they will be on the more elegant side".
Daniel Watson, estate manager of Craggy Range's Te Muna Vineyard, near Martinborough, said across Martinborough most producers were 15-30 per cent down in tonnage, which was a good result given the challenging early season conditions.
New Zealand Winegrowers (NZW) chairman Stuart Smith said tonnages recorded in the annual report came from information provided by grape growers themselves about how much they had harvested.
That information came from NZW's annual vintage surveys, Mr Smith said, which growers were not compelled to complete.
He said bad weather during last summer meant much of the country recorded a lower harvest than normal. Wairarapa was heavily focused on producing pinot noir, which was a crop that was often manipulated at harvest depending on quality, which could explain discrepancies in expected harvest.
Some pinot noir producers would rather not harvest at all if they thought the quality of what they produced would compromise their reputation, he said.
Palliser Estate managing director Richard Riddiford said Palliser's production for 2012 was up "slightly" on past years.
Palliser would not harvest if the quality of its crop did not meet certain quality standards, he said. "This year we were lucky to be in the position that we could, especially given what looked like a dreadful position at the end of April."