The head of Adelaide Zoo believes it's been well worthwhile spending millions to become the only southern hemisphere zoo to have pandas.

That's even though the zoo got into financial trouble just two years later.

The issue of pandas being brought to Wellington Zoo has quickly gathered momentum, as the Wellington City Council assesses the business case for it.

Adelaide got two pandas in November 2009, and immediately saw annual visitor numbers go from 350 thousand to 500 thousand.

CEO Elaine Bensted said the numbers peaked for around 18 months, during which time people had to book in a time to see the pandas, because they were so popular.

Ms Bensted said visitor numbers have now settled down to just over 400 thousand a year.

She said they spent nearly 10 million New Zealand dollars building their panda enclosure - which is the same figure quoted as an initial estimate for Wellington.

However, Adelaide's upgrade included additional work on an entertainment and function area.

It also spent money on an air conditioning unit so the pandas wouldn't have to endure Adelaide's 45 degree summer heat - a problem Wellington wouldn't face.

Ms Bensted said the Australian government pitched in for the cost, and continued to contribute funds.

"[They] provide payment to China on a yearly basis for giant panda research".

Adelaide Zoo reportedly also needed a government bail out after falling into debt of almost 27 million dollars in 2011.

John Key has said he's open to putting some money towards Wellington's pandas, but it "wouldn't be a lot".

Aside from money troubles, Elaine Bensted says pandas gives the Adelaide Zoo something unique and "a real point of difference".

She said their popularity could surge again if the pandas mated, which hadn't happened in the southern hemisphere before.

Ms Bensted is hopeful their female panda is pregnant at the moment, but that's to be confirmed.

There's been no suggestion Wellington's pandas would be able to breed.