The Court of Appeal acknowledged that the case had been difficult because the wording of the Equal Pay Act was very poor.
Terranova argued before Justices Patrick O'Regan, Lynton Stevens and Christine French that if the court were to uphold the Employment Court decision it would lead to unworkable scenarios for employers.
Terranova said individual employers would "shoulder the burden of rectifying society-wide structural discrimination."
It would be beyond employers' expertise and resources to establish the wages of other workers, especially those on individual agreements rather than collective agreements, Terranova said.
The company also argued the wording of the Act supported the interpretation that it was the rates of pay the employer paid to its employees that was relevant in determining whether equal pay was achieved.
Health Minister Jonathan Coleman said he would wait to get further advice on the decision before commenting in full.
He said there may well be cost implications for the Government, but he had not yet been advised as to what those would be.
Asked about the Aged Care Association's concerns about the ability to cover higher wages without more Government funding, he said about $1 billion a year already went into the sector -- including funding boosts of $250 million over the past six years.
"It would be great to pay workers more but the issue at the end of the day is there's so much money that goes in there from the Government. And there's a lot of money that's gone in there.
"The issue is really that providers get to decide how to spend it and that's the decision they make."
- additional reporting: Claire Trevett of the New Zealand Herald