The NSW premier reversed the previous government's decision to illuminate the Opera House for the coronation on Saturday, saying he wanted to "protect taxpayer money".
The government was looking to formalise how decisions were made about when the sails of the Opera House were lit up, the premier told reporters on Monday.
The hefty $80,000-$100,000 cost was significant and the sails were being lit too often, he said.
The sails were illuminated for 23 days in 2012 but that ballooned to more than 70 days last year, costing taxpayers up to $7 million annually.
The requests to government were also increasing, the premier said.
"It was for a whole range of events, trivial matters, from visiting soccer teams to important heroic events for the state, which I think are important to commemorate on the side of the Opera House."
The government had already rejected a number of requests since coming to office to light up the Opera House from various organisations and for religious events.
"The government hasn't only rejected this particular advice in relation to the King's coronation," Mr Minns said.
"I do believe it's important to protect taxpayer money. And frankly, I think it was just being laid out too often."
The Australian Monarchist League condemned the decision not to light the sails for the King.
"Had the premier contacted the Australian Monarchist League, our members would readily have contributed towards the funding for this purpose on this important occasion," the statement said.
"From now on, should taxpayer funds ever be used to light up buildings, it will prove that this decision was based on Mr Minn's republican sympathies and not on cost," it said.
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