HALIFAX -- Ottawa and Nova Scotia announced an agreement in principle Monday that would allow the province to use coal-fired electrical plants beyond the new federal deadline to phase them out by 2030.

The concession is part of negotiations toward a new equivalency agreement that recognizes the work Nova Scotia has already done on greenhouse gas reductions. The province has already met Canada's target of a 30 per cent reduction in emissions from 2005 by 2030.

Nova Scotia Premier Stephen McNeil also announced during a joint news conference with federal Environment Minister Catherine McKenna in Halifax that his province would also adopt a cap and trade system for industry, with the details to be worked out by 2018.

The province opted for cap and trade after McNeil had made it clear that he wanted no part of a proposed carbon tax, saying it would be too expensive for his province's mainly rural economy.

"They (Ottawa) recognized over successive governments that we had a unique situation here in Nova Scotia," said McNeil. "We are already at the 2030 target today . . . and it doesn't mean we want to stop and we will not stop."

McKenna touted the agreement with Nova Scotia as proof the federal government is serious about moving ahead on climate change, but in a way that accommodates the concerns of the provinces and territories.

"Nova Scotia's multi-pronged approach builds on the province's existing actions and ensures that Nova Scotia will remain a leader in contributing to Canada's international target under the Paris Agreement," McKenna said.

Under the current equivalency agreement, the province must reduce greenhouse gases by 25 per cent by 2020, and 55 per cent by 2030.

Once it is finalized, the new agreement will allow Nova Scotia to find the reductions that would have been realized through reducing coal in other areas of the electricity sector. That will mean reducing 4.5 megatonnes of CO2 emissions after 2030.

The province has previously projected that coal would continue to play some part in its energy mix until 2042, although officials said there was no timetable yet for plant closures under the new agreement.

McNeil maintains that allowing Nova Scotia to use coal for a longer period than the 2030 deadline will lower costs for energy consumers.

"This allows us to transition so there's not a sticker shock on emission reduction in Nova Scotia when it comes to forcing us to build a natural gas generation plant or some other form of generation before we can transition into renewable energy," he said. "The plan in place will have Nova Scotia off coal."

Officials said Nova Scotia would create its own cap-and-trade system for polluters outside the electricity sector, but were unable to say what the economic impact of the move would be. They said a cap would be established with emitters.

Nova Scotia's dual announcements were welcomed by Stephen Thomas, the energy campaign coordinator for the Halifax-based Ecology Action Centre, although he said the yet-to-come details will be key in assessing their effectiveness.

"On the coal side I don't see that there is any announcement of increased ambition, so I'm waiting for those numbers," said Thomas.

Coal power in Alberta, Saskatchewan, New Brunswick and Nova Scotia accounts for 10 per cent of Canada's total greenhouse gas emissions.

McKenna said she would continue to work with the other Atlantic provinces, including New Brunswick, to address their concerns.

"Look, we are always looking for practical solutions, so in terms of coal there are different solutions for different provinces," she said. "New Brunswick ... Premier (Brian Gallant) is very excited about our announcement today and also very excitement about the investments that we are going to be making in infrastructure."