The move comes amid growing pressure from Democratic politicians and activist investors for power producers to reduce their hefty contribution to climate change.
"If you're going to pursue the more aggressive carbon-reduction targets, you're going to retire coal earlier, you're going to be replacing it earlier with renewables, batteries, storage etcetera," said Duke Chief Financial Officer Steve Young in an interview.
"That pushes up the capital profile."
According to Young and an investor presentation made on Friday, Duke will boost projected capital spending by $2 billion to $58 billion for the period from 2020 to 2024, and projects a capital plan "in the range of $65 billion to $75 billion" for the following five years.
Neither the near-term spending increase, nor the longer-term projection have been previously reported.
Duke said the increased spending will cover efforts to cut greenhouse gas emissions by retiring old coal plants and replacing them with more solar and wind facilities, with the exact targets tied to forthcoming regulatory decisions.
Other power utilities have embraced similar strategies as the cost of renewable generation falls. But the outlook from Charlotte, North Carolina-based Duke, the largest regulated U.S. utility, also stands out because it has given public officials and other stakeholders a large say on how quickly to move away from fossil fuels.
Duke has outlined various fuel-mix scenarios in recent "integrated resource plans" filed to regulators in North and South Carolina, but did not make a recommendation on which to pursue.
The omission was unusual for a large utility since a faster move will require more spending, but Young said the approach should help build public support. Duke will make a similar filing in Indiana, he said.
Shares in Duke were up less than 1% at $93.61 at midday.
Chief Executive Lynn Good told investors on a webcast that Duke will add a climate goal to its executive compensation plan in 2021 "just to ensure that we are making the progress that we need to make" in areas like advocacy and public policy.
Asked about reports that Duke had rebuffed acquisition interest from NextEra Energy Inc, the world's largest generator of renewable energy, Young said "we can't comment on rumors."
In August Duke took a $1.6 billion charge for the cancellation of a natural gas pipeline.
Young said the move did not affect Duke's broader strategy but will probably lead to changes in the locations of new plants.
Duke has set a target of reaching net-zero carbon emissions by 2050. Faster technical advances would be required to meet the 2035 timeframe proposed by U.S. presidential candidate Joe Biden, Young said.
For the period through 2024, Duke's efforts should allow earnings per share to grow "at the upper end" of its current forecast of 4% to 6%, the company said.
(Reporting by Ross Kerber; Editing by Richard Valdmanis, Richard Pullin and Richard Chang)
By Ross Kerber