NEW YORK: Policymakers should not forget the reliability of the North American power system when designing rules to combat global warming, the group responsible for the reliability of the US and Canadian electric systems said in a report Tuesday.

Climate change initiatives will alter the way energy is used in North America. To keep the grid reliable, the industry needs time to develop and implement technologies needed to respond to those changes, the North American Electric Reliability Corp said in the report.

Although policymakers are still developing carbon-reduction legislation and regulations, NERC based its analysis on the proposed initiatives, like the Waxman-Markey bill and agreements between the United States and Canada over the Copenhagen climate talks.

The Waxman-Markey bill, which passed the US House of Representatives in 2009, requires emissions reductions below the 2005 base-year level by 3 percent by 2012, 17 percent by 2020, 42 percent by 2030 and 83 percent by 2050.

In addition, Canada and the United States agreed to meet 17 percent emissions reductions below the 2005 base-year level by 2020 as part of their participation in the Copenhagen Accords.

There are about a million megawatts of generation in the United States and Canada. Meeting the proposed carbon dioxide and other greenhouse gas emissions reduction targets will require a significant change in the resource mix, NERC said.

The United States currently gets about 47 percent of its power from coal, 21 percent from natural gas, 20 percent from nuclear, 6 percent from hydropower and the remainder from other sources, including renewable sources like wind and solar.

As the industry transitions from the current state to one that meets carbon reduction targets, NERC urged policymakers to be flexible.

"If the necessary resources are not operational in a timely manner, the new resource mix may affect reliability or require moderation of aggressive climate change goals," NERC said.

Under the proposed global warming initiatives, NERC projected a large number of coal plants would have to retire between 2020 and 2030.

That could challenge reliability in some regions, like the Midwest, that rely on coal for most of their generation, unless the retired capacity is replaced with low-carbon emitting generation like natural gas-fired plants.

From 2030 to 2050, however, even those low-carbon emitting resources like natural gas plants not fitted with carbon capture and sequestration technologies could be forced to retire to meet the carbon reduction targets, NERC said, requiring more non-carbon emitting sources like renewables.

But large-scale renewable projects require additional transmission facilities to move that power from usually remote areas to major metropolitan areas, NERC said.

And, relying more on wind and solar power, which generate energy only when the wind is blowing or the sun is shining, require development of large-scale technologies to store power, NERC said.