US can save $100 bln if EPA flexible on power plant rules-study

* EPA regs could cost economy $275 bln in 2010-2035

* EPRI wants a couple more years to comply with rules

* Cheap natgas could cause 100 GW of coal retirements

Oct 5 (Reuters) - The U.S. electric power industry'sresearch arm released a study on Friday saying power companiescould save the economy about $100 billion between 2010 and 2035if U.S. pollution rules were more flexible.

The Electric Power Research Institute (EPRI) estimated itwould cost the U.S. economy up to $275 billion to meet currentand pending U.S. Environmental Protection Agency (EPA)regulations from 2010-2035 if the current timeline is followed.

The study released Friday was an update of a study issued inMay.

The EPA wants electric companies to reduce power plantemissions, reduce the amount of water used to cool generatingfacilities and regulate the handling and storage of coal ash.

EPRI said its proposed "flexible path" would reduce costswhile achieving the same level of compliance.

Under the current course, EPRI said as little as 203gigawatts (GW) of existing coal-fired capacity would remainfinancially viable, with up to 61 GW retired or converted toburn other fuels.

In EPRI's "flexible" alternative, 288 GW of coal generationwould remain financially viable with only 36 GW retiring orconverted to burn other fuels.

The United States has about 1,039 GW of generating capacity,including about 317 GW fueled by coal. A gigawatt represents1,000 megawatts. One megawatt is enough power for about 1,000homes.

Power generators have already said they would plan to shutmore than 30 GW of coal-fired generation between 2012 and 2016,EPRI said citing federal data. See Reuters factbox on coal unitsto retire or convert to other fuels

EPA regulations require controls be in place to reducemercury by about 2015, sulfur dioxide by about 2015, nitrogenoxide by about 2018 and cooling water intake by about 2018.

Under EPRI's flexible approach, the utilities would get acouple more years to reduce the emissions.

Separately, EPRI said its study was very sensitive tonatural gas prices.

If natural gas prices average $6.50 per million Britishthermal units (mmBtu) from 2010-2035 as the U.S. EnergyInformation Administration (EIA) has forecast, EPRI estimatedabout 55 GW of coal capacity could retire or convert to otherfuels.

But if natural gas prices average $8.50 per mmBtu from2010-2035, EPRI forecast just 30 GW of coal could retire orconvert.

And at an average natural gas price of $4.50 per mmBtu overthat time, EPRI forecast over 100 GW of coal could retire orconvert.

Over the past decade, natural gas has traded in a wide rangefrom less than $2 per mmBtu to more than $15, averaging about$6. The current spot cost is $3.40.

The biggest coal fired generating companies in the UnitedStates include units of American Electric Power Co

, DukeEnergy Corp, Southern Co, Xcel Energy Inc, GenOn Energy Incand FirstEnergy Corp.

(Reporting By Scott DiSavino;editing by Sofina Mirza-Reid)

((scott.disavino@thomsonreuters.com)(+1 646 223-6072)(ReutersMessaging: scott.disavino.thomsonreuters.com@reuters.net))