HOUSTON, April 2 (Reuters) - The U.S. has doubled the

pace of cutting carbon emissions since President Joe Biden's

Inflation Reduction Act (IRA) passed in 2022, analysts and

scientists said, with more than 80 solar, wind and energy

storage projects taking advantage of the law's mix of direct

payments and tax credits.

The IRA and the Bipartisan Infrastructure Law last year

provided $239 billion for clean energy, electric vehicles (EVs),

electrification of buildings, and carbon management in the U.S.,

up 38% from 2022, according to the Clean Investment Monitor, a

joint project of the policy researcher Rhodium Group and MIT.

Still, experts said there is a long way to go before the law can

achieve Biden's wider climate ambitions of net-zero by 2050.

Ultimately, analysts expect U.S. government direct spending

and tax credits under the law will far exceed the initial $400

billion estimate. Goldman Sachs Group ( GS ) has projected up to $1.2

trillion spending through 2031.

Two years after passage of the landmark climate law, early

winners have been sectors such as electrical power, battery

manufacturing and traditional clean energies like wind and

solar. The law encouraged Asian and European companies to invest

more in the U.S., which in turn prompted Europe to develop its

own Green Industrial Plan over worries the U.S. would pull away

clean-energy projects and talent.

Still, state and local regulations have hindered development

of new transmission lines, and new EV charging stations have not

sprouted up as quickly as some had hoped. Also, the IRA has been

much slower to encourage other types of projects, especially

hydrogen, carbon sequestration, geothermal and nuclear energy,

noted Jigar Shah, head of the loan programs office at the

Department of Energy.

Those sectors "continue to struggle around figuring out how

exactly to put all the pieces together," Shah said last month at

the CERAWeek energy conference in Houston.

Oil companies have bristled at the criteria for tax credits

for hydrogen fuel plants. Exxon Mobil Corp ( XOM ) Chief

Executive Darren Woods warned in an interview that he might

scrap a multibillion-dollar plan to build the world's largest

hydrogen plant in Texas.

"The challenge has been translating the legislation of the

IRA into regulation," Woods said, noting the proposed regulation

favors hydrogen fuel from plants powered by renewable energy

rather than natural gas.

Even in sectors like electric vehicles, companies are

discovering "a host of practical barriers to putting the IRA tax

breaks to work", said Jason Bordoff, founding director of the

Center on Global Energy Policy at Columbia University.

For instance, he cited a lack of transmission lines that

would connect new clean energy projects to the grid and

local-content requirements for EVs.

Tax breaks for EV purchases under the law have U.S.

automakers worried about cheap Chinese vehicles flooding the

market, triggering rules for U.S. content and calls in

Washington for steeper tariffs. China has protested U.S. content

rules on EVs to the World Trade Organization.

Concern about Asian companies cornering the market on

advanced technology needed for EVs and other green energy items

also prompted Washington to launch aggressive investments in

semiconductor plants.

"Some parts of clean energy like electric vehicles have

become particularly politicized. There could be a risk that the

implementation of the IRA by the administration could be slowed

down," Bordoff said.

So far, a $7.5 billion U.S.-funded network of electric

vehicle charging stations has led to only a handful of stations

despite a temporary waiver of U.S. content rules.

Regulatory hurdles have hindered advancement of complex

projects favored by oil companies such as hydrogen plants or

carbon capture systems for oil wells, noted Roman Kramarchuk,

head of climate markets and policy analytics for S&P Global

Commodity Insights.

He predicted these projects would see a second wave of

development "when there is more certainty around how that

financing is supposed to happen or what it takes to get a deal

done."

Oil executives at the conference in Houston also complained

that regulations were making it difficult to build new natural

gas pipelines, which undercut efforts to remove the gas from

drilling sites.

Now, a proposed IRA-linked fee for excess methane emissions

on federal lands has raised a new hurdle, ConocoPhillips ( COP )

Chief Executive Ryan Lance said, adding that "industry is

pushing back" on that issue.

Despite the various industry complaints, the climate law has

helped the U.S. reduce carbon emissions by 4% annually, double

the pace of 2% a year before the law, nine research teams across

the U.S. said last year in an article published in the journal

Science. Still, some experts said the pace must accelerate.

"The IRA doubles the pace of reductions but should have

tripled it to hit our 2030 climate goals and get on the path to

net-zero by 2050," said Princeton Mechanical and Aerospace

Engineering professor Jesse Jenkins, one of the study

participants.