FRANKFURT/GDANSK (Reuters) - European companies focused on clean energy are abandoning expansion plans, bracing for lower sales or see funding of U.S projects in doubt because of fears over what a potential election victory for Donald Trump could mean for their sector.

Trump has dismissed President Joe Biden's policies to fight climate change as a "green new scam" and is expected to try to undo much of his administration's work, including the Inflation Reduction Act (IRA) that offers tax breaks and subsidies to U.S. and foreign companies investing in sustainable energy.

The law passed in 2022 has acted as a powerful incentive for European companies from the sector to expand or establish their U.S. presence, but a spectre of a second Trump presidency is giving them a pause.

"With a Donald Trump who A) is very opportunistic, B) is also very polemic and C) is also fairly unpredictable, you have to ask yourself whether it makes sense to make such a bet," Peter Roessner, chief executive of Luxembourg-based hydrogen firm H2Apex, told Reuters.

Under the IRA, the company could have built a hydrogen tank production plant in the United States for around a third of the $15 million in costs. In February, however, Roessner decided to cancel the plan over concerns that Trump could be reelected even though the company already had held initial talks with potential customers.

Market bets that Trump would win back the White House in November have intensified this month after he was shot at during an election rally and days later secured the Republican Party nomination.

Recent polls show a narrowing gap between Trump and Kamala Harris, the likely Democratic candidate with similar views on climate to Biden's. Yet Roessner's comments reflect anxiety among Europe's clean tech firms over what a Trump presidency could mean and how they are trying to prepare for such a scenario.

Wood Mackenzie energy data and analytics company reckons it would put a projected $1 trillion in low-carbon energy investments at risk by 2050.

Consultancy Roland Berger said that while a full repeal of the IRA was improbable, a Trump administration could still jeopardise incentives for electric vehicles, EV charging, solar power and energy efficiency.

German solar firm SMA Solar issued a profit warning last month, citing a possible government change in the United States, the world's second-largest solar market after China, as one of the risk factors.

The world's largest maker of solar inverters initially aimed to choose a location for a planned factory in the United States by the end of June, but is yet to find one, saying it is still evaluating possible sites in a number of states.

'BOARDROOM HEADACHES'

While SMA is not abandoning its expansion plans for now, the company told Reuters on July 4 that it "is observing that the unclear outcome of the presidential elections in the USA is currently leading to a certain reluctance to invest in renewable energies locally."

That hesitation is reflected in the performance of clean tech shares, with the RENIXX index, which tracks the world's 30 biggest renewable firms, underperforming global stocks since the assassination attempt.

Orsted, the world's largest offshore wind farm developer, has been hit particularly hard after Trump said in May he would target the sector on his first day in office if he got reelected. Orsted declined to comment.

Some renewable energy companies appear undeterred by the uncertainty.

German wind turbine maker Nordex, for example, last month said it would resume production at a mothballed plant in Iowa, saying the U.S. would remain an important and sufficiently big market in the future "regardless of political developments".

Several others, however, report delays as prospective partners expected to co-fund projects hold off with their commitments.

Hydrogen firm Thyssenkrupp Nucera has spoken of delays to final investment decisions concerning U.S. projects, a factor that drove an outlook cut at its alkaline water electrolysis unit earlier this year.

The company said while it continued to focus on the U.S., it was vital how the IRA programme would look like after the election. It said strategic investors with a long-term focus on the cleantech sector were likely to resume projects earlier in the face of continuing uncertainty than those who are more opportunistic.

Norwegian rival Nel said it was yet to make an final investment decision for a planned production facility in Michigan, which was contingent on the demand for its products in the U.S. market.

The uncertainly over the U.S. election outcome and its impact is starting to affect industries beyond the clean tech sector. For example, German machinery firm Trumpf reported earlier this month a 12% drop in U.S. sales for its 2023/24 fiscal year, blaming "geopolitical uncertainties" that made industrial customers cautious.

This growing complexity companies have to navigate globally can create "analysis paralysis" when it comes to investment decisions, said Marcus Berret, global managing director at Roland Berger.

"Boardroom headaches have increased considerably as a result."

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