Heads of companies behind Australia's major large-scale solar projects are today taking their fight to save the Renewable Energy Target (RET) all the way to Canberra.

Business leaders from solar companies including First Solar, Fotowatio Renewable Ventures (FRV) and SunPower are heading to the nation's capital to meet with key ministers and parliamentarians.

"We'll be telling them that if the RET is slashed, the future looks grim for large-scale solar in Australia," Clean Energy Council Acting Chief Executive, Kane Thornton, said.

"Already, investment in renewable energy projects has drastically reduced, thanks to the uncertainty surrounding the RET generated by the Federal Government's Warburton review.

"If the Federal Government follows the review's recommendations, the clean energy industry will be decimated, with future large-scale solar projects the first to fall by the wayside."

FRV Country Manager Andrea Fontana said the RET had provided a firm regulatory basis for the more than $70 million his European-based company had pumped into Australian projects.

"We are making a highly capitalised investment, so we are only able to commit our funding and resources when we have confidence in the local regulatory framework," Mr Fontana said.

"Large-scale solar is a very reliable product - but as soon as we lose certainty on the RET, then other parts of the world will be chosen over Australia when it comes to investment."

First Solar Vice President Business Development, Jack Curtis, said when building large-scale solar projects, his company used local suppliers as much as possible, ensuring maximum investment went direct into the Australia economy.

"We focus on those countries that have a stable policy environment supporting renewable energy. If the RET is cut, it will significantly impact decisions on our current and future investment in Australia."

According to Wilf Johnston from SunPower Australia, the RET has been and will continue to be crucial to get large-scale solar projects up and running.

"Investors in utility-scale solar projects need to feel the funds they are committing are secure before they will come on board. Since its introduction in 2001, the RET has provided that security for developers. Without it, it will be much harder for them to decide to support Australian projects," Mr Johnston said.