More than any other policy in the US, Renewable Portfolio Standards have been the most effective tool in growing the clean energy market. But not everyone is happy with its success, which has seen RPS initiatives of varying strengths applied in 29 states plus Washington DC.

Last week, legislators in Kansas voted down the latest attempt to repeal the state's RPS goal of 20% by 2020. This was no one-off assault, but a coordinated nationwide campaign orchestrated by fossil fuel advocates.

Last year, legislators in at least 19 states introduced bills that would repeal, freeze, or weaken their commitment to renewable energy, according to the National Resources Defense Council.

Ohio, Oregon and North Carolina are all in the crosshairs of this anti-RPS crusade led by the American Legislative Exchange Council (ALEC), an advocacy organisation supported by the Heartland Institute and Americans for Prosperity, which are in turn financed by the Koch Brothers, the arch enemies of clean energy.

In November, Todd Wynn, director of the Energy, Environment and Agriculture Task Force at ALEC, fired the first clear shot across the bows when he blogged: "ALEC’s model bill for state legislators, entitled the Electricity Freedom Act, repeals a state’s renewable energy mandate stating 'a renewable energy mandate is essentially a tax on consumers of electricity that forces the use of renewable energy sources beyond what would be called for by real market forces and under conditions of real competition in generation resources'."

Wynn then went on to use data from a discredited report from the Beacon Hill Institute, which according to Gabriel Elsner from the Checks and Balances Project, has received funding from Koch Industries.

"These flawed reports are being used in many states to try to roll back these RPS laws," he said. "They're publishing these step and repeat studies that use flawed data to inflate the costs of clean energy and claim that RPS bills are bad for the state.

"The clean energy industry is growing so rapidly that the fossil fuel interests do see it as a competitive threat. What we're seeing play out is this new industry that has enormous potential fighting for economic policies and public policy that can help grow the industry in the states."

Jeffery Wolfe, founder of GroSolar, said that although an RPS had yet to be repealed, it was having the desired effect of creating enough market uncertainty to spook investors.

"In Vermont they are trying to create very significant regulatory hurdles that would make it more or less impossible to permit a wind project or a large solar project,” Wolfe said.

"It's not just a concern, it's a growing reality in the solar industry. This is very much part of a targeted campaign to quash all renewables because we're now becoming significant generation sources and are threatening their incomes.

"ALEC isn't fighting to modify, they're fighting to do something that seems very innocuous but they want to kill the industry. They're not fighting to reduce; they're fighting to kill."

He said that their state-by-state strategy was difficult for a small industry like solar to defend and would distract efforts to move legislation forward.

"This takes all of our resources to defend; rather than move the legislature forward, we're defending our position. That's also negative to the industry.

Until a strategy is worked out, Wolfe reckons that the truth is solar's best ally.

"We operate well in the sunshine, by exposing what's going on. It's sometimes easier to peddle the truth than what these folks are peddling. So we're a little bit more successful because we have the truth on our side, but it is a big fight and we're enlisting true grassroots rather than fake grassroots groups.

In North Carolina, the fight against its modest 12.5% RPS target continues, led by Mike Hagel, a Duke Energy employee turned legislator.

Betsy McCorkle, director of government affairs at the North Carolina Sustainable Energy Association, said that despite the belt-tightening public spending rhetoric, Hagel's strategy was transparently anti-renewables.

"The bill sponsor’s claim that this is an unfair subsidy to the renewable industry and North Carolina doesn't need to pick winners and losers," she said. "North Carolina's RPS was part of a very comprehensive piece of energy legislation that was passed in 2007. Senate Bill 3 also included favourable provisions for nuclear, coal and natural gas, so our argument is that if you just pull out the renewable energy standard, you would be picking winners and losers."

McCorkle said that she too had started to observe market uncertainty as investors and project developers sit tight for a final legislative win or loss.

"It's caused a lot of uncertainty, because the bill says that the utilities can recover costs from contracts up to July 2013; they are nervous about working on any new deals because there's the possibility that the bill will pass and utilities are very risk averse and they wouldn't be able to recover those costs.

"It's making investors nervous and utilities nervous even though the bill hasn't passed, it's still having a very negative affect on the certainty element for business owners and that's the worst thing you can do in a down economy is make things more uncertain that they already are."

Hagel's bill is unlikely to get very far. North Carolina's RPS is popular and has helped to bring $1.7 billion in investment, and created more than 21,000 temporary and permanent jobs, according to the NC Sustainable Energy Association.

But apart from deplete resources that should be spent on positive policy advocacy rather than defending solar's position, the attack on RPS, though bloody, is not expected to take too many casualties.

"What happened in Kansas was that this ideology and political rhetoric from fossil fuel funded front groups lost out to the economic reality that clean energy industry is creating jobs and economic opportunities," said Elsner. "Hopefully, we'll see similar efforts in places like Ohio and North Carolina that also have these clean energy companies and economic opportunities as a result of clean energy policies."