The green energy market is fast becoming the latest to fall victim to the precipitous fall in global oil prices, as investors shun eco-friendly tech companies.
The price of benchmark Brent crude has fallen 46 percent since June on the back of a glut in global supply and waning demand, and has put pressure both the oil and commodity sectors.
Now, green energy firms are also suffering, as investors see the lower oil price as a disincentive to invest in greener technology – or so-called "cleantech."
Danish wind turbine manufacturer, Vestas Wind Systems, has seen its share price slump almost 30 percent since June when oil prices started to fall from a high of $114 a barrel. Brent is currently trading around $60 a barrel.
Shares of one of the largest solar companies in the world, German company Solarworld, meanwhile, have slipped 26 percent since mid-June.
Boston-based investor Rob Day told CNBC that investors pulled money from cleantech companies when oil prices dropped, although he argued that the world will have to turn to more renewable forms of energy sooner or later.
"When oil prices fall like this, it tends to prompt a pullback in dollars flowing into even electricity-focused solutions, whether that makes sense or not," Day, a partner with Black Coral Capital -- a venture capital firm focused on companies in the clean technology and renewable energy sector -- told CNBC in an email Friday.
"So it's eye-rolling, but still not a surprise to see solar stock prices fall in this market situation."
Day added that low oil prices would likely, "keep some private sector dollars on the sidelines as well, and that's not good news for those who want to see accelerated rollout of such technologies."
European firms are not alone in feeling the pain of lower oil prices. U.S. electric-car maker Tesla Motors has seen volatile share price moves is trading lower by 12 percent since June.
The company was dealt a further blow last week when Morgan Stanley analysts published a note saying that low oil prices could lead to a 40 percent cut the company's sales forecast. It currently hopes to sell 300,000 cars by 2020.
It marks a turnaround from when eco-friendly energy stocks looked attractive on the back of European government subsidies for green energy investments. They were also helped by international pledges from the likes of China, the U.S. and Europe to reduce carbon emissions.
The former two superpowers – and largest emitters of carbon - agreed in November to cut total emissions by more than a quarter by 2025, and European leaders reached a deal in October to cut greenhouse gas emissions by 40 percent by 2030.
Day stressed that a global shift was taking place, with interest turning towards electricity-focused solutions, at least in the world's largest economies, which should not be hit too hard by falling prices.
"Solar in particular, but also energy efficiency, and other renewable power generation should not be significantly affected by oil prices one way or the other," he said. "If anything, more disposable income (from lower gasoline prices) could result in even faster adoption of rooftop solar and home energy efficiency improvements. That said, generalist investors don't seem to instinctively grasp this basic fact."
Those that are heavily invested in green technologies are worried that the oil rout could continue, particularly since a number of major oil producers – such as the Organization of Petroleum-Exporting Countries (OPEC) – show no sign of decreasing production in the near future.
Heavyweight businessman Richard Branson criticized OPEC for deciding not to cut oil production when it met in November, saying that the lead member Saudi Arabia was trying to undermine the green energy business.
"They have done it before and it hurt," Branson told The Guardian, which reported that he had invested £300 million ($469 million) in clean-tech. "They don't just want to damage the U.S. fracking industry, but also the clean energy business. The collapse of oil prices is going to make it much more difficult for clean energy."
The billionaire argued that before the oil price collapsed, solar energy was "actually cheaper".
"If oil goes down to $30-$40 a barrel, then it will make it much harder for clean energy," he said. "Governments are going to have to think hard how to adapt to low oil prices."
Not everyone is so pessimistic about the prospects for renewable energy, however. Martin Schoenberg, head of policy at the Climate Change Capital think tank, told CNBC on Thursday that government determination to reduce carbon emissions would, ultimately, support the renewable energy industry.
"We expect that European carbon emission targets will continue to drive investment into renewables," he said.