While the 27 EU countries are currently on track to achieve the 2020 renewable energy goal, many risk falling behind in the coming years without additional efforts, the European Commission said.
"There are reasons for concern about future progress: the transposition of the directive has been slower than wished, also due to the current economic crisis in Europe," the Commission said in a statement.
The warning came as the Commission issued a Green Paper that sketches out new 2030 targets for cutting greenhouse gas emissions and using clean energy, designed to keep the EU at the forefront of global efforts to combat climate change.
The bloc currently has three 2020 climate policy goals: to cut carbon emissions by 20% compared with 1990 levels, increase renewables to 20% and improve energy savings by 20%.
It is currently on course to meet the first two targets - which are legally binding - but not the non-binding energy efficiency goal.
Green Paper on energy
The Commission's Green Paper launches a public consultation that marks the first step towards creating a 2030 framework for EU climate change and energy policies.
The EU executive also published today its communication on the future of carbon capture and storage (CCS) in Europe.
"We need to define our climate and energy policy framework for 2030 as soon as possible to ensure proper investment that will give us sustainable growth, affordable competitive energy prices and greater energy security," Energy Commissioner Günther Oettinger said in a statement.
"The new framework must take into account the consequences of the economic crisis, but it must also be ambitious enough to meet the necessary long-term goal of cutting emissions 80-95% by 2050," he said.
Connie Hedegaard, the commissioner for Climate Action, said mapping out setting the stage for "a low-carbon society for 2050" would boost the economy.
"The sooner we do that, the more certainty we get to our companies and our investors," she said in announcing the Green Paper. "And the more ambitious these targets are, the better for the climate.''