"Some member states have made progress and are in line to meet their renewable targets or have gone beyond them … while others are lagging behind," Oettinger said Monday in Brussels.
He was speaking at the release of the body's interim report on its ambitious clean energy targets -- namely boosting the share of renewables to 20 percent of the energy mix until 2020.
To reach that goal, investments need to "double over the coming years" to $96 billion a year, after around $48 billion were invested in renewables in 2009, Oettinger said.
By 2010, Brussels wanted to produce 21 percent of its power from renewables, a target it barely missed, reaching an 18 percent share, Oettinger said.
"We're on the right track but we need to step up the pace in the next 10 years," he said.
Oettinger also called for more investments into energy infrastructure and smart planning when it comes to new capacity installations. Because of different national support schemes, green power plants aren't always built where they can best produce, Oettinger said.
"To keep costs down, we should install more wind power units where the wind blows and more photovoltaic plants where the sun shines," the commissioner said, in an obvious reference to the solar power boom in his native Germany, where a generous feed-in-tariff has led to the world's largest solar power market when it comes to installed capacity.
The commission's calls for a European-wide green power support scheme, issued several times over the past weeks, have sparked fears in Germany that the domestic market could collapse after solar plants move south.
Countering the German concerns, Oettinger said he wanted to tinker with national policies as little as possible.
"But what I don't want is that European business models fail at the national borders," he said, mentioning as an example Desertec, which aims to send solar power generated in North Africa to consumers in Europe.
Oettinger said investors told him that they didn't need state or EU money to build the plants. Instead they want a guarantee to have solar power generated in Tunisia treated like solar power generated elsewhere in Europe -- that it will be integrated into the grid for a feed-in-tariff.
"And I'm convinced that the feed-in-tariff for solar power made in Tunisia would be much less than its counterpart in cooler regions in Europe," he said.
The EU in 2007 agreed to reduce greenhouse gas emissions by 20 percent, to increase the share of renewables in the energy mix to 20 percent, boost energy efficiency by 20 percent, all by 2020 compared with 1990 levels.