José Manuel Barroso, the Commission president, said "the member states have agreed on the 20% target [for energy efficiency] but so far they're not delivering, and the way that the process is being pursued is far from perfect".
The EU's 2020 targets are for a 20% reduction in greenhouse gas emissions, a 20% increase in the proportion of renewables in the energy supply, a minimum use of 10% biofuels and a 20% improvement in energy efficiency, all compared with 1990 levels.
However, the energy efficiency target is the only one of these that is not binding. On 15 December 2010, the European Parliament passed a motion demanding that it be made so.
Barroso declined to say whether he supported such a move but conceded that, unlike the binding renewables and emission reduction targets, "there was no specification of the concrete steps so probably this is one of the reasons why we are not going so fast in energy efficiency".
Last month, Marie Donnelly, director at the European Commission's DG Energy, told EurActiv that energy efficiency grants from a reallocated fund worth eight billion euros were still going unclaimed.
So far, she estimated, the EU had only achieved energy consumption reductions of "somewhere between nine and 11%".
But Barroso insisted that all the EU's targets were still realistic.
"That's why I'm going to discuss with member states how we can now do things which reach the 20% target by 2020 on energy efficiency," he said, "because the potential for savings in energy in transport and households, buildings and industry are really there".
Barroso on Southern Corridor tour
The Commission president also expressed confidence that the EU executive could make advances towards guaranteeing Europe's energy supply, in advance of a visit next week to Azerbaijan and Turkmenistan. But he gave no details of his main message, saying that he did not want to "prejudge" talks with the countries' relevant authorities.
Several EU states and the US have been backing for years the Nabucco pipeline project to pipe gas to Europe from countries including Azerbaijan and Turkmenistan, as a means of diversifying the continent's energy supplies. But in the meantime, several competitors to Nabucco have appeared and all these projects are now listed under the headline 'Southern Gas Corridor'.
Azerbaijan's top negotiator, Elshad Nasirov, recently said that two competing bids from the Turkey-Greece-Italy Interconnector and the Trans-Adriatic Pipeline could "turn out to be more attractive" than Nabucco.
"I'm expecting some progress [for Nabucco]," Barroso said. "I think there has been some progress. There are better prospects for Nabucco. I believe that will be a success story. Our goal is to have a clear commitment with those countries regarding the [European] Southern Gas Corridor and of course, Nabucco."
The Gazprom-led South Stream pipeline project, seen as Nabucco's strategic rival, is also making progress. Several EU countries participate both in the Nabucco and South Stream projects.