The EU Tracking Roadmap from the Keep on Track monitoring body warned that 14 states are expected to fall short of their targets, with another four states hanging in the balance.
This is despite 22 states hitting the interim targets for 2011/2012, indicating a slowing in progress.
The report found that the main barriers came in the form of a lack of reliable renewable energy support scheme, a dearth of access to sufficient finance, and the low remuneration level of existing support schemes.
Despite having the greatest wind energy deployment in Europe, Germany is flagged up as one of the states whose ability to hit the target is in doubt. Recent changes to the country's support structure "massively threaten" the future of renewable energy development, the report found.
Perhaps surprisingly, Italy is classed as on track to hit its target in spite of a fall off renewable energy installations in recent years.
Reforms in Spain that retroactively removed support for renewable energy developments are highlighted as the key factor in the country's expected failure to meet its target.
These shortfalls by member states are projected to result in a 17.9% renewable energy share for the whole of the EU in 2020, below the 20% target. However, the report also adds that a change in policy in individual member states could still result in a 21% deployment.
While no specific sanctions are attached to missing the target, any member state doing so would be likely to find itself in front of the European Court of Justice, which could impose a financial penalty.
The states that are expected to hit their targets are Austria, Bulgaria, Cyprus, Denmark, Estonia, Italy, Latvia, Romania and Sweden. There is uncertainty relating to Germany, Finland, Ireland and Slovakia.
It is expected that Belgium, the Czech Republic, Spain, France, Greece, Hungary, Luxembourg, Latvia, Malta, the Netherlands, Poland, Portugal, Slovenia and the UK will not meet their 2020 targets.