The European Commission, the EU's executive, is expected to unveil proposed 2030 green energy goals around the year end, and Britain wants the bloc to take on an ambitious target to help limit global temperature rises to below 2 degrees Celsius.
"Meeting a 50% target is affordable ... equivalent to a reduction in the EU annual growth rate of 0.04 percent between now and 2030," said Ed Davey, speaking at U.N. climate talks in Warsaw and citing the findings of a study done by the country.
The EU's Low Carbon Roadmap, which aims to cut greenhouse gas emissions by 80-95% by 2050, says the 28-nation bloc can inexpensively achieve reductions of 40-44% by 2030.
Britain thinks the EU can attain a further 5-10% in cuts through buying international carbon offsets, effectively outsourcing the reductions to developing countries, where abatement is cheaper.
Sources have said the Commission is looking at a bloc-wide target of 35 to 45%.
A Commission analysis found a 40% cut would add around 0.5% to annual gross domestic product, in part because fossil fuel import bills would shrink.
The EU is expected to lead the way in outlining binding environment and energy targets for 2030, helping to frame a new global treaty to fight climate change.
The EU has already nearly met a target to cut 1990-level emissions by 20% by 2020, as a result of lower energy demand following a recession and a shift towards green power, such as solar and wind.
For 2030, the Commission is expected to propose targets for emissions and renewable energy, dropping an extension of its current 2020 energy savings goal.
But Poland, for instance, which is heavily reliant on carbon-intensive coal, has sought to make any further EU promises conditional on the rest of the world pledging to do more to cut emissions.