Martin Howley of Sustainable Energy Ireland (SEI) told the Sunday Tribune that the exaggerated impression of the government's commitment to green energy was down to the complexities of the statistcs involved.

"It's a good target - when put in context, " Howley said.

However, government critics were quick to label the government's statistical sleight-of-hand "greenwashing".

"The government is trying to mislead people, " said Green Party energy spokesman Eamon Ryan.

When Dempsey announced the government's targets for green energy last Monday, critics derided his goal of deriving one-third of consumed electricity from renewable sources by 2020 as unachievable.

But an explanation of the figures by the head of SEI's energy-policy statistical-support unit exposes the government's objective as quite modest, as the 33% quoted in the White Paper on energy actually equates to less than six percent of total projected energy generation.

Moreover, only about 2.5% of Ireland's current energy consumption is sourced in renewables, according to SEI figures from 2005, the most recent available.

Howley said significant differences in energy input and electricity output, as well as electricity's share of total energy use, accounted for the disparity between the figures.

Howley explained that because electricity production is not particularly energy efficient - some gets lost as heat or in transmission - typically only about 40% of the energy input actually becomes consumable electricity on the other end.

Moreover, because electricity accounts for about a third of all energy used in Ireland - transportation and heat account for the other two-thirds - that figure gets divided by three to determine where it fits in the total energy picture.

Of the consumable 40% of total electricity generated from all sources, which itself is about one-third of all energy generated, only a third of that - or 5.67% - is the number for the share of green electricity consumption compared to total energy inputs.

"In effect the electricity end-use will be 17% [of total energy generated], " Howley said.

"The contribution of renewables will be a little less than six percent of overall consumption. It's a good target - when put in context."

The government has announced parallel ambitions of 12% renewable heat market penetration and 10% biofuels penetration by 2020, which together would account for roughly the same amount of energy generation from renewables as the green electricity targets would.

That means the government is aiming for 12%-13% of total energy from renewables by 2020.

In comparison, EU policy also targets an increase in the contribution of renewables to 12% of total energy by 2010, according to SEI documents.