Scotland is on course to meet its ambitious green energy targets, it was claimed yesterday, after new figures showed around 35% of Scotland's electricity was generated from renewable sources last year.

That surpasses the Scottish Government's own target of 31% and represents almost 40% of the total UK renewable energy generation for 2011.

But critics questioned whether the Scottish Government's goal of generating the equivalent of 100% of the nation's electricity needs from renewables by 2020 was worth the huge amount of investment needed.

Statistics published by the UK Department of Energy and Climate Change presented the amount of renewable electricity being generated from the likes of wind and hydro power in Scotland in 2011, as a record high at 13,750 Gigawatt hours (GWh), an increase 44.5% on 2010.

The most controversial power source is wind generation, which in 2011 was at a record high of 7049 GWh – up 45% on 2010 and more than double the 2007 level.

Hydro generation was also the best ever in 2011 at 5310 GWh – a 62.6% increase on 2010, when output was reduced due to low rainfall. But it was also up 8.9% on 2009, the previous best year.

Energy Minister Fergus Ewing said: "Scotland met almost 40% of the UK's renewables output in 2011, demonstrating how much the rest of the UK needs our energy. We are seeing progress towards our goal of generating the equivalent of 100% of our electricity needs from renewables by 2020."

He added projects representing £750 million of investment were turned on last year, with another £46 billion-worth in the pipeline.

Niall Stuart, chief executive of Scottish Renewables, said it was "a fantastic achievement for our industry and for Scotland".

He added: "When the interim target of 31% was set, it was seen as ambitious but yet again the renewables sector in Scotland has grown further and faster than predicted, achieving 35%. That's why we are confident we can meet the 2020 target."

Stan Blackley, chief executive of Friends of the Earth Scotland, wanted ministers to be even more ambitious, saying: "Our research has shown that, with some modest investment in energy efficiency and demand reduction, Scotland could produce 130% of its electricity demand from renewable sources by 2020 and 180% by 2030. In doing so we could ensure a reliable supply of clean electricity and phase out Scotland's thermal power stations."

But Labour's UK Shadow Energy Minister, Tom Greatrex, said: "These figures highlight the need for a balanced energy mix which harnesses the resources available across the whole of Britain."

Renewables still only made up a small proportion of energy generation, he said, much less than coal, gas and nuclear. In addition the cost of the investment needed to realise this potential was borne by consumers across Britain.

Helen McDade, head of policy at the wild land charity the John Muir Trust, said the rise in green energy output was due to an increase in the number of wind farms. She added: "It's like Tesco comparing the gross turnover of one year from 100 shops with the gross turnover of 150 shops the next year. Critically, though, how much were greenhouse gas emissions reduced?"