The company plans to invest £5.2 billion over four years to more than double its current renewables capacity. Scottish Power's parent company, Iberdrola, says it's acting to cut carbon emissions by 30 percent by 2020, and aims to be carbon neural by 2050.

Scottish Power will now produce all of its power from windfarms, including the forthcoming offshore East Anglia One, which will become the world's largest when it opens in 2020. However, while the company's five million customers will be supplied by green energy, some traditional electricity will still be brought in from other coal and gas power plant operations. Furthermore, Drax intends to use its newly-acquired infrastructure to fill the gaps in the UK energy supply when solar and wind output is low.

As such, the deal doesn't necessarily represent a significant reduction in emissions, nor does it herald any change in the volume of the UK's carbon-burning capacity -- so there's an element of greenwashing at play. Nonetheless, it's a sorely-needed show of green initiative from a major power supplier -- if the rest follow suit then the country's climate change targets will move a little closer within reach.