SCOTTISH Power's renewable energy division has posted a big increase in first quarter earnings, which the company said showed the hefty investment it has made in offshore wind power is paying off.

Glasgow-based Scottish Power said its UK renewables arm achieved €149.1m (£107m) earnings before interest, tax depreciation and amortisation (EBITDA) in the first three months, up 61 per cent on the €92.7m achieved in the same period of 2014.

Production increased by 15 per cent annually, to 1,249 megawatt hours.

Scottish Power, owned by Iberdrola of Spain, highlighted the contribution made by the £1.6 billion West of Duddon Sands windfarm offshore Barrow in Furness. This was completed in October.

The 389MW facility generated 55.8 per cent of the theoretical maximum it was capable of. Scottish Power said this was significantly ahead of expectations and comparable to or better than most UK fossil fuel generation.

Keith Anderson, ScottishPower chief corporate officer, said: "Offshore wind is now coming into its own with the power produced from the new windfarm at West of Duddon Sands ahead of expectations in the first quarter of this year."

He added: "This shows the potential of offshore wind now that we are able to use larger turbines and better technology, which we will advance further with other new offshore projects."

By contrast, ScottishPower's onshore windfarm fleet delivered 32.8 per cent of the theoretical maximum power.

Earnings from conventional power generation and sales of power to customers increased by six per cent annually, in sterling terms, to £173.5m from £163.5m.

The number of electricity customers fell to 3.3 million in the first quarter, from 3.4m in the same period last year.

Gas customer numbers head steady at 2.2m. Demand for gas increased by 8.2 per cent annually amid cold weather conditions.

Scottish Power's networks business increased earnings by 23 per cent to €309.8m, from €252.5m. Iberdrola said it is realising the benefits of a multi-billion pound investment programme in networks upgrades.

The company said it expects to invest a record £1.3bn in the UK in 2015, with most going into upgrades of power transmission and distribution networks in Scotland, north west England and north Wales.

The group, which also has operations in the Americas, increased EBITDA by around nine per cent in the first quarter to €2.14billion, against €1.96 billion in the same period last year. It said growth reflected strong operational improvements in networks and renewables and a boost from the weakening of the euro.