EDF reported higher 2011 earnings as increased nuclear output offset a drop in hydroelectric power generation and the group reiterated previous growth forecasts even taking into account the need to boost spending to improve nuclear safety.

The French utility has forecast annual average core earnings growth of 4 to 6 percent at constant exchange rates and an average annual net profit rise of between 5 and 10 percent in the period from 2011 to 2015.

Core earnings, or earnings before interest, tax, depreciation and amortisation, rose 4.7 percent to 14.82 billion euros (12.3 billion pounds) last year on sales up 2.2 percent at 65.31 billion.

Recurring net income increased 13.4 percent to 3.52 billion euros, EDF said in a statement on Thursday, despite volatile international energy markets and volatile and difficult macro-economic conditions.

In France, nuclear output in 2011 was 421.1 TWh, exceeding its raised target of 415 and 420 terawatts/hour, or TWh, on the back of strong availability from the country's nuclear generation complex which increased to 80.7 percent from 78.5 in 2010.

For this year, French nuclear output should reach 420-425 TWh, EDF said, taking into account component replacements as well as potential outages related to additional safety assessments following the nuclear disaster in Fukushima, Japan.

France's nuclear watchdog ASN said last year the country must invest billions of euros to improve the safety systems of its nuclear facilities so they can withstand the kind of extreme shocks that triggered the Fukushima disaster.

EDF has said its planned costs over the next 30 years to prolong the lifespan of 19 of its nuclear power plants from 40 to 60 years would reach the high end of an originally expected 40-50 billion euro range.

Over the past decade EDF has turned itself into a global utility with ventures in eastern Europe, the United States and the UK. But it is still highly dependent on the French market for its profits.

The future of nuclear energy in France has featured prominently in the political debates ahead of the country's presidential elections in April and May.

EDF proposed paying a dividend of 1.15 euros over 2011, unchanged from last year. For 2012 it said it would keep the dividend at least stable.

EDF is diversifying its nuclear-dominated portfolio by boosting its businesses in gas and coal, as well as hydropower and renewables.

(Reporting by Caroline Jacobs; Editing by James Regan and Christian Plumb)