Underlying operating profit rose to 13.5 billion Swedish crowns ($1.28 billion) from 9.1 billion a year earlier, the state-owned company said.
"Wind power doubled its contribution. We are also seeing more customers choosing Vattenfall in uncertain times," Chief Executive Anna Borg told Reuters.
Vattenfall had last month said it was investigating the possibility of building 2.8 gigawatts of new nuclear capacity at its existing Ringhals site on the western Swedish coast and connecting it to the grid from 2032.
Borg said the result of the feasibility study, exploring building at least two small modular reactors, would come later this year and that it was too early to say if Vattenfall would go ahead with the investments.
"But we are particularly pleased that nuclear power is now seen as a natural part of the Swedish energy mix, we need all fossil-free energy sources," Borg said.
Sweden's centre-right government is preparing legislation to allow the construction of more nuclear power stations to boost electricity production in the Nordic country and bolster energy security.
Vattenfall made an operating loss of 24.1 billion Swedish crowns in the fourth quarter, mostly because of changes in market value for energy derivatives, which Borg said were temporary and would even out over time.
It achieved a price of 135.61 euros per megawatt hour (MWh) for its Nordic power production in the quarter, up 41% from a year-earlier 96.24 euros/MWh.
($1 = 10.5310 Swedish crowns)
(Reporting by Johan Ahlander; editing by Niklas Pollard and Arun Koyyur)
