* 30 GW of wind, 5 GW of biomass capacity by 2020
* Around 6 GW of interconnectors by 2020, 8.6 GW by 2030
LONDON, Sept 27 (Reuters) - Britain could be exporting more electricity than it imports by the early 2020s as growing renewable energy output and construction of new interconnectors will help it ship more power to its neighbours, the grid operator said in a report on Thursday.
While Britain's domestic gas production continues to decline, increasing dependence on pipeline and liquefied natural gas (LNG) imports, its power market could turn from a net importer to exporter within 8 years.
"We expect both annual imports and exports to rise from current levels in line with the increase in interconnection capacity, with exports increasing markedly from the latter part of this decade onwards as renewable generation increases so that GB becomes a net exporter to the continent by the early 2020s," National Grid, said in a report analysing the long-term future of the country's energy networks.
In a scenario where Britain will meet its 2020 target of generating 15 percent of its energy demand from renewable sources, but does not exceed it, the country could have the help of 30 gigawatts (GW) of wind and 5 GW of biomass capacity to keep the lights on by 2020, National Grid predicted.
The British government has created an attracive renewable energy subsidy scheme, through which is expects 31 GW of wind capacity and 6 GW of biomass in Britain by 2020, roughly in line with National Grid's estimate.
On top of high amounts of renewable energy capacity, Britain will be connected to other markets through cables of around 6 GW in size, rising to 8.6 GW by 2030, allowing it to send excess power production to markets in France, the Netherlands, Norway and Belgium.
Last year, Britain imported 8.7 gigawatt-hours (GWh) of electricity and exported 2.5 GWh, making it a net importer of power, but National Grid said the trend could reverse if Britain's renewable energy expansion continues as planned.
The government is also banking on a series of new nuclear power reactors to start operating by 2025 to help meet its climate targets.
In the same scenario described above, National Grid predicts only one nuclear power plant can connect to the network in the early 2020s, but capacity can reach just over 10 GW by 2030.
Nuclear power plant developers said they could build 16 GW in new capacity by 2025, but Japan's Fukushima accident and difficulties to secure funding have delayed plans.