* Total connected to grid now amounts to 3.3 GW
* Push in 2015 due to overhang of missing onshore links
* Next target is 6.5 GW in 2020
FRANKFURT, Jan 18 (Reuters) - Germany connected 2.3 gigawatts (GW) of newly built offshore wind capacity to electricity networks, engineering association VDMA said on Monday, adding that this was a one-off that would not be repeated.
Europe's largest economy in 2015 added the 2.3 GW of actively producing turbine power to the existing 1 GW, bringing total capacity by the end of 2015 to 3.3 GW derived from 792 production units.
"It is a one-off record because it results from delayed effects through the necessary connection to onshore grids," VDMA said of progress in 2015.
Some 41 units, with a combined capacity of 246 megawatts (MW), were constructed last year but still need to be hooked up this year, while another 122 foundations were laid for the future construction of turbines, VDMA said.
Citing a report gathered by researchers Deutsche WindGuard that was commissioned by industry groups, it forecast 700 MW of total capacity additions this year.
Offshore wind, which is part of the country's push into renewable power, has faced hurdles in getting off the ground.
The long distance between the turbines and the mainland, due to environmental factors, raised costs and caused delays due to technical challenges.
Industry statistics group AGEB said the industry produced 8 terawatt hours (TWh) of power last year, enough to supply 2 million households, but accounting for just 1.4 percent of total German production, offshore is still a niche technology.
The government, which will enact a renewable law overhaul this year, envisages a total 6.5 GW of offshore wind capacity by 2020 and 11 GW by 2025.
The law reform will change fixed-price schemes of the past to auction-based models, bringing green energy gradually into the wholesale power market and away from a costly era of subsidies.
Companies such as Siemens, ABB and Alstom are vying to provide transmission technology for onshore grid companies TenneT IPO-TTH.AS and 50Hertz that receive and distribute the electricity. (Reporting by Vera Eckert, editing by Louise Heavens)