* Rapid expansion of wind, solar on the cards
* Energy regulator, grid operators must provide infrastructure
* Power usage, maximum load on networks seen stable to 2022 (Adds details from press conference)
By Vera Eckert
BONN, Dec 7 (Reuters) - Germany is set to expand its onshore wind power capacity by 1.7 gigawatts (GW) a year up to 2032, its Federal Network Agency said on Wednesday after studying the impact of a planned rapid expansion of green power in Europe's biggest economy.
It would arrive at 47.5 GW in 2022 and 64.5 GW in 2032, compared with 27.1 GW of capacity installed in 2010, the agency's president Matthias Kurth said at a news briefing.
The authority, which supervises grids, said it looked realistic that fledgling offshore wind capacity could reach 13 GW in 2022 and 28 GW in 2032.
Solar power may reach 54 GW in 2022 and 65 GW in 2032, it said.
The figures are important to gauge subsidy levels for renewable power, which under German law must be shared by all consumers, the requirements for transmission grid expansion, and for future network stability, given that renewables are volatile as a power source.
"We are describing what we would need so that we can say that in 10 years' time, we will have secure supply and networks," Kurth said.
"We will need a realistic grid expansion plan based on our data, otherwise the ambitious energy strategy change cannot materialise," he added.
Germany has embarked on a strategy shift away from fossil-fuels based production towards green power, and Kurth has a brief to commit transmission firms and generators to ensure the right infrastructure is installed in a coordinated fashion.
Wednesday's data will serve as the basis for plans the transmission firms must present next June, in order for the government to finalise grid expansion laws from 2013.
The maximum load on the high-voltage grids - reflecting top demand - was assumed to remain steady at 84 GW in a scenario up to 2022 and German power demand was assumed to be steady at 535.4 terawatt hours (TWh), the agency said.
These are sensitive figures as Germany's hasty decision this year to abandon nuclear energy earlier than planned was feared to be causing stress on networks at high demand times and when renewable supply is not available due to weather patterns.
Despite zero fuel input and no carbon emissions, the problem with renewablespower is that without the right weather, there may not be enough production when needed.
Power cannot yet be stored in great amounts and Kurth said that prospects for effective solutions were 20 to 30 years away.
The stable demand figure up to 2022 was based on the assumption that energy efficiency gains would offset consumption increases arising from economic growth, he said.
The stable load figure hinged on assumptions that better grid usage and management, and new cables, will help rein in potential overloads or disruptive load swings on the grids.
More short term, Kurth reiterated that this and next winter looked supplied enough to cope with the loss of a huge slice of nuclear energy earlier this year, when Germany shut its oldest reactors in the wake of the Fukushima disaster.
The Bundesnetzagentur in August made provisions for coal-fired plants to rev up capacity at times of undersupply after off 41 percent of Germany's former nuclear capacity was switched off permanently.
"We have said we should keep a handle on the situation and there are no renewed doubts," Kurth said. (Editing by William Hardy)