Germany will need to spend $25 billion over 10 years to upgrade its transmission network to accommodate a switch to renewable power, grid operators say.

The country's four main grid operators -- 50Hertz, Amprion, TenneT and TransnetBW -- laid out the estimate this week in Bonn at the request of German Chancellor Angela Merkel, who vowed to make the grid changes necessary to complete the phase-out of the country's nuclear power plants.

She said the proposed upgrades, dubbed the National Grid Development Plan, are feasible and would help the country succeed in a "demanding and exciting" effort to reorient its electric grid to tap new supplies of wind energy generated in northern Germany, Deutsche Welle reported.

"The transition is feasible in the way we decided it a year ago. And of course we will stick to our pledge to phase out nuclear energy by 2022," Merkel said at the Federal Network Agency in Bonn.

"The better the network and the technology, the more likely it is that we will be able to use the full potential of renewables, guarantee a power supply and keep the costs at an acceptable level," added Environment Minister Peter Altmaier.

The draft plan laid out by the grid operators calls for 2,400 miles of new power lines, including 1,300 miles of long-distance direct current lines similar to those used for undersea connections between Britain and continental Europe, and well as 1,100 miles of standard alternating current lines.

That would be in addition to a current round of 870 miles of alternating current lines already either under construction or planned under a existing 10-year-old, $8.6 billion grid upgrade scheme, the Financial Times reported.

"The expansion of the transmission network accounts for only a fraction of the cost of the energy transition (to renewables) but will account for much of the success of its implementation," grid operators said in the plan.

"These are long-term investments in lines that are available for several decades and will contribute to the security of supply from renewable sources and the development of the electricity market," they declared, urging a "quick approval process" to meet Merkel's goal of a 2022 nuclear phase-out.

That could be a problem judging from the slow progress of efforts to build new north-to-south power lines from Germany's burgeoning offshore and onshore wind power developments in its northern provinces. Building such lines is a long process, taking 10 years in many cases, and they lines are often bitterly opposed by local residents and environmentalists.

But Merkel said the process must be speeded up accommodate the smaller, local nature of renewable power generation.

German Association for Renewable Energy President Dietmar Schutz hailed the plan as evidence of the feasibility of adapting the country's power grid and said it can be accomplished "if everyone pulls together."

The $25 billion cost is acceptable if viewed as the long-term infrastructure investment it is, he said, asserting the costs would work out to no more than 0.5 cents per kilowatt hour.

"We now have a common basis for a broad discussion," he said. "The priority projects for network expansion can now be identified and then be quickly brought to the widest possible consensus on their routes."