* Germany shuts nuclear units, buys power from abroad
* Domestic coal, gas capacity may be driven harder instead
(Adds grid operator comment in paras 10, 11)
By Vera Eckert
FRANKFURT, April 4 (Reuters) - Germany has become a net power importer from France and the Czech Republic since shutting its oldest nuclear plants last month, utility group BDEW said on Monday, sourcing much of it from reactors abroad.
German wholesale power prices have surged since the government ordered seven of the country's oldest nuclear plants to shut after a tsunami crippled a Japanese plant on March 11.
Berlin's reaction has made Europe's biggest economy a more attractive market for nuclear power producers such as EDF and CEZ.
Since the March 17 order to close around 7,000 megawatts (MW) of nuclear capacity, Germany gas gone from being a net exporter of 70-150 gigawatt hours (GWh) a day to a net importer of 50 GWh of electricity a day, BDEW said on Monday.
"Power imports from France and the Czech Republic have doubled," BDEW said. "German power exports to the Netherlands and Switzerland have halved."
France gets more than 80 percent of its electricity from nuclear plants, and the Czech Republic generates around a quarter of its electricity from reactors and most of the rest by burning coal.
Some of Germany's lost nuclear capacity has been made up for by burning more coal, which has driven up coal prices, increased Germany's climate-warming gas emissions and driven up the price of EU permits to pollute..
Wholesale prices of German quarterly power in 2011 and the benchmark contract for round-the-clock power supply in 2012 have both risen by 12 percent, BDEW said.
Germany has some cleaner burning gas plants, which could run for longer, but it currently makes more economic sense to import power from French nuclear reactors or Czech coal and nuclear plants than running Germany's gas plants around the clock.
For the short term, Germany's neighbours have enough spare plant capacity to keep systems supplied and in balance, European grid operators' group Entso-E said.
But if summer peakload demand, driven by heightened air conditioning needs, coincides with the nuclear shutdowns in Germany, reserve power supply margins may shrink, Entso-E Secretary General Konstantin Staschus told Reuters.
In the longer term, German utilities plan big capacity increases to make up for the loss of nuclear energy, BDEW said, hours before Germany's deputy environment minister said all nuclear plants should be shut down before 2020.
"In the medium term, other strategies may be used, for example greater exploitation of existing, conventional domestic capacity (coal and gas-based)," it said.
"This will depend among other things on the central European merit order," it added, referring to a market mechanism whereby the first plants to be used are those with the lowest marginal costs.
For a table issued by BDEW on German power station investment plans please click on
(Additional reporting by Tom Kaeckenhoff in Hanover, writing by Daniel Fineren; editing by Jane Baird)