The last solar eclipse took place in 1999, when a tiny percentage of electricity supplies relied on solar energy. Now, nearly 3 percent of Europe's total electricity supplies are dependent on the sun, according to Eurostat.
Transmission system operators have been preparing for the eclipse for months, ENTSOE said, but warned it still posed a threat to Europe's electricity system.
"Despite …preparations and coordination, the risk of incident cannot be completely ruled out," the group said in a press release.
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The eclipse is expected to cast a shadow across Europe for a few hours, and will affect countries stretching from Turkey to Greenland and Spain to Norway.
But John Meyer, analyst at mining and energy broker SP Angel, said he did not expect the eclipse to be a huge issue. Grid operators would have planned to compensate for any drop in power with gas-fired generation, he told CNBC, "as they would use to cover any normal power shortfall."
"You could equally worry about volcanic ash clouds and dust storms," he said via email. "Solar farms are almost always combined with power from other sources to improve reliability. As a result, we don't see the event of an eclipse lasting long enough or make much of a difference."