According to the BBC, reports abound on social media that the UK's energy grid is to see a fall then a surge during the eclipse on the 20th March as people stop what they're doing and go outside to watch the event.
The National Grid, however, says that it is an entirely manageable event from their end, as the UK only generates 1GW of power from solar at this time of day. Amazingly, the fall is expected to exceed the dropoff from loss of solar capacity (1100MW vs. 850MW), post eclipse to surge by just 950MW which is still less than the total solar capacity (5GW). The math bears out NG's statement, as does practically the entire history of power distribution in the UK, which has seen large swings in power demand on an hourly basis and the Grid managing to cope just fine.
Previous Major Event Surges:
It should be noted that these power surges did not generate any significant problems worthy of reporting anywhere. The last actual power crisis in England occurred during the 1984 coal strike, when baseline generators actually ran out of fuel.
(Score: 1) by Megahard on Saturday March 21 2015, @04:12PM
That's a popular Internet legend, generally taken not to be true, at least to the point where sewers and treatment plants overflow.
http://www.snopes.com/sports/football/flush.asp [snopes.com]