How many protesters were there, really? 12 million, according to National Grid

Lots of numbers have been flying around over the past few days

with many claiming it was the largest protest in history, but stopping short of presenting facts & figures to back this up.

National grid reported that it saved 2000 Gigawatt last week due to people protesting in the street and thus reducing their electricity consumption. 

By doing the math, 2000 Gigawatts means 2 billion Kilowatt.hour were saved last week, by dividing this number by the average consumption per capita (1.5 Mwatt.hour) at least 1.3 million were in the streets at any given time, that means 12 Million were in the streets during the peak time of the protests.