KOLKATA: Almost 26 GW of demand dropped between 9 PM and 9.15 PM on Sunday. Around 16.6 GW of power demand dropped between 9 PM and 9.05 PM when citizens started observing Prime Minister, Narendra Modi ’s call to switch off lights and light candles. In the next ten minutes another 9 GW power demand dropped, taking the total fall between 9 PM and 9.15 PM to almost 26 GW. Demand started to rise shortly after 9.15 PM.The national power grid was prepared for the fall in demand and has been gradually scaling down thermal power generation in steps since 7.30 PM. In tandem power generation from gas-based and hydel generation units were being scaled up to maintain the balance.At 9 PM hydel was generating around 23.9 GW which was scaled down to half within three minutes to 12.22 GW when overall demand dipped as lights were switched off. Hydel power generation has one of the highest flexibilities of scaling down and increasing generation within a short time and the grid management authorities took advantage of flexibility. Renewable power generation were also scaled down by half around 9.15 PM.As demand started to rise, thermal, hydel and gas-based generation was gradually scaled up for meeting the rise in demand. While thermal was being scaled up at a slow pace, hydel and gas based power generation was rapidly increased to maintain grid balance.At 9 PM demand was 114,456 MW which declined to 97,798 MW in about five mines. In the next ten minutes it touched 88,759 MW after which it started to rise and was 111,040 MW at around 9.40.