At 8:30 pm tonight (in your local time zone), 27 March, millions of believers in Anthropogenic Global Warming (AGW) will switch off their lights. This will cause disruption at the supply end. See:
In order to counteract this disruption to the power supply it is up to non-believers of AGW to switch on their appliances. Power stations that use boilers won't even save that much power during Earth Hour -- it will be wasted.