London is going to take part in one hour of lights-out across the city on June 21, the summer solstice, from 9pm - 10pm. What a way to celebrate the longest day of the year. Apparently, by not using any electricity for just one hour, the city will save 300 tons of CO2. Amazing. Cities around the world have already held the symbolic, and practical, lights-out events. Hopefully, they will become a normal part of city life rather than just annual statements. +Guardian article on Lights-out London The official site, including a register-your-support page, is at: +Lights Out London Send us your lights-out experiences and please participate!