"As summer heat strikes, the US grid increasingly relies on a kind of invisible weapon - the "virtual power plant" - to prevent blackouts. . . . Energy consultancy Wood Mackenzie says the VPPs already deployed or under development in the US will be able to save as much juice as 33 nuclear reactors can produce. . . . The US Energy Department estimates that peak consumption will increase by as much as 200 gigawatts through 2030, and about 80% of that boost could be met through VPPs."