Smart grid

A smart grid is an ordinary electricity network with a nervous system bolted on: sensors, smart meters and software that let operators see and steer the flow of power almost in real time, rather than running the wires half-blind and reacting after the fact.

Cities want this because clean power is unpredictable. Solar and wind rise and fall with the weather, and buildings increasingly generate their own electricity, so the grid has to balance thousands of small, shifting sources against demand second by second. In Honolulu, where nearly half of single-family homes carry rooftop solar, Hawaiian Electric's smart meters and telemetry help balance that flood of variable generation; Tokyo's Harumi Flag district runs an energy-management system that predicts each block's peak demand; and Dresden's Kaditz wastewater plant generates about 85% of its own electricity, acting as a producer as well as a consumer.

The trade-offs are real. Rebuilding a grid to be "smart" is expensive and slow, the added connectivity widens the target for cyber-attacks, and smart meters raise privacy questions because detailed consumption data reveals when a home is occupied. A microgrid applies the same intelligence to a small, self-contained patch of network. The intelligence is only as good as the data and controls behind it.