An hour of electricity

Switch on a classroom light and something starts burning, spinning or shining somewhere else. Following that chain for one hour is a useful exercise, because electricity is the part of daily life whose cost is most completely hidden.

A typical classroom with lights, a fan and a projector uses roughly half a kilowatt-hour in an hour. In a country whose electricity comes mostly from coal and gas, that hour releases a few hundred grams of carbon dioxide. In a country running largely on hydro, wind and solar, the same hour releases almost none. The appliance is identical; the consequence depends entirely on the grid behind the socket.

This explains why two pieces of advice that sound contradictory are both correct. Using less energy always helps, because every unit not used is a unit nobody had to generate. But changing where energy comes from helps far more, because it changes every unit at once, including the ones used by people who are not thinking about it.

Schools sit in a useful position. Their consumption is modest, but they contain the people who will decide these questions in twenty years, and they can make the invisible visible. A meter in the corridor showing the building's current use teaches more in a term than a poster about saving energy, because it responds when somebody acts.

The same principle guided one small design decision in FitForm. The AI runs on the student's own device rather than on a distant server. The energy saved is too small to matter in itself; what matters is that the choice was made deliberately and can be explained.