In addition to the voltage reduction it is possible to reduce overal demand by reducing the frequency.  Frequency reduction has the addition benefit of adding power into the grid.  The energy returned to the grid is related to the mass of the spinning turbines and rotors connected to the grid, which can be quite substantial. Typically a system expresses this term in units of MW per .1 Hz deviation.

One of the worst situations was on the outer islands of the Bahamas, which were run by the Bahamian Electric Company.  Because of development the little network of diesel generators and transformers quickly became overloaded.  Black-outs happened, which is why most residences have their own generators.  But the brown-outs were worse, since they de-rated voltage, frequency, and all kinds of things in an effort to keep electricity flowing.  This proved to be disastrous.

Air conditioners, washing machines, driers, electric ranges, and all sorts of stuff caught fire or simply blew their motors.  Wires melted.  Low voltage conditions can actually be worse than a power surge, it turns out.

Bahamians quickly became excellent little electricians, knowing how to wire a house with surge protectors for lightning strikes and low voltage alarm systems; even the lowliest knew to unplug large electrical appliances or turn off the circuit breakers when away from the house.  They figured out how to integrate small generators so power could be fed to the right stuff at the right kW ratings.  

It's amazing how dumb the average American is about electricity.  Get a windmill or a solar panel and you'll be fascinated by how it all works.  If 10,000 Abaconians in the out islands can do it with no more than a high school education, I'm sure we can manage ...
/sammie

Onward through the fog