Follow The Money: Demand Charges

WHAT IS A DEMAND CHARGE?
Think of it as the “size of the pipe” that delivers electricity to customers,
. . . a bigger pipe costs more, but can deliver more juice at any instant.

Now consider 2 hypothetical residential customers,
. . . both with the same monthly kWh usage:

Customer A: Uses approximately the same number of kWhs each day.
. . . The customer works at home, and has a consistent demand throughout the day.

Customer B: has rooftop solar, and an electric vehicle.
The rooftop solar ramps up production, just as they shut off all electric usage,
. . . leaves for work, and exporting surplus solar PV.
Solar production decreases in the afternoon, when they get home,
. . . turn on all electric usage, and plug in an electric vehicle.

05-27-2015 Source:  Follow the Money: Demand Charges