During the summer and winter, we tend to overuse electricity because it’s either too hot or too cold.

For instance, during the winter in Boston and other northeastern region, it gets extremely cold. It sometimes reach below zero degrees Celsius.  When you feel very cold, you feel like turning up the heater to be warmer. But at the same time, your next door neighbor will be doing the same thing. At this point, it doesn’t seem like a very big deal, however if you see the pattern, the next door neighbor of your neighbor will be doing the same thing. As you go on with this continuous pattern, the whole state would be having their heater turned up all the way. This means that there will be a lot of electricity being used at the same time. For heaters to be on, electricity must be used to run the machine as well as heat the air that it takes in. As a result, this causes the air to be not warm but rather mild and in some cases, causes the heater to not work for a certain amount of time because the demand is higher than the supply.  To prevent the loss of too much electricity, some companies does a way of preventing over-usage of electricity by responding to the people and companies by demand response.
Demand Response is when a company would limit our electricity usage at specific times of the day during emergencies or  high electricity prices.
But in some cases, the customers/companies can  engage in demand response to receive some payment for helping companies save energies for others.

References:
http://science.howstuffworks.com/environmental/green-science/demand-response.htm

http://www.ecsgrid.com/demand-response-programs/what-is-demand-response-and-how-does-it-work

http://pearcalifornia.com/what-is-demand-response-program