The extreme cold is churning up demand for electricity that is normally only seen during the extreme heat of summer.
The company that runs ComEd's power grid is asking customers to conserve power.
The system's being strained by furnaces that are pretty much running around the clock.
The grid company is asking customers to put off running appliances like dish washers, and to turn off lights that aren't being used.
Additionally, officials warn that customers will see higher utility bills because of the heavy furnace work.