Yes it will! Your gas fireplace, stove or insert generates its own electricity to open and closed the gas valve.
Today’s appliances use one of two types of ignition systems: 1) a standing pilot light, called a “millivolt system” or, 2) an intermittent pilot ignition often referred to as an IPI or electronic ignition system. IPI systems use a battery back-up to open/close the gas valve in the event of a power outage. So, keep fresh batteries on hand! The fan in your appliance is dependent on electricity. It will not operate if power is off to the house. But remember, even if the power is out, you’ll still be able to enjoy the radiant heat from your unit.