It might be useful to point out that many gas appliances, furnaces stoves and heaters, use electrical power to run blowers and controls and many of these won't work at all without line power. Check your manual, ask your regular service tech or, a useful way to double check and avoid misconceptions, turn off the power at the mains and see what is still kicking.

Some of those that use line power use such minuscule amounts of power to run timers and controls that some of them can be inexpensively set up with a small battery backup. Others can be bypassed even if it requires that you operate the unit manually. All of which is a lot easier to figure out and adapt before any emergency.

How you adapt any system is going to vary with your system and installation. A sympathetic and highly knowledgeable service technician is your best guide. It has to be noted that such modifications require an exceptional amount of engineering skill, inventiveness and knowledge to operate outside the margins. Your average technician that has to operate out of a standard flow chart won't be much help.