Yes. That is one of the better arguments for essential-circuit backup instead of a whole-house standby system. Honda’s Home Applications table lists gas or oil furnace fans from 1/8 hp (300 W running, 500 W starting) through 1/3 hp (700 W running, 1,400 W starting) and 1/2 hp (875 W running, 2,350 W starting). Combined with a refrigerator and a few lights, the 1/3 hp case is the about 1,292 running watts and 2,300 starting watts already walked through on the essentials page. You still need a lawful way to feed that furnace circuit: a listed interlock or a small transfer switch and an inlet, not a cord into a basement window.
A furnace that is already on a dedicated breaker is easier to include in an essential-circuit transfer switch. An interlock lets you choose that breaker by hand and leave the dryer and the range off. A small UPS may keep the control board alive through brief blinks, but it is not a substitute for a generator during a long outage and should be discussed with the HVAC technician, not improvised from a website.
This does not apply to an electric furnace or to a heat pump with resistance strips — those are whole-house or large-standby problems. Use the calculator, place the generator outdoors at least 20 feet from the house, and pull a permit for the inlet and transfer equipment.
This is not a permit calculation, a utility approval, or a substitute for a licensed electrician, HVAC contractor, or the authority having jurisdiction. Panel Headroom is an independent educational site. It is not a utility, a certification body, or a contractor. Electrical and generator work that is done incorrectly can cause fire, shock, or carbon monoxide poisoning. Use the adopted electrical code and manufacturer instructions; pull permits where required.