Keeping the Heat On in an Outage - A Plain-English Furnace Backup Guide
Last verified: September 2026
Everything you need to know to keep your furnace or boiler running on a generator — what it actually needs, why it calls for a proper hookup, and the honest truth about electric heat. Rather have a hand deciding? My number is (330) 200-8042.
Keeping the Heat On, at a Glance
A gas or oil furnace doesn't make its heat from electricity — it needs power mostly for its blower fan and controls, which is a modest, manageable job for a generator. This guide covers that starting surge, why the furnace needs a proper transfer switch or interlock rather than a cord, and the honest truth about electric heat, which is a very different story. There's a printable page-by-page version up top.
Common Questions
1 Does my furnace need a huge generator?
Usually not, if it's gas or oil — the furnace mostly needs power for its blower fan and controls, a modest load with one starting surge to plan for. Electric heat is the exception; see below.
2 Can I run a cord to my furnace instead of a transfer switch?
No. A furnace or boiler is hardwired into your panel, with no plug to reach. It needs a transfer switch or interlock, installed by a licensed electrician.
3 Will a generator run my electric furnace or heat pump?
Be careful here — electric heat makes the warmth itself with electricity, and often draws far more than a typical portable generator can comfortably supply. Treat this as its own honest conversation before you buy.
4 Is it safe to run the generator in the garage to keep it out of the cold?
No. Even with the door open, a garage can trap dangerous carbon monoxide. The generator stays outside, well away from the house, in every season — see our carbon monoxide guide.
5 Can I use a space heater while I sort out the furnace hookup?
An electric space heater, used with care and never left unattended, can help in one room. Never use a fuel-burning or unvented heater indoors — it carries the same carbon-monoxide risk as an indoor generator.
6 What if my home has a boiler instead of a furnace?
Similar picture — a boiler's circulator pump (or pumps, for multi-zone systems) is a motor with its own starting surge, alongside a small, steady draw for controls and ignition.
Would You Rather I Just Help?
Keeping the heat on is one of the most common reasons folks call me about a generator. I'll help you figure out what your furnace or boiler actually needs, size it honestly, and line up a licensed electrician for the hookup. $99 flat for a visit, 30-day come-back-free.
Would you rather I just do this for you?
No shame in it — plenty of folks would rather hand it off, and that's what I'm here for. I'll come to your home, set it up right, and make sure it's working before I leave. Flat $99 per visit — no jargon, no upsell, and every visit is 30-day come-back-free.
Not a hardware job? I can often fix it remotely for $49 — a secure screen-share, up to 2 hours, that you watch the whole time and can end whenever (included free for $39/mo Support Plan members, and it counts toward the $99 if it turns out I need to come out).