What actually keeps heating when power drops?
During an outage, fuel availability and electrical dependency decide whether heat continues. Systems with standing pilots and no electric fans (e.g., some gas fireplaces, propane stoves, gravity wall heaters) can still produce heat. Most modern forced-air gas furnaces use an electronic ignition and an electrically driven blower, so the burner and safety controls may be gas-ready, but no airflow = no heat without generator power. Electric heat strips are 100% dependent on electricity, no power, no heat unless you have a suitably sized generator or battery.
In older millivolt systems, the pilot’s thermopile powered the gas valve without utility power. That’s rare in new equipment. If you rely on forced air, plan to power the blower, ignition, and control board.
Pair outage-capable room heat (gas fireplace/propane stove or unit heater) with your central system to keep at least one living zone above freezing.
Gas & Propane Backup: Fast heat and better comfort in deep cold
Gas and propane deliver high-temperature supply air (≈120–140°F) that feels warm even in sub-freezing weather. That higher delta-T drives quicker room recovery and more reliable freeze protection. If your backup is a vented gas fireplace or propane heater with a standing pilot, you can maintain habitable temps during an outage without running a large generator. For forced-air gas furnaces, count on powering the blower motor (ECM/PSC) and controls with a small to mid-size generator.
Safety & service: Maintain venting, test CO alarms, and schedule annual burner inspections. Propane systems need tank monitoring and regulator checks.
Where it fits: Cold climates, frequent outages, and homes that need whole-house recovery post-outage.
Electric Heat Strips: Simple, common and heavy on amperage
Electric strip heat is straightforward: resistive elements heat air like a giant toaster. Expect 85–95°F supply air—adequate for mild climates but less satisfying in deep cold. The trade-off is amp draw. A 10 kW strip at 240 V draws ~42 A (plus blower), and larger air handlers may stage 15–20 kW or more. That has two implications: higher utility bills in the heating season and larger generators for outage operation.
Design tips: Use staged or sequenced strips and verify breaker sizing, wiring, and airflow to keep elements from cycling on limit. Inverted-time delays prevent lights-dimming starts on generator power.
Best uses: As backup to a heat pump in milder regions or where utility power is reliable.
Heat Pumps with Backup: Dual-fuel vs. all-electric strategies
Pairing a heat pump with backup heat is standard practice. In all-electric setups, strips engage below a balance point or during defrost. In dual-fuel, a gas furnace takes over in colder temps, delivering higher supply temperatures with better efficiency at deep-cold conditions. Dual-fuel systems shine in regions with swing climates—using the heat pump for shoulder seasons and gas for hard winter.
Controls matter: Set intelligent switchover (outdoor temperature, utility rates, or demand response). Verify airflow and coil sizing so defrost and changeover are smooth.
Where it fits: Mixed climates, homes wanting comfort + redundancy without oversizing strips.
Generator Sizing: Blowers vs. strips (avoid the “too small to help” mistake)
Rule of thumb: Gas backup usually needs power for blower + controls (≈0.3–1.0 kW continuous; higher on startup). Electric strips require the full kW rating of the elements plus blower and some headroom.
Quick math:
-
10 kW strip ≈ 10 kW load (resistive) + blower (≈0.3–0.8 kW) → recommend ~12–14 kW generator minimum.
-
Gas furnace blower/controls ≈ 0.5–1.5 kW → many homes get by with 2–5 kW if loads are managed.
Use lockout relays to disable strips while on generator, and soft-start/VFD solutions to tame inrush where applicable. Label the panel for outage mode.
Accessories: Transfer switches, surge protection, and thermostat programming tools live here: Accessories.
flowchart LR
A[Outage] --> B{Fuel available?}
B -- Gas/Propane --> C{Needs blower?}
C -- No --> D[Use standing-pilot heater]
C -- Yes --> E[Power blower with 2–5 kW gen]
B -- Electric Only --> F{Strips?}
F -- Yes --> G[Gen ≥ strip kW + blower]
F -- No --> H[Consider wood/propane room heat]
Wood Stoves & Fireplaces: Off-grid heat that just works
When the grid goes down, wood stoves and vented gas/propane fireplaces continue to heat without utility power. They’re ideal for freeze protection and zone heating. Look for models with gravity airflow or standing pilots to avoid reliance on electric blowers. Keep clearances, hearth protection, and venting per code.
Air quality & safety: Wood combustion produces particulates—use seasoned wood, keep the flue clean, and consider a HEPA-capable purifier in tight envelopes. Maintain CO/smoke alarms and proper outside air provision where required.
Where it fits: Rural areas, frequent multi-hour outages, cabins, or homes wanting a resilient “warm zone.”
Add-ons: If you heat a garage/shop during outages, look at unit heaters; for rooms without ducts, consider mini-split consoles.
Climate Playbook: Cold, mixed, and mild regions
Cold climates: Prioritize gas/propane or dual-fuel for higher supply temps and faster recovery. Keep a small generator for the blower/control board and a pilot-equipped room heater as a fallback.
Mixed climates: Heat pumps excel most days; use dual-fuel or modest strips for cold snaps. Add a gas fireplace to create a resilient heat island during extended outages.
Mild climates: All-electric is practical; just remember that strips need large generators to operate in outages. For resilience, add ductless heat pumps in key rooms.
Right-size everything: Use the Sizing Guide and, if you need design help, our Design Center.
Ignition, Controls & Pilot Reliability: What the labels don’t say
Standing pilot systems with no electric fans can heat without grid power. Electronic ignition (hot surface or spark) needs electricity even if fuel is available. Most modern furnaces pair electronic ignition with an ECM blower, improving efficiency but requiring generator/battery during outages.
Controls checklist: Does your thermostat/air handler lock out strips on generator? Are defrost and outdoor fan on the outage plan for heat pumps? Do you have low-temp cut-in set correctly for dual-fuel switchover?
Service tip: Keep a spare flame sensor and ignitor, verify grounding, and test condensate safeties (condensing furnaces) before winter.
Learn more or troubleshoot: Visit the Help Center and HVAC Tips blog.
Cost & Efficiency: Installation vs. bills (and where the money goes)
Upfront, gas systems cost more due to fuel piping, venting, and safeties. Operating costs, however, are typically lower per BTU than electric resistance, especially in cold climates. Heat pumps offer excellent efficiency in mild to mixed weather, but when strips carry the load, bills climb quickly.
Budgeting cues:
-
If outages are frequent, the generator you’d need for strips often costs more than powering a gas blower, tipping the lifecycle math toward gas/dual-fuel.
-
If outages are rare and winters are mild, all-electric may still be the best total-cost choice.
Questions on shipping, returns, or policies? See Help Center. Prefer to talk it through? Contact Us we’ll spec the right backup heat and generator pairing for your home.
