Phoenix and the East Valley see plenty of nights in the 40s and 50s, with occasional dips below freezing in outlying areas. Most homes run either a gas furnace, a heat pump, or a dual-fuel setup. Each needs a different pre-season checklist, and confusing the two is a common reason for “no heat” calls on the first cold morning.
Gas furnace checklist
- Replace the filter — a clogged filter is the number-one cause of limit switch trips.
- Test the thermostat in heat mode before you need it; switch batteries if it is wireless.
- Listen for delayed ignition or booming at startup — that can indicate burner or ignition issues.
- Check that vents and returns are open and unblocked by furniture or stored items.
- Confirm carbon monoxide detectors are working and less than ten years old.
Heat pump checklist
Heat pumps heat efficiently in mild Arizona winters but switch to auxiliary heat strips during hard cold. If your bill spikes overnight during a freeze, aux heat may be running more than it should — often due to a stuck reversing valve, low refrigerant, or a thermostat setting that forces emergency heat.
- Clear leaves and debris from the outdoor unit so defrost cycles work properly.
- Avoid cranking the thermostat more than 2° at a time — that reduces strip heat use.
- Schedule service if the outdoor unit never seems to defrost (heavy ice for hours).
When repair beats replacement
If your furnace is over 15 years old and needs a heat exchanger or major gas valve work, compare repair cost to a new high-efficiency unit. For heat pumps past 12–14 years with repeated refrigerant leaks, replacement often pencils out over five years of electric bills in Gilbert and Queen Creek–style new builds with tight envelopes.
