Nothing runs
The thermostat looks blank or normal, but neither the indoor unit nor the outdoor unit starts heating.
Start here: Check thermostat power and settings first, then the HVAC breakers and any outdoor disconnect.
Heat pump heating problem
Heat Pump No Heat After Outage
Direct answer: When a heat pump quits heating right after an outage, the most common causes are a tripped breaker, a thermostat that lost settings, an outdoor disconnect left off, or the system sitting in a delay before restart.
Most likely: Start by confirming the thermostat is calling for heat, the air filter is not packed, and both the indoor and outdoor units actually have power.
Power outages leave a lot of heat pumps looking dead when the real problem is simpler: one side of the system lost power, the thermostat reset, or the unit is locked in a short protection delay. Reality check: many systems need several minutes before they will restart normally. Common wrong move: flipping breakers on and off repeatedly and calling that a reset.
Don’t start with: Do not start by replacing capacitors, boards, or the thermostat just because the outage happened first.
If the indoor blower runs but the air never gets warm,separate a power problem from an airflow or outdoor-unit problem first.
If nothing runs at all,treat it like a power or thermostat issue until proven otherwise.
Last reviewed: 2026-04-05
What this usually looks like after an outage
Indoor blower runs, but air feels cool
You get airflow at the vents, but it never turns warm enough to heat the house.
Start here: Check whether the outdoor unit is running and whether the filter or return airflow is badly restricted.
Outdoor unit is silent
The indoor unit may run, but the outdoor section is dead after the outage.
Start here: Look for a tripped breaker, pulled disconnect, or a system delay before restart.
System starts, then stops or never catches up
The heat pump runs oddly after power returns, may click, hum, or rely only on backup heat.
Start here: Check for a dirty filter, iced outdoor unit, or a fault condition that needs service rather than more resets.
Most likely causes
1. Breaker tripped or only one side of the system has power
After an outage, it is common for either the air handler breaker or the outdoor unit breaker to trip. A heat pump can act half-alive when only one section has power.
Quick check: At the main panel, look for an HVAC breaker that is centered or not fully ON. Also check the outdoor disconnect if your system has one.
2. Thermostat settings reset or the thermostat is not actually calling for heat
Some thermostats lose schedule, mode, or temperature settings after a power interruption. The screen may be on, but the system is not being told to heat.
Quick check: Set mode to HEAT, fan to AUTO, and raise the set temperature at least 3 to 5 degrees above room temperature.
3. Restart delay or lockout after the outage
Many heat pumps wait several minutes before restarting to protect the compressor. Some will also lock out after unstable power until power is fully reset once.
Quick check: After confirming settings and power, wait 5 to 10 minutes without touching anything and listen for the outdoor unit to start.
4. Airflow restriction or an outdoor unit fault that showed up when power returned
A packed filter, blocked coil, or failed outdoor component can leave you with blower airflow but little or no heat. The outage may have exposed the problem rather than caused it.
Quick check: Check the filter, open supply and return vents, and see whether the outdoor fan or compressor tries to start, hums, or stays completely still.
Step-by-step fix
Step 1: Set the thermostat up for a real heat call
A lot of outage calls end here. The thermostat may be on, but in the wrong mode, on a schedule, or not asking for enough heat to start the system.
- Set the thermostat to HEAT.
- Set the fan to AUTO, not ON.
- Raise the set temperature 3 to 5 degrees above the current room temperature.
- If the thermostat has batteries and the screen is weak, replace them.
- If the thermostat recently rebooted, cancel any hold, vacation, or schedule override that keeps it from calling for heat.
- Wait a full 5 minutes after changing settings before judging the result.
Next move: If the system starts and begins heating normally, the outage likely reset the thermostat or the system was in a restart delay. If nothing changes, move on to power checks before assuming a failed part.
What to conclude: You want to prove the system is actually being asked to heat before chasing deeper faults.
Stop if:
- The thermostat is blank and does not come back after basic battery replacement.
- You smell burning, hear arcing, or see sparks at the thermostat or equipment.
- The thermostat wiring is exposed or damaged.
Step 2: Check both power points: breaker panel and outdoor disconnect
Heat pumps usually need power at the indoor unit and the outdoor unit. After an outage, one breaker can trip while the other stays on, which creates confusing symptoms.
- At the main electrical panel, find the HVAC breakers for the indoor air handler or furnace section and the outdoor heat pump section.
- If a breaker is tripped, turn it fully OFF once, then fully back ON once.
- Do not keep resetting a breaker that trips again.
- If there is an outdoor disconnect near the unit, make sure it is inserted correctly and switched on if applicable.
- Go back to the thermostat and call for heat again, then wait several minutes.
Next move: If the outdoor unit and indoor unit both come back and heat returns, the outage likely left one side without power. If a breaker trips again or the outdoor unit still stays dead, stop resetting and treat that as a service issue.
What to conclude: A repeat trip points to an electrical fault, seized motor, compressor problem, or short that is not a safe DIY repair.
Stop if:
- Any breaker trips more than once.
- The disconnect looks burned, loose, wet inside, or damaged.
- You are not comfortable working around the electrical panel.
Step 3: Separate a no-power problem from an airflow problem
If the blower runs, homeowners often assume the whole heat pump has power. That is not always true. This step tells you whether the outdoor side is participating.
- Stand near the outdoor unit after the thermostat has been calling for heat for at least 5 minutes.
- Listen for the outdoor fan and compressor. A normal unit will usually hum and move air.
- If the outdoor unit is silent, note that the problem is likely power, control, or an outdoor component fault.
- If the outdoor unit runs but the air indoors is still weak or barely warm, check the air filter.
- Replace a heavily loaded heat pump air filter with the correct size and airflow direction.
- Make sure return grilles and supply registers are open and not blocked by furniture or rugs.
Next move: If airflow improves and the house starts warming again, the filter or blocked airflow was holding the system back. If the outdoor unit is still not running, or it runs but heat output stays poor, the problem is beyond a simple reset or filter issue.
Stop if:
- The outdoor unit only hums, buzzes, or clicks without starting.
- You see ice buildup, oil residue, or damaged wiring at the outdoor unit.
- You would need to remove electrical covers or access sealed refrigerant components.
Step 4: Give the system one clean reset, then watch what comes back
After unstable power, one clean reset can clear a temporary lockout. Repeated resets usually waste time and can make the situation less clear.
- Turn the thermostat OFF.
- Shut off the HVAC breakers for both the indoor and outdoor sections once.
- Wait 5 minutes.
- Turn the breakers back ON.
- Set the thermostat back to HEAT and raise the setpoint.
- Wait 10 minutes and watch for this order: indoor blower, outdoor unit start, then warmer air at the vents.
Next move: If normal operation returns after one clean reset, the outage likely left the controls in a temporary delay or lockout state. If the sequence does not return, or only the blower comes on, stop resetting and move to the final decision step.
Step 5: Decide between a supported homeowner fix and a service call
By now you should know whether this was a simple outage reset, a filter and airflow problem, or a fault in the powered equipment.
- If the system now heats normally, keep using it and monitor the next few cycles.
- If the only clear issue you found was a dirty filter, replace it and recheck temperature rise over the next hour.
- If the indoor blower runs but the outdoor unit never starts, schedule service for an outdoor electrical or control fault.
- If the outdoor unit tries to start but only hums, clicks, or trips the breaker, schedule service and do not keep forcing restarts.
- If the system runs but the air is just not warm enough, follow /heat-pump-air-from-vents-not-warm-enough.html.
- If airflow is weak in heat mode even with a clean filter, follow /heat-pump-airflow-weak-in-heat-mode.html.
A good result: If heat is back and stable, the problem was likely a reset, power interruption, or airflow restriction rather than a failed major part.
If not: If heat still does not return, the remaining likely causes are not good DIY part-swap jobs on a heat pump.
What to conclude: The safe homeowner repair path here is usually thermostat setup, breaker reset once, disconnect check, and filter correction. Beyond that, most outage-related no-heat faults move into electrical diagnosis or refrigerant-side service.
Stop if:
- You are considering replacing a capacitor, contactor, board, or compressor without testing.
- The system is your only heat in freezing weather and indoor temperatures are dropping fast.
- Any electrical fault, repeated breaker trip, or burned component is in play.
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FAQ
How long should I wait for a heat pump to restart after a power outage?
Give it at least 5 minutes after power and thermostat settings are correct. Many systems use a built-in delay to protect the compressor. Some take a little longer after unstable power.
Why is my heat pump blower running but the house is not warming up after the outage?
That usually means the indoor section has power but the outdoor section is not helping, or airflow is badly restricted. Check the outdoor breaker or disconnect, then check the filter and whether the outdoor unit is actually running.
Can a power outage damage a heat pump?
Yes, but a lot of post-outage no-heat calls turn out to be a tripped breaker, reset thermostat, or temporary lockout. If a breaker keeps tripping, the outdoor unit only hums, or you smell hot wiring, stop and call for service.
Should I replace the thermostat if the heat pump stopped heating after an outage?
Not first. Most of the time the thermostat just needs the right mode, a higher setpoint, fresh batteries, or a few minutes after power returns. Replace it only if you have clear evidence it is not sending a heat call.
What if emergency or auxiliary heat works but the heat pump does not?
That points away from a whole-house airflow problem and more toward the outdoor heat pump section, its power supply, or its controls. If backup heat works but the outdoor unit will not run, that is usually a service call.