No Heat After a Power Outage? 7 Steps to Get It Back

No heat after power outage problems happen when the power comes back but the furnace, boiler or heat pump does not restart on its own. A thermostat that lost its settings, a tripped breaker, a safety lockout or a built-in restart delay are the usual reasons. Nor'easters knock out power across the North Shore every winter, so here are 7 steps to get heat back safely.

Key Takeaways

• Give it a few minutes. Many systems wait before restarting.
• Check the thermostat. It may have reset to Off or default settings.
• Check breakers and switches. Surges can trip them.
• Never run a generator indoors. Carbon monoxide kills.

1. Wait a Few Minutes

• Heat pumps and many furnaces have built-in delays to protect the compressor and controls.
• Give the system 5 to 10 minutes after power returns.

2. Check and Reset the Thermostat

• Some thermostats reset to Off or lose their schedule after an outage.
• Set mode to Heat and raise the setpoint.
• Smart thermostats may need to reconnect to Wi-Fi.
• Battery thermostats may still have died if the outage was long.

Screen blank? See thermostat blank screen.

3. Check Breakers and Service Switches

• Check the breaker for the furnace, boiler or heat pump. Reset it once.
• Check the furnace or boiler service switch near the unit or at the basement stairs.
• For heat pumps, check the outdoor disconnect as well.

Power is back and the heat still is not? Request a no-heat repair visit and tell us what the system is doing.

4. Cycle Power to Clear a Lockout

• A power flicker can put a furnace or boiler into lockout.
• Turn the service switch off for 30 seconds, then back on.
• For oil burners, press the reset button once only.

5. Check Vents and the Outdoor Unit After a Storm

• High-efficiency furnaces and boilers vent through PVC pipes on the side of the house. Snow can block them and stop the system.
• Clear snow from heat pump outdoor units gently, without chipping ice.
• Check that the oil tank fill and vent are clear if you heat with oil.

Heat pump owners: see heat pump defrost mode explained for normal winter behavior.

6. Use a Generator Safely

• Never run a generator inside the house, basement or garage, even with doors open.
• The CDC recommends keeping generators at least 20 feet from the house, with the exhaust pointed away from windows and doors.
• Keep CO detectors working on every floor.
• Have an electrician install a transfer switch or interlock if you want to power the furnace or boiler. Never backfeed through an outlet.

7. Protect the House While You Wait

• Keep doors and curtains closed to hold heat.
• Drip faucets on outside walls if the house is getting cold.
• Never use an oven, grill or camp stove for heat.

See how to keep pipes from freezing without heat.

Why Some Systems Don't Restart

Power surges when the grid comes back can damage control boards, fuses and capacitors. A system that shows no lights at all after an outage may have a blown low-voltage fuse or failed board. That needs a technician. Furnace-specific steps are in furnace not turning on.

A clean, well-maintained system restarts more reliably. Per DOE's guide to furnaces and boilers, new condensing systems reach 90% to 98.5% AFUE; per DOE's maintenance checklist, a clean filter alone can cut energy use by 5% to 15%. As of 2026, many homeowners also add surge protection for HVAC equipment.

Get Heat Back After the Storm

No heat after a power outage is usually a thermostat reset, a tripped breaker, a lockout or a blocked vent. Work through these steps, keep generators outside, and call if the system shows no signs of life. For the complete checklist, see no heat in house.

Jose has worked in HVAC since 2015. HomePros gives a written flat price before any repair starts. Schedule heating repair, or call (781) 426-8428.