Before You Switch On Emergency Heat in a Seattle Home

EM heat usually means emergency heat, a backup mode found on some thermostats connected to heat-pump systems. Selecting it may bypass the normal heat pump and rely entirely on the property’s configured backup source. Before changing the setting in a Seattle home or rental, identify the equipment, distinguish EM from automatic AUX heat, and check the thermostat manufacturer’s instructions.

The short answer: EM means emergency heat

Emergency heat is intended as temporary backup when the primary heat pump has malfunctioned or been damaged. It is not normally a “heat the room faster” setting.

When EM heat is selected manually, the thermostat may stop calling on the outdoor heat pump and use only the backup source. Depending on the installation, that source could be electric resistance heat, a gas or oil furnace, hot water, or another configured system. An electric cooperative’s emergency-heat guide similarly distinguishes manually selected emergency heat from normal heat-pump operation and automatically activated supplemental heat.

Exact behavior varies. The official manual for the exact thermostat and heating equipment should determine what the label means and how the mode is operated.

Normal heat, AUX heat, and EM heat compared

The three terms describe different operating situations, although some manuals and interfaces use overlapping language.

Thermostat state	How it starts	What generally provides heat
Normal heat	Selected as the regular heating mode	The heat pump remains the primary source and moves heat into the home
AUX heat	Usually starts automatically	Supplemental heat assists when additional capacity or defrost support is needed
EM heat	Generally selected manually	The backup source may operate alone while the primary heat pump is bypassed

A brief AUX display does not necessarily indicate a failure. Supplemental heat may operate when the system needs additional heating capacity or while the outdoor unit completes a defrost cycle.

EM heat is different because the occupant generally selects it. If the backup source is electric resistance heat, backup-only operation can use more electricity than normal heat-pump operation. The actual bill effect depends on the equipment, energy source, operating time, weather, and utility rate, so the display alone cannot predict the cost.

Because some systems blur the terms “AUX,” “backup,” and “emergency” heat, use the table as an identification guide rather than a substitute for the model documentation.

First identify what kind of heating system you have

An EM heat label suggests that the thermostat may be configured for a heat pump, but it does not conclusively identify the equipment or its backup source.

Use this checklist:

• Photograph or write down the thermostat brand and model number.
• Check accessible indoor equipment labels without removing panels.
• Review the rental listing, owner’s records, inspection documents, or equipment paperwork.
• Look for an outdoor heat-pump unit if it is safely visible.
• Note whether the home also has a furnace, air handler, boiler, or other heating equipment.
• Search the manufacturer’s website for the manual matching the exact model number.

Heat pumps provide heating and cooling by moving heat rather than generating all indoor heat directly. That differs from a line-voltage thermostat controlling electric baseboard, fan-forced in-wall, self-contained hydronic baseboard, or in-ceiling radiant heat.

Seattle City Light includes those line-voltage systems in its thermostat-program information, but their inclusion does not mean a particular home has a heat pump or an emergency-heat mode. A wall control for electric baseboard or radiant heat should not be treated as a heat-pump thermostat without additional equipment information.

Use the manufacturer’s manual for any button sequence, including how to leave EM heat and return to normal heating. Instructions based only on a thermostat’s appearance or brand family could apply to a different model.

Use this decision path when the home feels cold

There is no universal outdoor temperature at which every Seattle occupant should switch on emergency heat. Heat pumps, backup sources, controls, and building conditions vary, so cold weather alone does not establish that EM heat is appropriate.

1. Read the display carefully. Determine whether it says EM or emergency heat, which is generally selected manually, or AUX or backup heat, which may have started automatically. Record any error code or warning symbol.

2. Check whether the property has electricity. Test a light or another simple electrical device elsewhere in the home. If the broader property appears to have lost power, check the electricity provider’s outage information and contact the host or property representative as appropriate. EM heat cannot repair or resolve a utility outage.

3. Identify the thermostat and heating system. Find the exact model manual and verify what the displayed label means for that system. Avoid operating instructions based only on the thermostat’s shape, color, or a similar-looking model.

4. Treat EM heat only as possible temporary backup. If the primary heat pump appears to have failed, model-approved emergency heat may provide temporary warmth while authorized service is arranged. It does not repair the underlying fault. Contractor guidance on when emergency heat may be appropriate likewise frames it as backup for a failed primary system rather than a routine response to cold weather.

5. Escalate an unresolved problem. If the home remains inadequately heated, EM heat stays on unexpectedly, or you cannot identify the equipment, contact the property’s responsible representative or a qualified HVAC technician.

Do not open equipment cabinets, touch electrical components, or attempt repairs based on a generic online video.

A checklist for renters and Seattle visitors

In a hotel-style unit, vacation rental, or leased home, the practical first step is usually to involve the host, landlord, or property manager before arranging repairs or making unfamiliar system changes.

Send a photo of the display and model number, describe whether the home has power and warm air, and say when the problem began. Ask for the property’s operating instructions or the exact manufacturer manual.

Where Seattle occupants can look for help

Seattle City Light customers can consult the utility’s heating and cooling resources for heating-system information, an Energy Advisor contact path, outage information, and contractor-discovery tools. City Light recommends obtaining at least three bids when a homeowner is considering a heating or cooling upgrade.

Use City Light for utility questions and contractor-discovery resources; use the equipment manual or a qualified technician for the thermostat itself.

Keep upgrade incentives separate from immediate troubleshooting. Rebate eligibility, equipment requirements, available funding, and program terms can change. Verify current conditions before selecting equipment or signing a contract.

Income-qualified Seattle homeowners and renters may also investigate the city’s HomeWise gas-to-electric and weatherization assistance. Depending on current eligibility and a home assessment, approved work may include conversion from a gas furnace to an electric heat pump. HomeWise is a longer-term improvement program, not an urgent thermostat or HVAC troubleshooting service.

For an immediate problem, identify the equipment and contact the person responsible for the property or a qualified technician. City Light and HomeWise can help with utility and longer-term improvement questions; neither replaces a repair visit.