Heat pumps are new to a lot of Sacramento-area homes, pushed along by SMUD rebates and the end of gas furnaces in new construction. They heat differently from a furnace, and the first winter with one produces a specific set of calls: the air is not hot enough, the outdoor unit is steaming, the thermostat says “aux” and the electric bill jumped. Some of that is normal. Some of it is a fault. Here is how to tell, in the order that finds the answer fastest.
First: what is normal and just feels wrong
- The air from the registers is warm, not hot. A furnace blows air at 120 to 140 degrees. A heat pump blows it at 90 to 105. The house reaches the same temperature; the air just feels milder on your hand. This is the number one “problem” we are called for, and it is not one.
- Steam or water off the outdoor unit, and a few minutes of cool air inside. Defrost. On a cold, damp morning frost forms on the outdoor coil; the unit reverses briefly to melt it, and the indoor air goes cool for two to ten minutes. In Sacramento’s foggy December this happens several times a morning. Normal.
- It runs for long stretches. A heat pump is designed to run long and steady at low output, not blast and stop like a furnace. Long run times are how it is efficient.
If what you are seeing is on this list, nothing is wrong. If it is not, keep going.
The six checks
- The thermostat mode. HEAT, not COOL, not EM HEAT. A heat pump thermostat set to “emergency heat” runs only the electric backup strips, which heats the house at roughly three times the cost and does not run the heat pump at all. If the display shows EM or a flame icon constantly, that is the first thing to fix.
- The filter. Heat pumps move more air than furnaces and are more sensitive to a clogged filter. Low airflow means the indoor coil cannot release its heat, the unit cuts output, and the strips come on to cover the gap. Check it, and check it again after smoke season.
- The outdoor unit. Is it running? Is it buried in leaves, fenced in too tightly, or coated in a sheet of ice rather than a light frost? Light frost that clears in defrost is normal. Solid ice that does not clear means defrost is failing, and that is a service call.
- The breakers. Two of them: one for the outdoor unit, one for the indoor air handler. A tripped outdoor breaker leaves the strips doing all the work; the house stays warm and the bill explodes. See our guide to why a heating bill is so high for what that costs.
- The condensate line, on attic units. Heat pump air handlers in the attic have a float switch in the drain pan. A clogged line shuts the system down exactly like a furnace. Standing water in the pan is the diagnosis.
- The reversing valve. If the system cools fine in summer but only blows cool air in winter, or the reverse, the valve that switches between heating and cooling may be stuck. Not a homeowner fix, but knowing the symptom saves diagnostic time.
The “aux heat” question
Most ducted heat pumps have electric resistance strips in the air handler as backup. They are supposed to run briefly: during defrost, when the thermostat is raised several degrees at once, or on the coldest nights. They are not supposed to carry the house every evening. If your thermostat shows “aux” or “auxiliary heat” for long stretches in normal Sacramento weather, one of these is true:
- The outdoor unit is not running at all, so the strips are the only heat. Check the breaker and listen for the fan.
- The system is low on refrigerant or has a failing component and cannot keep up, so the strips are covering the shortfall.
- The thermostat is configured wrong, with a balance point or aux lockout set for a colder climate than this one.
- The system is undersized for the house, which is rare here but happens with rushed installations.
Any of those is worth a visit, because strips running nightly can double a winter electric bill without the house ever feeling cold.
Where this shows up in the Sacramento area
Most heat pumps we service went in during the last five years, replacing gas furnaces under SMUD’s rebate in Elk Grove, Citrus Heights, Rancho Cordova, Folsom and the City of Sacramento, or under Roseville Electric’s program in Roseville. A meaningful share of the “not heating” calls on those systems trace back to how they were set up rather than to a failed part: thermostats left on furnace settings, aux lockouts never configured, or airflow never balanced after the furnace came out. Those are quick fixes, and they are why we commission every system we install rather than leaving it at the factory defaults. Our heat pump installation page covers what commissioning includes.
When to call and what it costs
If the outdoor unit is coated in solid ice, if aux heat runs for hours in mild weather, if the system will not start at all, or if it heats in summer but not winter, call. Diagnostic is a flat $69 across the Sacramento area, credited toward the repair. Same-day service in Roseville, Rocklin, Sacramento, Citrus Heights, Folsom and Elk Grove; our heat pump services page covers repair and maintenance. If you are still deciding whether a heat pump is the right replacement for a failing furnace, our guides to heat pump vs furnace and heat pump brands are the place to start.
Frequently asked questions
Why is my heat pump blowing cool air?
For a few minutes on a cold morning, it is in defrost, melting frost off the outdoor coil, and that is normal. If the air stays cool, check that the thermostat is on HEAT rather than COOL or EM HEAT, that the filter is clean, and that the outdoor unit is running. Warm rather than hot air at the registers is normal for a heat pump.
Why is there steam coming off my heat pump?
Defrost. The unit briefly reverses to melt frost from the outdoor coil, and the melting frost steams in cold air. It should last two to ten minutes and clear. A solid sheet of ice that never clears is a fault.
What does aux heat mean on my thermostat?
The electric backup strips are running. Briefly during defrost or a big setpoint change is normal. For hours in mild Sacramento weather is not; it usually means the outdoor unit is not running, the system cannot keep up, or the thermostat is configured for a colder climate. Strips cost about three times what the heat pump does to run.
Should I use emergency heat when it is cold?
Not in the Sacramento area. Emergency heat turns the heat pump off and runs only the electric strips. Modern heat pumps heat efficiently well below our winter lows. Use it only if the outdoor unit has failed and you are waiting for a repair.
How much does heat pump repair cost?
Our diagnostic is a flat $69 and comes off the repair. Thermostat configuration, a clogged condensate line or a defrost sensor are short visits. A reversing valve or a refrigerant leak costs more, and on a system under warranty the part is often covered.