A heat pump should be one of the cheapest ways to heat a home in Sacramento’s mild winters. When the electric bill jumps anyway, there is usually a specific reason, and the most common one shows up right on your thermostat.
The number one cause: backup heat running too much
Most heat pumps have electric resistance heat strips in the air handler. They are there for defrost cycles and for rare cold snaps when the heat pump alone cannot keep up. Resistance heat works like a giant toaster. It produces heat reliably, but it uses far more electricity per unit of heat than the heat pump itself.
In our climate, backup heat should run only occasionally. If it runs a lot, the bill shows it. Signs:
- Your thermostat shows AUX, AUX HEAT or EM HEAT frequently or for long periods
- The thermostat is set to Emergency Heat, which runs the strips instead of the heat pump
- The air from the vents is very hot rather than warm
- You smell a faint dusty or burning smell as the strips come on after sitting
Why backup heat runs too much
- Emergency heat left on. Someone switched to EM HEAT during a problem and forgot to switch back.
- Big setpoint jumps. Raising the thermostat several degrees at once, for example from a night setback, can make many thermostats bring in backup heat to recover quickly. Smaller steps, or a thermostat with smart recovery for heat pumps, avoid it.
- Thermostat not configured for a heat pump. A thermostat set up as if it were controlling a furnace, or without an outdoor lockout temperature for auxiliary heat, may call for strips unnecessarily.
- The heat pump is not carrying its share. Low refrigerant, a failing compressor, a stuck reversing valve or an iced coil all force backup heat to do the work. See heat pump freezing up and defrost explained.
Other causes
- Leaking attic ducts. Heated air escaping into the attic means longer run times. See duct sealing.
- A clogged filter or dirty coils.
- Short cycling. Frequent starts waste energy. See heat pump short cycling.
- An old heat pump losing efficiency with age.
- Rate changes. Time of use pricing means the same usage costs more during peak hours. Check your utility bill for the rate plan and when you use the most.
What you can do today
- Make sure the thermostat is on HEAT, not EM HEAT.
- Watch how often AUX shows during a normal day.
- Avoid large setpoint changes. Hold a steady temperature or change it by a degree or two.
- Replace the filter and clear the outdoor unit.
- Look at your utility’s online usage data to see which hours use the most.
What we do
We check the thermostat configuration and auxiliary heat lockout, measure how the heat strips are staging, verify the refrigerant charge and test the defrost controls. When the heat pump is doing its job, backup heat stays in the background. Our diagnostic is a flat $69 and it is credited toward the repair. If you are weighing an upgrade, see heat pump versus furnace and SMUD heat pump rebates. Our guide to high heating bills covers gas furnaces.
Frequently asked questions
Why is my heat pump electric bill so high?
The most common reason is electric backup heat strips running too often, from emergency heat left on, large setpoint changes, a thermostat not configured for a heat pump, or a heat pump that is not carrying its share.
What does AUX heat mean on my thermostat?
The electric backup heat is running. It should come on occasionally for defrost or cold snaps, not constantly in Sacramento’s mild climate.
Should I use emergency heat?
Only when the heat pump itself is not working. Emergency heat runs the electric strips instead of the heat pump and costs much more to operate.
Does turning my heat pump down at night save money?
Small setbacks can. Large ones may cost more if the thermostat uses backup heat to recover in the morning. Smaller changes or a heat pump aware thermostat help.
Can leaking ducts raise my heat pump bill?
Yes. Heated air lost into the attic means the system runs longer to keep the house warm.
Is a heat pump cheaper to run than a gas furnace in Sacramento?
It can be, because the climate is mild and heat pumps are efficient. The real comparison depends on your electric and gas rates and whether backup heat is running too much.