QUOTE LINE ITEM · LAST CHECKED NOVEMBER 4, 2026
Backup heat and auxiliary heat strips on a heat pump quote: what it should say
Quick answer
A quote should say what heats the house when the heat pump alone can’t keep up: electric resistance “aux” strips (and their size), your existing furnace or boiler, or nothing because the heat pump is sized for your coldest days. It should also say how the controls decide when backup heat runs.
What a complete quote states
- The backup source, if any: electric strip size in kW, or which existing system stays.
- The heat pump’s rated capacity at low outdoor temperatures (cold-climate models list this).
- How the thermostat or controls switch to backup heat, and at what outdoor temperature (lockout or balance point).
- The electrical circuit for any heat strips, and that it is included.
Red flags when it is missing or vague
- Large heat strips included “for safety” with no explanation of how often they will run.
- No mention of backup heat in a cold climate, and no low-temperature capacity given.
- Keeping the furnace with no plan for how the two systems are controlled.
- A thermostat that isn’t compatible with the heat pump’s staging or the backup.
Three questions to send the installer
- What provides heat when the heat pump can’t keep up on its own, and how large is it?
- At what outdoor temperature will backup heat start, and how is that set in the controls?
- How much heat does the proposed heat pump deliver at my area’s coldest design temperature?
Why two quotes differ here
Electric resistance strips turn one unit of electricity into one unit of heat, while a heat pump in moderate weather moves more heat than the electricity it uses, so strips that run often raise bills. A quote with a smaller heat pump and big strips can look cheaper on paper than one with a larger cold-climate unit. Keeping an existing furnace (a “dual-fuel” or hybrid setup) changes the price again. These are different designs, not different prices for the same thing.
Controls matter as much as hardware. Ask each installer how the system decides when to use backup heat. A poor setting can make the strips run when the heat pump could handle the load.
What the sources say
A DOE-funded permitting checklist cites the residential energy code (IECC R403.1.2): heat pumps with electric resistance backup need controls that, “except during defrost, prevent supplemental heat operation when the heat pump compressor can meet the heating load.”
ENERGY STAR’s cold-climate criteria require a coefficient of performance of at least 1.75 at 5°F and heating capacity at 5°F of at least 70% of the capacity at 47°F, which is why cold-climate models list low-temperature output.
Programs differ on backup: Efficiency Maine says a furnace or boiler can stay for emergency backup but its capacity “cannot be counted” toward sizing; NYS Clean Heat limits electric resistance to 10% of the building heating load on some projects; and Mass Save’s rebate form asks for the integrated control’s switchover temperature. A DOE-funded field study of cold-climate heat pumps found that large morning thermostat setbacks caused “excessive auxiliary heat use.”
Cost
We don’t publish a price for backup heat. Ask each installer for the strip size and its circuit as separate lines.
Sources
- Heat Pump Space Heating Permitting & Inspection Checklist (PDF) (New Buildings Institute for the U.S. DOE, page dated October 2024)
- Air-source heat pumps key product criteria (ENERGY STAR)
- Residential cold-climate heat pump technology challenge (PDF) (PNNL, DOE peer review, page dated November 2024)
- Sizing and selecting air-source heat pumps in cold climates (PDF) (NEEP)
- NYS Clean Heat Program Manual v2 (PDF) (NYS Clean Heat, page dated March 5, 2026)
- Residential heat pump claim form (PDF) (Efficiency Maine)
- Mass Save 2026 air-source heat pump rebate form (PDF) (Mass Save sponsors, page dated 2026 installs)
Holding two or three quotes? Mark Equipment as Included, Excluded or Unclear for each quote and get one question list per installer. Nothing is uploaded.
Last checked: . Informational only. This is not financial, tax, legal or professional installation advice, and we do not verify any installer’s work.