How a heat pump works
A heat pump is a central air conditioner that can run in reverse. This guide from Bluffline Memphis Heat Pumps starts there, because the rest follows from it.
In summer it pulls heat out of the house and dumps it outside, exactly as an AC does. In winter a reversing valve flips the refrigerant’s direction, so the outdoor coil gathers heat from the outdoor air and the indoor coil releases it into the ducts.
Why it is efficient
Because it moves heat rather than making it, a heat pump delivers two to four units of heat for each unit of electricity, depending on the weather. Resistance strips deliver one. That ratio, the coefficient of performance, falls as the outdoor air gets colder, which is why every heat pump needs a plan for the coldest hours.
The parts you will hear about
- Outdoor unit: the compressor, the outdoor coil and the fan.
- Air handler or coil: the indoor half, either a full air handler with backup strips or a coil sitting on a gas furnace.
- Line set: the two copper refrigerant lines that join them.
- Reversing valve: the part that switches between cooling and heating.
- Thermostat: the controls that stage the heat pump, the backup and, on dual fuel, the gas handoff.
Start with what you have now
What heats the house today decides the job, the price and what happens to the bill afterward. In Memphis that comes down to three starting points, and we handle all three.
Electric strip heat
More than half of Memphis homes heat with electricity, according to the Census Bureau’s American Community Survey. Where that means an electric furnace with resistance strips, a heat pump cuts the heating part of the bill the most. See electric furnace to heat pump.
A gas furnace
About 42 percent of Memphis homes heat with MLGW gas, and in Germantown and Collierville it is over 60 percent. If the furnace is sound, a dual fuel heat pump on top of it is usually the first option worth pricing.
An old heat pump
If the house already has a heat pump, the question is whether to repair it or replace it, and how much of the system to change. Heat pump replacement covers that job.
Gather your house’s numbers before anyone visits
Ten minutes of homework makes every quote better and faster. Before the first visit, collect:
- Photos of the nameplates on the outdoor unit, the air handler or furnace, and the electrical panel.
- A year of MLGW bills, or the usage history from your MLGW account, so winter and summer use can be compared.
- The house’s age and rough square footage, and any changes since it was built: new windows, attic insulation, an addition.
- A short comfort log: which rooms run hot or cold, when the house feels damp, and when the bills spike.
The nameplates tell an installer the age, size and refrigerant of what you have. The bills show whether winter or summer drives your costs, which points to strips, gas or a duct problem.
Decide what you want from it
Write down what you want the new system to fix before anyone quotes. It keeps quotes comparable and tells the installer what to measure.
Common goals in Memphis houses:
- Lower winter bills. Real when replacing strips; small or none when replacing gas on today’s MLGW rates.
- A drier house in summer. Sizing, airflow and duct sealing matter more here than the label.
- Even temperatures upstairs. Usually a duct and return problem, sometimes a case for a second system.
- A second heat source. Dual fuel gives you gas and a heat pump.
- Gas out of the house. An all-electric conversion, with a strip kit sized for the coldest nights.
Size it from the house
A heat pump should be sized from a load calculation, not copied from the old unit’s nameplate. The calculation counts the walls, windows, insulation, air leakage and orientation of your house room by room.
Memphis design conditions
Load calculations use a summer and a winter design temperature for the location. ENERGY STAR’s reference guide lists 95 degrees for summer and 20 degrees for winter in Shelby County, from the Millington weather station. The heat pump is sized for those conditions, not for the rare record day.
Why oversizing hurts here
An oversized system cools the air quickly and shuts off before it has pulled the water out of it. In a Memphis July that leaves the house cool and clammy. It also short-cycles, which wears the equipment.
The right size is often smaller than the unit being replaced, especially after new windows or attic insulation. How heat pump sizing works walks through the method.
Check the ducts it has to breathe through
A ducted heat pump can only deliver what the ducts let through. A heat pump needs roughly 400 cubic feet of air per minute for each ton, which is often more than an old system was moving.
What to have measured
- Static pressure across the system, against the maker’s limit.
- Return size, because one small return can starve the whole house.
- Supply temperatures room by room.
- Duct condition in the crawlspace or attic: seams, insulation and crushed runs.
Crawlspaces and attics
Many Memphis houses run ducts through a crawlspace. In humid summer air, a poorly insulated supply duct sweats and a leaky return pulls damp air in. Attic ducts gain heat instead. Either way, a new heat pump on bad ducts underperforms. See crawlspace ductwork.
Choose dual fuel or all-electric
On MLGW’s current rates, gas heats cheapest per BTU, strip heat costs the most, and a heat pump sits between them. That one fact settles most of this decision.
| What heats the house | Dollars for each million BTU delivered |
|---|---|
| Resistance strips | 35.80 |
| Heat pump below freezing | 14.30 |
| Heat pump on a mild day | 10.20 |
| High-efficiency gas furnace | 6.30 |
We work these out from MLGW’s tariff sheets, fuel and gas adjustments included and the monthly service charges left aside. The adjustments shift every month: during February 2026, gas briefly cost about $12.17 for the same heat.
What the numbers mean
- Strip-heat house: a heat pump is the clear move. The savings are large.
- Gas house with a good furnace: dual fuel. The heat pump replaces the AC and gives you a second heat source; you set when gas takes over.
- Gas house with a failing furnace: compare a new furnace and AC, dual fuel with a new furnace, and all-electric on one estimate. See gas furnace to heat pump.
The gas furnace or heat pump guide turns these figures into yearly costs, and the switchover guide covers where a dual fuel system should hand off to gas.
Plan for humidity
A Memphis heat pump spends as much of its summer effort on water as on heat. Comfort at 72 degrees depends on keeping indoor humidity near 50 percent.
What helps most:
- Right sizing, so the system runs long enough to dehumidify.
- Airflow set for dehumidifying at start-up, rather than the factory setting.
- Sealed returns, so damp crawlspace or attic air stays out.
- Variable speed equipment, which runs longer at low speed. See variable speed heat pumps.
Our humidity guide goes deeper.
Backup heat: strips, gas or both
Every heat pump in Memphis needs a plan for the coldest hours. Output falls as the outdoor temperature drops, while the house loses heat faster, and the two lines cross at what installers call the balance point.
Electric strips
In an all-electric system, a strip kit in the air handler helps below the balance point. Sized correctly and locked out above a set temperature, strips run only on the coldest mornings. Oversized and left without a lockout, they run whenever the thermostat asks for a big jump, and the bill shows it.
Gas
In a dual fuel system, the furnace takes over below the switchover temperature you choose. On MLGW’s rates gas is the cheaper heat, so the switchover is a comfort and redundancy choice rather than a savings one.
What to ask
Ask the installer what strip size or switchover they propose, why, and at what outdoor temperature the backup will start. See auxiliary and emergency heat.
Pick the equipment tier
Efficiency labels tell you how much heat or cooling you get for the electricity. They don’t tell you whether the system will be comfortable in your house.
The labels
SEER2 rates seasonal cooling efficiency and HSPF2 rates seasonal heating efficiency, both under the current federal test procedure. Higher numbers cost more and save more. SEER2 and HSPF2, explained covers what each tier buys.
Single-stage, two-stage or variable speed
- Single-stage: full output or off. Lowest price; fine in a well-sized system on good ducts.
- Two-stage: a low stage for most hours. A good middle ground for humidity.
- Variable speed: matches output to the load. Best humidity control and the quietest outdoor unit, at the highest price.
Match the indoor half
The outdoor unit has to be paired with a matched coil or air handler to deliver its rating. A quote that reuses an old, mismatched indoor coil looks cheaper and delivers less.
Check the panel and the outdoor spot
Two practical checks decide whether the install day goes smoothly. Both belong on the first visit.
The electrical panel
A heat pump with a strip kit needs two double-pole breakers and enough capacity on the main service. Older Memphis houses can run short on panel space. Have it checked before the quote, so any circuit or panel work is on the estimate. See panel space for a heat pump.
The outdoor unit
The outdoor unit needs the maker’s clearances, a level, raised pad and a spot away from bedroom windows where the lot allows. Memphis ice storms make the raised pad more than a detail: it lets ice and meltwater drain during defrost. See placement and noise and ice storms and outages.
Repair or replace an old heat pump
If the house already has a heat pump, the first decision is whether it is worth fixing. Age alone doesn’t settle it; the failure and the refrigerant do.
- Small parts on a mid-life unit: a capacitor, contactor or fan motor on a unit under about ten years is a repair.
- A failed compressor or a large leak on an old unit: usually a replacement, especially on R-22, which is no longer produced and keeps getting more expensive to recharge.
- A mismatched or failing indoor half: a newer outdoor unit with a rusted air handler can be an air handler job alone.
Ask for the repair and the replacement priced on the same visit. See repair or replace and heat pump lifespan in Memphis.
Who does the work
Tennessee’s Board for Licensing Contractors requires a state contractor license with an HVAC classification for projects of $25,000 or more; smaller residential jobs fall under local rules, and the permit office checks who pulls the permit. Mississippi and Arkansas have their own boards.
Questions that tell you more than a logo
Whoever installs your system, ask whose name will be on the permit, whether the installer is in TVA’s Quality Contractor Network if you want the rebate, and what the start-up readings will include. Those three answers tell you more than a logo.
Permits in your town
Every heat pump installation needs a mechanical permit and an inspection. Which office issues it depends on the town:
| Town | Permit office |
|---|---|
| Memphis, Germantown | Memphis and Shelby County Office of Construction Code Enforcement |
| Millington | Shelby County, applied through Develop901 |
| Bartlett | City of Bartlett Code Enforcement |
| Collierville | Town of Collierville Building and Codes |
The installer pulls the permit. The install day can’t come before the permit is issued, which sets part of the calendar.
Rebates
TVA EnergyRight is the program paying on heat pumps here today. Equipment from 15 SEER2 earns $500 and from 17 SEER2 earns $800, claimed through your power company once a contractor in TVA’s Quality Contractor Network installs it.
Two other sources are out: the federal 25C credit stopped with equipment placed in service after December 31, 2025, and the state’s federally funded rebates are still waiting to open. See how the TVA rebate works.
Compare quotes line by line
A fair heat pump quote lists more than a total. Put these questions to every installer:
- What did the load calculation say, and what size follows from it?
- Which outdoor and indoor models, and are they a rated pair?
- Are duct, electrical and access work priced on separate lines?
- Is the line set reused or new, and why?
- Are the permit, refrigerant recovery and haul-away included?
- Which TVA rebate tier does the equipment reach?
- Which readings will you hand over at start-up?
When two quotes sit thousands apart, the answers usually show they price different work. Our cost guide has Bluffline’s typical ranges for each type of job.
What a good install day looks like
A careful install is mostly invisible, so ask what will be done and what you will get afterward. The steps that matter most:
- Old refrigerant recovered, not vented.
- The line set brazed under nitrogen and pressure-tested.
- A vacuum pulled below 500 microns and held, to prove the system is tight and dry.
- Charge set by weight and checked against the maker’s numbers.
- Static pressure, airflow and temperature split measured.
- Defrost, backup strips and any gas handoff tested on purpose.
You should get those readings in writing. The installation checklist explains each one.
Commercial buildings
Small offices, shops and churches follow the same logic, plus rooftop units, crane lifts, ventilation needs and work scheduled around business hours.
Bluffline’s typical range for replacing a light commercial packaged heat pump is $9,000 to $22,000 per unit. See commercial heat pump installation.
How long it takes
From the first call to a working system usually runs one to two weeks. The visit and written estimate take a few days, the permit has to be issued before install day, and most installs take one or two days on site.
- One day: an outdoor unit swap, or dual fuel on a sound furnace.
- Two days: a full system with a new air handler, or a strip-heat conversion with new circuits.
- Three days: a conversion with duct work, or two systems.
If the AC has failed in July, say so when you call; the estimate can note which equipment is available soonest, and a straight replacement of the same type is usually the quickest to schedule.
After it’s in
A heat pump stays efficient when it can breathe. Change the filter on schedule, keep two feet clear around the outdoor unit, and rinse the coil each spring.
Learn the difference between aux and emergency heat on the thermostat, and leave the installer’s settings alone unless you know why you are changing them. See auxiliary and emergency heat and thermostat setup.