# Dual fuel heat pump installation in Memphis

> Keep your gas furnace and put a heat pump where the AC was. Dual fuel heat pumps in Memphis, sized from a load calculation and set for MLGW rates.

URL: https://blufflinememphisheatpumps.com/dual-fuel-heat-pump/

Service

A heat pump in place of your AC, on top of the gas furnace you keep, with the handoff set for MLGW rates.

(901) 657-2200

Last Updated: November 12, 2026

1 visit

before a written estimate with load numbers, model numbers and price

95° / 20°

Shelby County design temperatures we size for

In writing

start-up readings for charge, airflow and backup heat

## Your AC quit and the furnace is fine

Put a heat pump where the AC was and keep the gas furnace for the coldest hours. That is a dual fuel system, and for a Memphis house with a sound furnace it is usually the first option [Bluffline Memphis Heat Pumps](https://blufflinememphisheatpumps.com/) prices.

### What you get

- **Summer:** the heat pump cools exactly as an AC would.
- **Winter:** it heats until the outdoor temperature drops to a switchover point you choose, then the thermostat hands heating to the furnace.
- **Always:** two heat sources instead of one, and a furnace that still has years in it stays in service.

Most of the houses this fits heat with MLGW gas. In Germantown about two-thirds of homes do, and in Collierville and Bartlett well over half, according to the Census Bureau’s American Community Survey. Our [Germantown page](https://blufflinememphisheatpumps.com/service-areas/germantown/) covers the local side, including where a 1980s furnace and a newer AC tend to stand.

## What gas and electricity cost here

On MLGW’s current rates, gas heats more cheaply per BTU than a heat pump. That is the honest starting point, and it changes how we set a dual fuel system.

Per million BTU of delivered heat, worked from MLGW’s published residential rates:

- **Gas in a 95 percent furnace:** about $6.30
- **Heat pump, mild day:** about $10.20
- **Heat pump, cold day:** about $14.30
- **Electric strips:** about $35.80

The full comparison is in [gas furnace or heat pump in Memphis](https://blufflinememphisheatpumps.com/guide/heat-pump-vs-gas-furnace-memphis/). The gas side moves, though. MLGW’s purchased gas adjustment changes every month, and in February 2026 it pushed gas to roughly $12.17 per million BTU. In a month like that, the heat pump is the cheaper heat on mild days.

### So where does the switchover go?

It is your call, and we set it with you:

- **Comfort first.** Run the heat pump down to about 35 degrees. Heat pump air is steadier and quieter on mild days, at a small extra cost on today’s rates.
- **Cost first.** Set the switchover high and let gas carry nearly all of winter. The heat pump becomes the AC and the backup.
- **Somewhere between.** A setting between 30 and 40 degrees, moved up when the gas adjustment drops and down when it jumps.

An outdoor sensor makes the handoff automatic. We show you the one setting that moves it, and the [switchover guide](https://blufflinememphisheatpumps.com/guide/dual-fuel-switchover-temperature/) works through the numbers.

## What we check before we promise anything

A heat pump sits on the furnace, so the furnace has to be up to it. On the first visit we look at three things.

### The heat exchanger and flue

We inspect the furnace’s heat exchanger and venting and take a combustion reading. A cracked heat exchanger or a failing flue changes the answer to a [gas furnace to heat pump](https://blufflinememphisheatpumps.com/gas-furnace-to-heat-pump/) conversion instead.

### The blower

A heat pump needs about 400 cubic feet of air per minute for each ton. Older furnace blowers sometimes can’t deliver that at a speed that works, and if yours can’t, the estimate says so rather than leaving the heat pump starved for air.

### The fit

The new coil sits on top of an upflow furnace. In a closet with a low ceiling, we may need a short sheet-metal transition, and the coil has to match the outdoor unit as a rated pair.

## Sizing it for the house

We size the heat pump from a load calculation, not from the old AC’s nameplate. Memphis houses were often fitted with more capacity than they needed, and new windows or attic insulation shrink the load further.

Shelby County’s design conditions are 95 degrees in summer and 20 degrees in winter. With a furnace covering the coldest nights, a heat pump sized for the cooling load is usually the right size.

### Why bigger is worse here

An oversized unit short-cycles and leaves the house clammy, the opposite of what you want through a Memphis July. [How sizing works](https://blufflinememphisheatpumps.com/guide/heat-pump-sizing-manual-j/) explains the method.

## What the job includes

Most dual fuel installs take one day, because the furnace, its venting and most of the ductwork stay as they are:

1. Pull the mechanical permit for your town.
2. Recover the refrigerant from the old AC and remove it and its coil.
3. Set the matched coil on the furnace and the heat pump on a raised pad.
4. Braze the line set under nitrogen, pressure-test it and pull a vacuum below 500 microns.
5. Charge by weight and verify against the maker’s numbers.
6. Wire the dual fuel thermostat and outdoor sensor, and set the switchover.
7. Test cooling, heating, defrost and the gas handoff, and write the readings down for you.

If the existing line set is the right size and holds pressure, we flush and reuse it. If it is undersized, damaged or buried somewhere we can’t verify, we replace it.

## What it costs

Bluffline’s typical range for a dual fuel heat pump added to an existing gas furnace is $5,000 to $10,000. Your written estimate after the site visit sets the price.

The number moves with the heat pump’s size and efficiency tier, whether the coil needs a transition, line set length and condition, and any duct or electrical work. A variable speed heat pump sits near the top of the range. The [cost guide](https://blufflinememphisheatpumps.com/heat-pump-installation-cost/) covers every driver.

### Rebates

TVA EnergyRight pays $800 for qualifying heat pumps rated 17 SEER2 or higher and $500 at 15 SEER2, when a participating contractor in TVA’s Quality Contractor Network installs the equipment. The federal 25C tax credit ended for equipment installed after 2025. See [how the TVA rebate works](https://blufflinememphisheatpumps.com/guide/tva-energyright-heat-pump-rebate/).

## When dual fuel isn’t the right answer

Dual fuel isn’t always the right call, and we will say so on the estimate:

- **The furnace is failing.** A cracked heat exchanger or a furnace near the end of its life makes [all-electric](https://blufflinememphisheatpumps.com/gas-furnace-to-heat-pump/) or a new furnace the better comparison.
- **You only ever want gas heat.** A new AC is simpler and cheaper, and on today’s MLGW rates it heats no worse.
- **The house heats with strips.** Then there is no furnace to keep, and an [electric furnace to heat pump](https://blufflinememphisheatpumps.com/electric-furnace-to-heat-pump/) swap is the job.

For the whole decision in order, start with the [Memphis heat pump buying guide](https://blufflinememphisheatpumps.com/guide/memphis-heat-pump-buying-guide/).

## What's included

- Load calculation for the whole house
- Furnace check (heat exchanger, flue, blower airflow)
- Heat pump and matched coil on the existing furnace
- Line set flushed and reused, or replaced
- Raised pad and electrical disconnect
- Dual fuel thermostat with an outdoor sensor
- Switchover temperature set with you
- Old refrigerant recovered and old equipment hauled away
- Start-up readings in writing

## AC swap, dual fuel or all-electric

|  | New AC only | Dual fuel | All-electric heat pump |
| --- | --- | --- | --- |
| Cooling | New AC | Heat pump | Heat pump |
| Heating | Gas furnace | Heat pump, then gas below the switchover | Heat pump, then strips below its range |
| Second heat source | No | Yes, gas and heat pump | Strips only |
| Furnace | Kept | Kept | Retired, gas capped |
| Usual fit | You only ever want gas heat | Good furnace, failed AC | Failing furnace, or no gas wanted |

## A typical Germantown dual fuel job

A 1984 two-story in the Farmington area with an eight-year-old gas furnace and a 4-ton AC whose compressor failed in July. The owners want cooling back the same week and don't want to replace a furnace that works, so we price a straight AC swap beside a dual fuel system on one estimate.

Where

Germantown, Farmington area

The house

1984 two-story, about 2,600 sq ft, one system for both floors, furnace in a closet off the garage

Price

$8,200

Time on site

1 day

1. Check the furnace first The heat exchanger, flue and blower all pass. The blower can deliver about 1,400 CFM at a usable speed, which a 3.5-ton heat pump needs, so dual fuel is on the table.
2. Size from the house The load calculation comes in at 3.5 tons, half a ton under the old AC. Newer windows and attic insulation explain the difference.
3. Set the coil and the outdoor unit We recover the old refrigerant, set a matched 3.5-ton cased coil on the furnace with a sheet-metal transition to clear the closet ceiling, and put a 16 SEER2 heat pump on a new raised pad in the east side yard.
4. Prove the line set The existing 3/8 by 7/8 inch line set is flushed, brazed under nitrogen, pressure-tested and pulled below 500 microns before we charge by weight and check subcooling.
5. Set the handoff The owners want steadier heat on mild days, so the heat pump runs down to 35 degrees and gas takes over below that. We test defrost and the gas handoff and leave the readings in writing.

## Related resources

- [Learn**What switchover temperature should a dual fuel heat pump use in Memphis?** The two numbers behind the setting, what MLGW's rates say about them, and how to pick a point you can live with.](https://blufflinememphisheatpumps.com/guide/dual-fuel-switchover-temperature/)
- [Decision Guide**Is a heat pump or a gas furnace cheaper to run in Memphis?** The per-BTU math on MLGW's rates, the months it flips, and what it means for keeping, adding to or retiring a furnace.](https://blufflinememphisheatpumps.com/guide/heat-pump-vs-gas-furnace-memphis/)
- [Learn**How should a heat pump thermostat be set up in Memphis?** The handful of settings that decide whether a heat pump saves money: the equipment type, the outdoor sensor, the lockout, setbacks and the fan.](https://blufflinememphisheatpumps.com/guide/heat-pump-thermostat-setup/)
- [Learn**What happens to a heat pump in an ice storm or a power outage?** Ice on the unit, power out for a day, and what to do before, during and after. Plus how gas, strips and generators compare.](https://blufflinememphisheatpumps.com/guide/heat-pump-ice-storm-power-outage/)
- [Decision Guide**How do you buy the right heat pump for a Memphis house?** The whole decision in the order you meet it, from the system you have now to the readings you should get at start-up.](https://blufflinememphisheatpumps.com/guide/memphis-heat-pump-buying-guide/)

## How a job runs

### Call or send the form

Tell us what heats and cools the house now and what's going wrong.

### One visit

We look at the equipment, ducts, panel and the spot outside and run the load numbers.

### Written estimate

Load figures, matched model numbers, scope and price on one page.

### Install and start-up

Permit pulled, system set, line set tested, and the start-up readings handed to you.

## Dual fuel heat pumps: questions

### What temperature should a dual fuel system switch to gas in Memphis?

On MLGW's current rates gas is the cheaper heat at any outdoor temperature, so the switchover is a comfort choice. A setting between 30 and 40 degrees gives steadier heat on mild days; set it higher if you want gas to carry nearly all of winter.

### Can any gas furnace work with a heat pump?

Most can, but the blower has to move enough air for the heat pump's size and the coil has to fit above or below the furnace. We check both on the first visit, along with the heat exchanger and flue.

### Does a dual fuel system qualify for the TVA rebate?

The heat pump can, if it is rated 15 SEER2 or higher and a participating contractor in TVA's Quality Contractor Network installs it. The estimate shows which tier the equipment you choose falls in.

### What happens to dual fuel heat in a power outage?

Both sides stop. The heat pump needs power, and a gas furnace still needs power for its blower, igniter and controls. A small generator sized for the furnace can keep gas heat running.

### How long does a dual fuel installation take?

Usually one day when the furnace, its venting and most of the ductwork stay as they are. Duct work or a new circuit can add a second day.

## Related services

- [Service**Heat pump replacement** Your heat pump is near the end and you want the next one to last. We size it from the house and match both halves.](https://blufflinememphisheatpumps.com/heat-pump-replacement/)
- [Service**Gas furnace to heat pump** Going all-electric means retiring the furnace and capping its gas line. We show you when that pays and when keeping gas is smarter.](https://blufflinememphisheatpumps.com/gas-furnace-to-heat-pump/)
- [Service**Air handlers** The indoor half decides airflow, drainage and backup heat. We replace it with a matched unit and keep a sound outdoor unit.](https://blufflinememphisheatpumps.com/heat-pump-air-handler-replacement/)

## Get an estimate for dual fuel heat pumps

Tell us what heats and cools the house now, what's going wrong and roughly where the house is. Photos of the outdoor unit and its nameplate help.

(901) 657-2200