Usually not
Most heat pump replacements in Memphis reuse the circuits that are already there.
The outdoor unit takes over the AC’s circuit, and the air handler takes over the furnace’s. The breaker might change size to match the new nameplate, but the wire, the panel and the service usually stay exactly as they are.
We check before we quote
Bluffline Memphis Heat Pumps checks the panel, the breakers and the wire on the first visit, and lists any electrical change as its own line on the estimate.
When work is more likely
| Job | Electrical change likely? |
|---|---|
| Heat pump replacing a heat pump | Rarely; existing circuits usually fit |
| Heat pump replacing an AC, furnace kept (dual fuel) | Rarely; outdoor circuit reused |
| Electric furnace to heat pump | Rarely; strips get smaller |
| Gas furnace to all-electric heat pump | Often a new strip-heat circuit |
| Adding a second system | A new circuit for each half |
Reading a nameplate
Every outdoor unit and air handler has a nameplate with two electrical numbers that decide the circuit.
Minimum circuit ampacity
The smallest wire size, in amps, that can safely feed the unit. The wire has to be rated at least this.
Maximum overcurrent protection
The largest breaker allowed. The breaker can be smaller, down to what the unit needs to start, but not bigger.
What that means for reuse
If the old circuit’s wire meets the new unit’s minimum ampacity and its breaker is within the maximum, the circuit can stay. Many 3-ton heat pumps fit the circuit a 3-ton AC used. A larger or different unit may not.
Strip heat is the big load
The electric strips in an air handler are by far the largest electrical load in a heat pump system. A 10 kW kit draws about 42 amps at 240 volts; a 15 kW kit about 63; a 5 kW kit about 21.
Electric furnace to heat pump
An electric furnace with 15 kW of strips already has a large circuit. A heat pump with 5 or 8 kW of backup draws less from it. That is why electric furnace to heat pump swaps rarely need a panel upgrade, and sometimes free up capacity.
Gas to electric
A gas furnace draws a few amps at 120 volts for its blower and controls. Replacing it with an air handler and strips adds a new 240-volt circuit the house never had. That is where panels run out of space or capacity. The gas furnace to heat pump page covers that conversion.
Sizing strips to protect the panel
Strips should be sized to the house’s actual need at Shelby County’s 20-degree design temperature, not to the biggest kit the air handler accepts. Many Memphis houses need 5 to 10 kW with a correctly sized heat pump.
Why it matters
- Smaller strips mean a smaller breaker and less load on the service.
- A lockout that keeps strips off above about 30 to 35 degrees means they rarely run at all.
- Staged strips, where the kit comes on in steps, limit the peak draw.
The aux and emergency heat guide explains staging and lockouts.
Older panels and 100 amp services
Many older Memphis houses and West Memphis ranches have 100 amp services. A load calculation adds up the house’s large loads to see whether the service can carry the new equipment.
What the calculation counts
- The range and oven, the dryer and the water heater if electric.
- The heat pump and its strips, at their nameplate ratings.
- Other large loads: a pool pump, a well pump, a workshop, an EV charger.
Panels worth a closer look
Some older panel brands and models have known problems. If your panel is rusted, overheated, full of double-tapped breakers or out of spaces, a licensed electrician should look at it whatever happens with the heat pump.
Signs worth mentioning on the visit include warm breakers, a burning smell near the panel, lights that dim when the AC starts, or breakers that trip without an obvious cause.
A West Memphis example
A 1968 brick ranch in West Memphis has a 100 amp panel, a 1999 electric furnace and an AC. The owners want a heat pump. Here is how the electrical side works out:
| Item | Old system | New system |
|---|---|---|
| Backup or furnace strips | 10 kW electric furnace | 5 kW strip kit |
| Indoor circuit | Large furnace circuit | Same circuit, re-breakered to the new nameplate |
| Outdoor circuit | AC circuit | Reused; fits the new unit’s ratings |
| Panel change | None | None |
Why it worked
The house’s heat loss at 20 degrees, with a correctly sized 2.5-ton heat pump, left a gap 5 kW could cover.
A 10 kW kit would have pushed the service calculation past what the panel could safely carry with the range, dryer and water heater. Sizing the strips to the real need kept the panel as it was. Our West Memphis page tells the rest of the job.
The outdoor disconnect
Every outdoor unit needs a disconnect switch within sight of it, so it can be shut off safely for service. When a unit is replaced, the old disconnect often stays if it is sound and rated for the new unit.
When it changes
- Rust or corrosion inside the box, common after 15 or more Memphis summers.
- A fused disconnect whose fuses don’t match the new unit’s rating.
- A moved pad, where the disconnect has to stay within sight of the unit.
Surge protection
Heat pumps have electronic controls, and variable speed units have inverter boards. A surge protector at the disconnect or the panel is inexpensive insurance in a region with summer thunderstorms. It is optional, and it goes on the estimate as its own line if you want one.
Ways to avoid an upgrade
When a panel is close to its limit, there are options short of a new service:
- Smaller strips, sized to the real need.
- Dual fuel, keeping a gas furnace as backup instead of strips.
- Load management devices that keep the strips and another large load from running together.
- A variable speed heat pump, which carries more of the winter on its own at lower draw.
Generators and outages
If you plan a standby generator, strip heat changes its size. A gas furnace’s blower needs a small generator; 10 kW of strips needs a large one. The ice storm guide covers outage planning.
Who does the work
Panel and circuit work is done by a licensed electrician, with the permit your town requires.
It is listed on the estimate as its own line, with its own price, so you can see what it adds. The cost page has the typical ranges for the heat pump itself.
Questions to ask
Before you sign, ask:
- Does the existing circuit’s wire and breaker fit the new unit’s nameplate?
- What strip size does the load calculation call for?
- Does the panel have room for any new breaker?
- Is a load calculation on the service needed, and what does it show?
The sizing guide explains how the strip size is chosen, and the Memphis buying guide puts the whole decision in order.