IECC climate zone
Zone 4A — Mixed – Humid
Mid-Atlantic, Virginia, Tennessee, Missouri, coastal New Jersey.
Winter design temp
14°F
Heating degree days
4,500
Cooling degree days
1,300
Summer design temp
91°F
What to install here
The genuine crossover zone. A modern variable-speed heat pump covers the year, but a few nights a season will approach its limits. Either a cold-climate model or a properly configured backup heat source makes the difference between comfortable and expensive.
What "winter design temperature" means
It is the temperature that only about 1% of winter hours fall below — not the record low. Engineers size equipment to it, and it is the number to compare a heat pump's low-temperature rating against. A unit rated to 14°F in this zone has no margin; one rated 10-15 degrees below it does.
States predominantly in this zone
Delaware, District of Columbia, Kansas, Kentucky, Maryland, Missouri, New Jersey, Tennessee, Virginia.
Large states span several zones — elevation and latitude shift this locally. Use your county's designation if you are near a boundary.
Heat pumps that work in zone 4A
Ranked by cold-weather capability against this zone's design temperature. Products rated above 14°F are shown with a warning rather than hidden.
Carrier Infinity 24 Heat Pump with Greenspeed Intelligence (25VNA4)
- Enough heat for an average house, roughly 1,400-2,000 sq ft Rated capacity: 36,000 BTU/h
- Still puts out full heat when it's 5°F outside, so your backup heater stays off Capacity retained at 5°F: 100%
- Its cold-weather performance has been independently measured and published, not just claimed in a brochure NEEP cold-climate listed: Yes
- Communicating - full features on the brand's own thermostat, but you're tied to that brand's dealer when a control board fails Thermostat compatibility: communicating
$8,900 – $10,100
equipment only · est. — install labour backed out of an observed installed price
Gree Sapphire Ultra SAP12HP230V1AO Single-Zone Ductless System
- Still puts out full heat when it's 5°F outside, so backup heat stays off Capacity retained at 5°F: 98%
- On a 5°F night it still delivers about twice the heat of a plain electric heater for the same electricity COP at 5°F: 2.11
- Scores 9 on the official heating efficiency test — closer to the legal minimum HSPF2: 9
$2,984 – $4,484
equipment only · est. — outdoor unit from 1 seller, indoor air handler added
Mitsubishi MSZ-FS09NA / MUZ-FS09NA Single-Zone Ductless System
- Keeps 89% of its heat when it's 5°F outside — backup heat only steps in occasionally Capacity retained at 5°F: 89%
- On a 5°F night it still delivers about twice the heat of a plain electric heater for the same electricity COP at 5°F: 2.21
- Scores 10 on the official heating efficiency test — solidly above the legal minimum HSPF2: 10
$2,143 – $2,143
equipment only · 1 seller · seen 2026-08-16
Mitsubishi P-series PUZ-AK48NLHZ Hyper-Heat Ducted System
- Enough heat for a mid-to-large house, roughly 2,000-2,800 sq ft Rated capacity: 48,000 BTU/h
- Keeps 87% of its heat when it's 5°F outside - backup heat only steps in occasionally Capacity retained at 5°F: 87%
- Its cold-weather performance has been independently measured and published, not just claimed in a brochure NEEP cold-climate listed: Yes
- Open 24V - works with any standard thermostat, and any competent tech can service it Thermostat compatibility: open
$7,428 – $8,928
equipment only · est. — outdoor unit from 1 seller, indoor air handler added
Mitsubishi M-Series SUZ-AK36NLHZ Hyper-Heating
- Enough heat for an average house, roughly 1,400-2,000 sq ft Rated capacity: 36,000 BTU/h
- Keeps 85% of its heat when it's 5°F outside - backup heat only steps in occasionally Capacity retained at 5°F: 85%
- Its cold-weather performance has been independently measured and published, not just claimed in a brochure NEEP cold-climate listed: Yes
- Open 24V - works with any standard thermostat, and any competent tech can service it Thermostat compatibility: open
$6,043 – $8,008
equipment only · est. — outdoor unit from 1 seller, indoor air handler added
Fujitsu Halcyon XLTH Extra Low Temperature Heating
- Keeps 80% of its heat when it's 5°F outside — backup heat only steps in occasionally Capacity retained at 5°F: 80%
- Its cold-weather performance has been independently measured and published, not just claimed in a brochure NEEP cold-climate listed: Yes
- On a 5°F night it delivers a modest efficiency edge over plain electric heat COP at 5°F: 2
- Scores 12 on the official heating efficiency test — solidly above the legal minimum HSPF2: 12
$3,669 – $5,169
equipment only · est. — outdoor unit from 1 seller, indoor air handler added
Bosch IDS Ultra Inverter Ducted Split
- Enough heat for an average house, roughly 1,400-2,000 sq ft Rated capacity: 36,000 BTU/h
- Drops to 78% of its heat at 5°F, so backup heat does part of the work on cold nights Capacity retained at 5°F: 78%
- Open 24V - works with any standard thermostat, and any competent tech can service it Thermostat compatibility: open
$6,616 – $10,685
equipment only · 2 sellers · seen 2026-08-16
Daikin Fit Aurora DH9VS
- Enough heat for an average house, roughly 1,400-2,000 sq ft Rated capacity: 36,000 BTU/h
- Drops to 75% of its heat at 5°F, so backup heat does part of the work on cold nights Capacity retained at 5°F: 75%
- Communicating - full features on the brand's own thermostat, but you're tied to that brand's dealer when a control board fails Thermostat compatibility: communicating
$5,500 – $8,000
equipment only · rough estimate, no seller data yet
LG LGRED° Single-Zone Ductless Heat Pump
- Drops to 72% of its heat at 5°F, so backup heat does part of the work on cold nights Capacity retained at 5°F: 72%
- On a 5°F night it delivers a modest efficiency edge over plain electric heat COP at 5°F: 1.9
- Scores 11 on the official heating efficiency test — solidly above the legal minimum HSPF2: 11
$2,440 – $2,440
equipment only · 1 seller · seen 2026-08-16
Daikin Aurora Multi-Zone Ductless System
- Drops to 70% of its heat at 5°F, so backup heat does part of the work on cold nights Capacity retained at 5°F: 70%
- On a 5°F night it delivers a modest efficiency edge over plain electric heat COP at 5°F: 1.85
- Scores 10.5 on the official heating efficiency test — solidly above the legal minimum HSPF2: 10.5
$7,005 – $9,077
equipment only · est. — outdoor unit from 1 seller, indoor air handler added
Mitsubishi FX Deluxe Single-Zone Hyper-Heating (MUZ-FX)
- Drops to 70% of its heat at 5°F, so backup heat does part of the work on cold nights Capacity retained at 5°F: 70%
- Its cold-weather performance has been independently measured and published, not just claimed in a brochure NEEP cold-climate listed: Yes
- On a 5°F night it still delivers about twice the heat of a plain electric heater for the same electricity COP at 5°F: 2.2
- Scores 13.3 on the official heating efficiency test — among the highest in this catalog HSPF2: 13.3
$3,990 – $3,990
equipment only · 1 seller · seen 2026-08-16
Trane 19 Multi-Speed Low Profile Cold Climate Heat Pump
- Enough heat for an average house, roughly 1,400-2,000 sq ft Rated capacity: 36,000 BTU/h
- Drops to 68% of its heat at 5°F, so backup heat does part of the work on cold nights Capacity retained at 5°F: 68%
- Open 24V - works with any standard thermostat, and any competent tech can service it Thermostat compatibility: open
$6,000 – $9,000
equipment only · rough estimate, no seller data yet
Fujitsu Airstage Ducted Single-Zone Heat Pump
- Enough heat for an average house, roughly 1,400-2,000 sq ft Rated capacity: 36,000 BTU/h
- Open 24V - works with any standard thermostat, and any competent tech can service it Thermostat compatibility: open
$5,404 – $6,904
equipment only · est. — outdoor unit from 1 seller, indoor air handler added
Lennox SL25XPV Variable-Capacity Heat Pump
- Enough heat for a mid-to-large house, roughly 2,000-2,800 sq ft Rated capacity: 48,000 BTU/h
- Its cold-weather performance has been independently measured and published, not just claimed in a brochure NEEP cold-climate listed: No
- Communicating - full features on the brand's own thermostat, but you're tied to that brand's dealer when a control board fails Thermostat compatibility: communicating
$23,496 – $23,496
equipment only · est. — install labour backed out of an observed installed price
Bosch Climate 5000 Single-Zone Ductless System
- Scores 9.5 on the official heating efficiency test — closer to the legal minimum HSPF2: 9.5
Price not yet sourced
we haven't found a defensible price
Carrier Performance 26 37MARA Single-Zone Ductless System
- Scores 13.6 on the official heating efficiency test — among the highest in this catalog HSPF2: 13.6
Price not yet sourced
we haven't found a defensible price
Samsung WindFree RXX12AMD / RNX12AMD Single-Zone Ductless System
- On a 5°F night the efficiency advantage over plain electric heat is largely gone COP at 5°F: 1.76
- Scores 9 on the official heating efficiency test — closer to the legal minimum HSPF2: 9
$1,749 – $1,749
equipment only · 1 seller · seen 2026-08-16
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