Most homeowners think of through-the-wall air conditioners as summertime allies—machines designed to battle sweltering July afternoons while preserving precious window space. But modern technology has blurred the lines between cooling and heating equipment. Many through-the-wall ACs now come equipped with built-in heating functions, making them potential year-round climate control solutions.
This isn’t just a convenience—it’s a space saver, a money saver, and for some homes without ductwork, a lifeline. The key is understanding how these units produce heat, how effective they are, and whether they can truly replace—or just supplement—other heating systems.
In this guide, you’ll learn:
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Which types of through-the-wall ACs can produce heat
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The two main heating technologies (electric resistance vs. heat pump)
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Performance differences in mild vs. harsh winters
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Cost breakdowns for heating with each method
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How to choose the right unit for your climate and budget
By the end, you’ll know if a dual-function through-the-wall AC can be your primary heating solution or just a seasonal backup.
2. Do All Through-the-Wall AC Units Provide Heat?
Short answer: No.
There are three main categories of through-the-wall units:
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Cooling-only models — strictly for summer use.
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Cooling + electric resistance heat — uses built-in heating elements.
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Cooling + reverse-cycle heat pump — uses refrigerant to extract heat from outside air.
If your unit is cooling-only, there’s no “switch” or “add-on” to make it produce heat—you’d have to replace it with a heating-capable model.
💡 Savvy Tip: When shopping, look for terms like “with heater,” “heat pump,” “reverse cycle,” or “cooling & heating” in the product title. If those words aren’t there, it’s almost certainly cooling-only.
3. How Through-the-Wall Units Provide Heat
A. Electric Resistance Heating
How it works:
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Similar to a space heater built into the AC.
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Electric current passes through heating coils, generating warmth.
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The built-in fan circulates warm air into the room.
Advantages:
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Works in any temperature—performance isn’t affected by outdoor conditions.
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Lower initial purchase price than heat pump units.
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Simple technology—less that can break down.
Drawbacks:
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Efficiency is always 1:1—every 1 kWh of electricity produces 1 kWh of heat.
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Higher operating cost for frequent use.
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Generates dry heat, which can reduce indoor humidity.
B. Heat Pump Heating
How it works:
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The AC’s refrigeration cycle is reversed.
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The outdoor coil absorbs heat from outside air, even in cool conditions.
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That heat is transferred indoors and blown into the room.
Advantages:
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More efficient—2–4 times more heat per kWh than resistance heaters in mild weather.
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Lower monthly operating costs.
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Provides gentler, more even warmth.
Drawbacks:
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Loses efficiency as outdoor temps drop, especially below 25–30°F.
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Higher upfront cost.
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May need backup heat in colder climates.
4. Heating Effectiveness by Climate
Mild Winter (above 35°F most days)
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Heat pumps shine—can cover most or all heating needs.
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Resistance heat works fine, but costs more to operate.
Moderate Winter (frequent 25–35°F days)
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Heat pumps still useful, but may need supplemental heat for cold snaps.
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Resistance heat works consistently, but expect higher bills.
Harsh Winter (below 20°F often)
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Heat pumps lose significant efficiency.
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Resistance heat or central heating is more reliable for primary warmth.
5. Pros & Cons of Heating with a Through-the-Wall Unit
| Pros | Cons |
|---|---|
| One appliance for year-round comfort | Heating capacity limited to a single room |
| Saves space vs. separate AC & heater | May require separate electrical circuit |
| No ductwork needed | Heat pumps underperform in very cold temps |
| Quick mode switching between heating & cooling | Electric resistance heating has high operating costs |
| Can be installed in rooms without central heat | Noise level may be higher than central systems |
6. Costs: Purchase & Operation
Upfront Costs
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Cooling-only unit: $450–$750
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Cooling + electric heat: $550–$900
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Cooling + heat pump: $650–$1,200
Operating Costs Example (12,000 BTU / ~3,500 W heat output)
Electric Resistance Heat:
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Draw: ~3,500 watts (3.5 kW)
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Usage: 6 hrs/day × 30 days = 180 hours/month
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Electricity cost @ $0.15/kWh =
3.5 kW × 180 hrs × $0.15 = $94.50/month
Heat Pump (COP 3.0, ~1,170 W draw):
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Usage: same as above
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Electricity cost @ $0.15/kWh =
1.17 kW × 180 hrs × $0.15 = $31.59/month
💡 Savvy Insight: In mild climates, a heat pump could cut your heating cost by two-thirds compared to electric resistance.
7. Other Factors That Affect Heating Performance
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Room Insulation — Poorly insulated rooms lose heat quickly, making any system work harder.
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Unit Sizing — Undersized units won’t keep up; oversized units waste energy.
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Placement — Install on an exterior wall with minimal exposure to strong winds.
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Maintenance — Clean filters and coils for optimal airflow and heat transfer.
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Electrical Circuit — Many heating models require a dedicated 220V circuit.
8. Choosing the Right Heating Option
If your winters are mild:
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A heat pump through-the-wall unit is the most efficient and cost-effective choice.
If your winters are cold:
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An electric resistance heating model ensures reliable performance regardless of outdoor temperature.
If you only need occasional heat:
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Either type works—choose based on budget and whether efficiency is a priority.
9. Savvy’s Shopping Checklist for Heating Models
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Decide on heating type — heat pump for efficiency, resistance for reliability.
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Check BTU rating for heating, not just cooling.
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Confirm voltage requirements—many heating models need 220V.
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Look for Energy Star certification—especially for heat pumps.
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Read reviews—focus on winter performance feedback.
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Compare warranties—some heating components have shorter coverage.
10. Installation Considerations for Heating Models
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Wall Sleeve — Must be insulated and sealed to prevent heat loss.
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Drainage — Heat pumps still produce condensate in winter.
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Electrical Safety — Heating elements draw more current—ensure wiring meets local code.
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Weather Protection — Keep the exterior clear of snow and ice.
11. Real-World Examples
Case 1: Mild Climate (Atlanta, GA)
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Home office, 250 sq. ft.
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9,000 BTU heat pump model covers entire winter needs.
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Electric bill for heating: ~$25/month.
Case 2: Moderate Climate (St. Louis, MO)
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400 sq. ft. den
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12,000 BTU heat pump handles most days; space heater used 10% of the time in January–February.
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Combined cost: ~$40–$50/month.
Case 3: Harsh Climate (Minneapolis, MN)
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350 sq. ft. upstairs bedroom
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Electric resistance heating used for supplemental warmth.
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Cost: ~$90/month during peak winter months.
12. Final Takeaways
Through-the-wall AC units can provide heat in the winter—if you choose a model built for it.
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Heat pumps are the best for energy savings and year-round use in mild-to-moderate climates.
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Electric resistance heating works anywhere but costs more to run long-term.
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Correct sizing, installation, and insulation are essential to get the most from your unit.
For many homeowners, a dual-function unit is the perfect solution for a sunroom, home office, guest room, or addition—anywhere central HVAC doesn’t reach efficiently.
In the Next topic we will read more about: How to Maintain Your Through-the-Wall AC: Filters, Coils & Seasonal Care
