Central air costs $4,000–$12,000 installed and cools your entire home through ducts. Ductless mini splits cost $3,000–$8,000 for multi-zone setups and offer zone-by-zone control without ductwork. Window AC units cost $150–$700 per unit and require no installation — but they're loud, inefficient, and only cool one room at a time.
The right choice depends on your home's existing infrastructure, how many rooms you need to cool, your budget, and your comfort priorities. This comparison breaks down every factor with real numbers.
Quick Comparison Overview
| Factor | Central Air | Mini Split | Window AC |
|---|---|---|---|
| Whole-home cooling cost | $4,000–$12,000 | $5,000–$15,000 (4 zones) | $600–$2,800 (4 units) |
| Single-room cooling cost | N/A (whole-home) | $1,500–$4,000 | $150–$700 |
| SEER2 efficiency | 14.3–26 | 15–30+ | 9–12 (CEER) |
| Monthly operating cost | $80–$180 | $60–$150 | $30–$100 per unit |
| Installation complexity | High (requires ducts) | Moderate (no ducts) | None (DIY) |
| Noise (indoor) | 25–35 dB | 19–35 dB | 50–65 dB |
| Humidity control | Good–Excellent | Good–Excellent | Fair |
| Heating capability | No (AC only)* | Yes (heat pump) | Some models |
| Zone control | Limited (needs dampers) | Built-in (per unit) | Per unit |
| Home value impact | +5–10% | +2–5% | None/negative |
| Lifespan | 15–20 years | 15–20 years | 8–12 years |
| Aesthetic impact | Hidden (ducts in walls) | Wall-mounted indoor units | Blocks window |
*Central heat pumps provide heating and cooling. Standard AC-only systems require a separate furnace.
Cost Comparison: The Full Picture
Upfront Costs
| Scenario | Central Air | Mini Split | Window AC |
|---|---|---|---|
| Single room (12×15 ft) | Not applicable | $1,500–$4,000 | $200–$500 |
| 2-bedroom apartment | Not practical | $3,000–$6,000 (2 zones) | $400–$1,000 |
| 3-bedroom home (1,800 sq ft) | $5,000–$8,500 | $5,000–$10,000 (3–4 zones) | $800–$2,000 (4 units) |
| 4-bedroom home (2,500 sq ft) | $6,500–$11,000 | $8,000–$15,000 (4–5 zones) | $1,200–$3,000 (5–6 units) |
| Home with no existing ducts | $10,000–$18,000 | $5,000–$10,000 (3–4 zones) | $800–$2,000 |
Operating Costs (Annual)
Based on a 3-ton equivalent cooling load (1,800 sq ft home), 1,500 cooling hours/year, $0.14/kWh:
| System | Efficiency | Annual kWh | Annual Cost | 10-Year Cost |
|---|---|---|---|---|
| Window AC (4 units) | 10 CEER avg | 5,400 | $756 | $7,560 |
| Central AC (14.3 SEER2) | 14.3 SEER2 | 3,020 | $423 | $4,230 |
| Central AC (18 SEER2) | 18 SEER2 | 2,400 | $336 | $3,360 |
| Mini split (16 SEER2) | 16 SEER2 | 2,700 | $378 | $3,780 |
| Mini split (22 SEER2) | 22 SEER2 | 1,960 | $274 | $2,740 |
| Central AC (24 SEER2) | 24 SEER2 | 1,800 | $252 | $2,520 |
Total Cost of Ownership (10 Years)
| System | Upfront | 10-Year Energy | Maintenance | Total 10-Year Cost |
|---|---|---|---|---|
| Window AC (4 units, 1 replacement cycle) | $1,200 + $1,200 | $7,560 | $0 | $9,960 |
| Central AC (14.3 SEER2) | $5,200 | $4,230 | $1,500 | $10,930 |
| Central AC (18 SEER2) | $7,000 | $3,360 | $1,500 | $11,860 |
| Mini split (3-zone, 20 SEER2) | $7,500 | $2,900 | $1,200 | $11,600 |
| Central AC (24 SEER2) | $11,000 | $2,520 | $1,500 | $15,020 |
Window units look cheapest upfront but cost the most over 10 years when you factor in replacement cycles (they last 8–12 years vs. 15–20 for central or mini splits) and significantly higher energy bills. For a whole-home cooling need, central air or mini splits win on total cost of ownership.
Efficiency Deep Dive
How Efficiency Ratings Differ
These three system types use different efficiency rating systems, making direct comparison confusing:
| Rating | Used For | Scale | What It Measures |
|---|---|---|---|
| SEER2 | Central AC, mini splits | 14–30+ | Seasonal average efficiency with realistic duct pressure |
| EER2 | Central AC, mini splits | 10–18 | Efficiency at peak conditions (95°F outdoor) |
| CEER | Window AC | 8–15 | Combined efficiency including standby power |
To compare across systems, convert everything to approximate watts per BTU/hr removed:
| System Type | Efficiency | Watts per 12,000 BTU/hr |
|---|---|---|
| Window AC (10 CEER) | Low | 1,200 W |
| Central AC (14.3 SEER2) | Minimum | 840 W |
| Central AC (18 SEER2) | Mid | 667 W |
| Mini split (20 SEER2) | Mid-high | 600 W |
| Mini split (30 SEER2) | Ultra-high | 400 W |
Mini splits achieve higher efficiency because they avoid duct losses (which waste 20–30% in typical central systems) and nearly all models use inverter-driven compressors that modulate output to match the load.
Duct Loss Factor
Central AC loses 20–30% of its rated efficiency through duct losses in typical installations. This means a 16 SEER2 central AC effectively delivers about 11–13 SEER2 worth of cooling to your rooms if ducts run through an unconditioned attic.
Mini splits eliminate this loss entirely — the indoor unit delivers cooling directly to the room. This is why a 20 SEER2 mini split often outperforms a 24 SEER2 central system in practice.
Comfort and Performance
Temperature Control
| Factor | Central Air | Mini Split | Window AC |
|---|---|---|---|
| Temperature accuracy | ±1–2°F (single-stage), ±0.5°F (variable) | ±0.5–1°F (inverter) | ±3–5°F |
| Response time | 5–15 min | 3–10 min | 10–20 min |
| Distribution evenness | Good (with proper duct design) | Excellent in zone, limited beyond | One room only |
| Hot/cold spots | Possible (duct issues) | Minimal | Severe (far corners) |
Humidity Control
Humidity control matters as much as temperature for comfort, especially in the Southeast, Gulf Coast, and Mid-Atlantic states.
| System | Dehumidification Ability | Why |
|---|---|---|
| Central AC (single-stage) | Fair — 40–55% RH | Short cycles don't allow enough moisture removal |
| Central AC (variable-speed) | Excellent — 40–50% RH | Long, low-speed cycles maximize dehumidification |
| Mini split (inverter) | Good to excellent — 40–50% RH | Continuous low-speed operation removes moisture steadily |
| Window AC | Poor to fair — 50–65% RH | Limited coil area, inconsistent cycling |
Noise Levels
| System | Indoor Noise | Outdoor Noise | Notes |
|---|---|---|---|
| Central AC | 25–35 dB (air through registers) | 65–76 dB (condenser) | Indoor noise is mainly airflow; outdoor can be loud |
| Mini split | 19–35 dB (wall unit) | 48–60 dB (outdoor unit) | Quietest overall, especially premium brands |
| Window AC | 50–65 dB (unit itself) | Same unit (faces outside) | Loudest by far, equivalent to normal conversation |
For reference: 20 dB = rustling leaves, 30 dB = whisper, 50 dB = moderate rainfall, 60 dB = normal conversation, 70 dB = vacuum cleaner.
Installation Comparison
| Factor | Central Air | Mini Split | Window AC |
|---|---|---|---|
| Professional required | Yes | Yes | No |
| Installation time | 4–8 hours (replacement), 2–4 days (new) | 4–8 hours per zone | 15–30 minutes per unit |
| Home modification | Ductwork in walls/attic | 3-inch hole per wall unit | None (window mount) |
| Permits required | Yes (most areas) | Usually yes | No |
| Electrical requirements | Dedicated 30–60A circuit | Dedicated 15–30A circuit per zone | Standard 120V outlet (most) |
| Can you move it? | No | No | Yes |
When Each System Makes Sense for Installation
Central air is best when:
- You already have ductwork from an existing furnace
- You want whole-home cooling from a single system
- You plan to stay in the home long-term (5+ years)
- Home resale value matters to you
Mini splits are best when:
- You have no existing ductwork (saves $4,000–$8,000 vs. installing ducts)
- You want room-by-room temperature control
- You need both heating and cooling from one system
- You're cooling an addition, garage, or room where duct extension is impractical
Window AC is best when:
- You're renting and can't modify the building
- You need to cool 1–2 rooms only
- Your budget is under $500
- You need cooling temporarily (seasonal home, while saving for a permanent system)
Real-World Scenarios
Scenario 1 — 1,600 sq ft ranch with existing ducts (Ohio): The Petersons have a 20-year-old furnace with ductwork. Central air replacement won: $5,800 installed (3-ton, 16 SEER2). Mini split equivalent would cost $7,500 for 3 zones. The existing duct infrastructure made central air $1,700 cheaper with better whole-home coverage.
Scenario 2 — 1920s bungalow with no ducts (Portland, OR): The Chens had baseboard heat and no ductwork. Mini split won: $6,800 for a 3-zone Mitsubishi system that provides both heating and cooling. Central air would have cost $14,000+ with new ductwork, and the old house had limited space for duct runs. The mini split also eliminated their electric baseboard heating, saving $600/year.
Scenario 3 — College apartment (any city): Marcus rents a 600 sq ft apartment and can't install permanent equipment. Window AC won: $350 for a 10,000 BTU unit that cools his entire apartment adequately. He'll take it with him when he moves. A portable AC at $400–$600 was the alternative, but window units are 20–30% more efficient.
Scenario 4 — 3,200 sq ft two-story (Dallas, TX): The Garcias wanted room-by-room control for a home with frequent hot spots upstairs. Hybrid approach won: They kept their existing 4-ton central air for the main floor and added a 2-zone mini split for the upstairs bedrooms ($4,200). Total cost: $4,200 (mini splits only, since central system was only 8 years old). This solved the temperature imbalance without replacing the entire system.
Aesthetic and Property Value Impact
| Factor | Central Air | Mini Split | Window AC |
|---|---|---|---|
| Indoor visibility | Registers only (flush with floor/wall) | Wall-mounted cassettes (7×30 inches each) | Large box in window |
| Curb appeal | Outdoor unit beside house | Smaller outdoor units | Visible from outside |
| Blocks natural light | No | No | Yes (partially blocks window) |
| Security risk | No | No | Yes (window must remain partially open on some models) |
| Home value impact | +$2,500–$10,000 (5–10% in hot markets) | +$1,000–$5,000 (growing in value) | $0 or negative |
Resale note: Central air is expected in most U.S. markets. Homes without central air sell for 5–10% less than comparable homes with it. Mini splits are increasingly accepted but some buyers still perceive them as "less than" central air, particularly in suburban markets. Window AC units should be removed before listing — they signal to buyers that the home lacks proper cooling.
Maintenance Comparison
| Maintenance Task | Central Air | Mini Split | Window AC |
|---|---|---|---|
| Filter changes | Every 1–3 months ($5–$30) | Every 2–4 weeks (washable, $0) | Every 2–4 weeks (washable, $0) |
| Professional tune-up | $100–$200/year | $100–$200/year per system | Not typical |
| Coil cleaning | Annual (professional) | Every 6–12 months (DIY possible) | Seasonal (DIY) |
| Drain line cleaning | Seasonally | Seasonally (per unit) | Empty drip tray as needed |
| Refrigerant check | Annual (professional) | Annual (professional) | Not serviceable |
| Expected repair costs (annual avg) | $150–$300 | $100–$250 | Replace unit if fails |
| Deep cleaning (mini split specific) | N/A | $150–$300/unit every 2–3 years | N/A |
Mini split indoor units require more frequent cleaning than central AC. The blower wheel and evaporator coil inside wall-mounted units collect dust, mold, and biological growth over time. If you notice musty odors, the unit needs a deep clean. Budget for professional deep cleaning ($150–$300 per indoor unit) every 2–3 years.
Hybrid Approaches
You don't have to choose just one. Common hybrid setups include:
Central air + mini split supplement: Use central air for the main living areas and add 1–2 mini split heads in problem areas (bonus rooms, sunrooms, home offices, garages). Cost: $1,500–$4,000 for the mini split addition.
Mini split primary + window AC backup: Use a multi-zone mini split for main rooms and a window unit for a rarely-used guest room. Saves $1,500–$3,000 vs. adding another mini split zone.
Central air + window AC for garage/workshop: If your garage isn't connected to your duct system, a 10,000–12,000 BTU window unit ($300–$500) is much cheaper than extending ductwork.
Key Takeaways:
- Choose central air if you have existing ductwork and want whole-home cooling — it's the most cost-effective for homes already set up for it
- Choose mini splits if you have no ducts, want zone control, or need heating + cooling — they're more efficient and avoid duct losses
- Choose window AC only for temporary cooling, rentals, or single-room needs on a tight budget
- Mini splits are 20–40% more efficient than central AC in practice due to zero duct losses
- Central air adds 5–10% to home value; mini splits add 2–5%; window units add nothing
- For homes without ducts, mini splits save $4,000–$8,000 vs. installing ductwork for central air
- Hybrid approaches (central + mini split supplement) solve hot-spot problems for $1,500–$4,000