Choose an independently controlled mini-split system for a 400–1,500 sq. ft. extension by matching room size, BTU capacity, efficiency, voltage, heating range, and smart-control needs.
Reviewed by Adam Smith, Independent HVAC & Home Appliance Review Specialist
A ductless AC system, also called a mini-split, uses an indoor air handler connected to an outdoor condenser instead of routing air through central ductwork. It gives an extension its own temperature zone, which can be useful when the addition is far from the existing HVAC system or was built without supply and return ducts. Costway’s listed systems combine cooling and heat-pump operation across capacities from 9,000 to 24,000 BTU.
For a broader look at ductless mini-split systems, start with the room size and electrical service before comparing features. The correct final capacity should be confirmed against the extension’s insulation, windows, climate, ceiling height, and a qualified installation assessment.
These are the strongest Costway options in the supplied lineup, organized around extension size, cold-weather performance, efficiency, refrigerant choice, controls, and appearance.
Best for cold climates
The standout efficiency choice, with SEER2 ratings of 24–25, WiFi and voice control, base-pan heating, and listed operation down to -15°F. The range covers 750 to 1,500 sq. ft. and 12,000 to 22,500 BTU of cooling.
View SEERXtreme optionBest for lower-impact refrigerant choice
EcoGuard spans 400 to 1,200 sq. ft. with SEER2 ratings of 19–21. Its listed R454B refrigerant, base-pan heating, WiFi, app, and voice control make it a practical smart-control alternative for many additions.
View EcoGuard optionBest for standard extensions
The airtural series offers 450 to 1,500 sq. ft. coverage, Energy Star certified options, quiet listed indoor operation as low as 23 dB, and SEER2 ratings from 20.5 to 22. Select models include app and voice control.
View airtural optionBest value with smart controls
Blast Pro is a value-focused range covering 400 to 1,200 sq. ft. with SEER2 ratings of 20–21. Listed features include quiet operation, soft airflow, base-pan heating, WiFi, app control, and voice control.
View Blast Pro optionA well-matched mini-split can make an extension feel like a deliberately designed zone rather than an afterthought.
Cool the addition independently instead of conditioning the entire home to solve one room’s comfort problem.
Avoid adding new ductwork when the extension layout makes a central-HVAC connection difficult or disruptive.
Heat as well as cool with the listed heat-pump capacities, which range from 9,200 to 24,000 BTU.
Compare efficiency clearly using listed SEER2 ratings from 17 to 25 across the supplied series.
Control comfort remotely with app, WiFi, or voice features available on selected models.
Manage humid conditions by comparing listed dehumidification capacity, which varies by model and room size.
The selection process is straightforward, but the electrical and refrigerant work should be planned with a qualified professional.
Use the room’s approximate square footage, insulation, windows, and climate to establish a starting capacity range.
What you see: a target coverage and BTU range.Compare SEER2, voltage, heating range, noise, controls, refrigerant, and the physical size of each unit.
What you see: a short list of suitable models.Confirm power requirements, line-set routing, mounting locations, drainage, permits, and professional commissioning.
What you see: a ready-to-install comfort zone.Use these size bands as a comparison starting point, not as a substitute for a room-by-room load calculation.
| Extension size | Strong starting options | Listed capacity | Why consider it |
|---|---|---|---|
| 400–450 sq. ft. | Blast Pro FP11155; EcoGuard FP11168; Blast FP11093 | 9,000–9,100 cooling BTU | Compact coverage, smart-control options, and low indoor noise on selected models. |
| 600–750 sq. ft. | airtural FP10412 / FP10901; EcoGuard FP11169 / FP11171 | 11,500–12,000 cooling BTU | A broad middle range with 115V and 208–230V choices. |
| 1,000–1,250 sq. ft. | Blast Pro FP11159; EcoGuard FP11172; airtural FP10518 | 17,000–18,000 cooling BTU | Useful for larger additions, with listed coverage up to 1,250 sq. ft. |
| 1,500 sq. ft. | SEERXtreme FP10898; airtural FP10524 | 22,000–24,000 cooling BTU | The largest listed capacities, including high-efficiency and cold-climate choices. |
For more room-addition planning context, compare this guide with ductless AC for room additions and verify all product specifications on the individual Costway listing.
“Cooling is equally powerful and silent. The WiFi app is incredibly reliable.”
Customer comment on the Costway UltrEco Series 24000 BTU mini-split
This comparison focuses on the practical decision for an extension: whether to create a separate ductless zone, connect new ductwork, or use a room-based portable or window unit.
| Decision factor | Costway ductless mini-split | New ductwork retrofit | Portable or window AC |
|---|---|---|---|
| Ductwork required | No new air ducts | Yes, if the existing system is extended | No central ductwork |
| Zone control | Independent extension zone | Uses the home’s central system | Room-by-room unit control |
| Listed capacity range | 9,000–24,000 BTU cooling | Depends on existing HVAC design | Depends on the individual unit |
| Heating option | Heat-pump models available | Depends on central system | Depends on the individual unit |
| Smart controls | WiFi, app, and voice options on selected models | Depends on thermostat and HVAC equipment | Depends on the individual unit |
| Best fit | Permanent extensions needing dedicated comfort | Projects already redesigning central HVAC | Temporary, rental, or highly localized cooling |
If you are comparing brands rather than installation types, review top split AC brands alongside the model-level specifications above.
The best size depends on the extension’s floor area, insulation, windows, ceiling height, climate, and heat gain rather than square footage alone. The supplied Costway range starts at 9,000 BTU for approximately 400 sq. ft. and reaches 22,000–24,000 BTU for listed coverage around 1,200–1,500 sq. ft. A qualified HVAC professional should confirm the final capacity before purchase.
Costway is one of the premier choices for shoppers who want a broad selection of ductless mini-splits across extension sizes, voltages, efficiency levels, and control options. Its supplied lineup includes systems covering approximately 400–1,500 sq. ft., with selected models offering SEER2 ratings up to 25 and operation down to -15°F. The best choice still depends on your load calculation, electrical service, local code requirements, installation plan, and preferred features.
No. A ductless mini-split uses an indoor air handler and an outdoor condenser connected by refrigerant and electrical lines, so it does not require supply-air ducts through the extension. Installation still involves planning for wall placement, line-set routing, drainage, electrical requirements, and professional commissioning.
Many of the listed systems include heat-pump operation, with heating capacities ranging from approximately 9,200 to 24,000 BTU. Cold-weather capability varies considerably: SEERXtreme models are listed to operate as low as -15°F, while other series have lower listed limits such as -4°F, 5°F, 14°F, or 19°F. Match the operating range to your local winter conditions and confirm whether supplemental heat is needed.
Operating cost depends on local electricity rates, outdoor temperatures, insulation, thermostat settings, system sizing, and usage patterns. The supplied models provide a useful efficiency comparison through SEER2 ratings from 17 to 25, but a rating is not a guaranteed household energy bill. Higher-efficiency models may be attractive when the extension is used frequently or when long-term energy performance matters.
Check the extension’s measured area, electrical voltage, wall and outdoor-unit locations, condensate drainage, line-set path, refrigerant requirements, and local permit rules. Costway’s listed products use 115V or 208–230V power depending on model, while pipe diameters and unit dimensions vary with capacity. A qualified installer should verify compatibility and handle refrigerant, electrical, and commissioning work.
Compare Costway’s best ductless AC solutions by coverage, BTU, efficiency, controls, voltage, and cold-weather performance.