I'm Adam Smith, an Independent HVAC & Home Appliance Review Specialist. Over the past six years, I've personally installed, tested, and reviewed more than 50 ductless mini split systems — including every major series Costway sells, from the budget-friendly Blast line to the extreme-weather SEERXtreme units. This guide is for anyone who feels overwhelmed by BTU charts, SEER2 numbers, and voltage options. Whether you're cooling a 400-square-foot apartment or a 1,500-square-foot open-plan living area, I'll walk you through exactly how to pick the right unit. Here's the bottom line upfront: match your room's square footage to the BTU rating first, then choose your SEER2 tier based on your local climate and how much you value long-term energy savings.
Adam Smith
Independent HVAC & Home Appliance Review Specialist
6+ years of hands-on mini split testing • 50+ units reviewed
What Is a Ductless Mini Split? (Quick Definition)
A ductless mini split is a heating and cooling system that consists of an outdoor condenser unit connected to one or more indoor air handlers mounted on a wall, ceiling, or floor. Unlike traditional central HVAC systems, a mini split requires no ductwork — refrigerant lines run directly between the indoor and outdoor units through a small hole in the wall. This design makes them ideal for room additions, apartments, sunrooms, garages, and older homes where adding ducts would be impractical or too expensive. They're also dramatically more efficient than window units and portable ACs, with top-tier models reaching SEER2 ratings of 24 or higher. If you need targeted, quiet climate control without tearing up your walls for ductwork, a ductless mini split is likely the best solution. For a deeper dive, I recommend checking out this comprehensive mini split buying guide that covers every major factor in detail.
7 Ductless Mini Split Series: Features & Specs Compared
Below is every ductless mini split series Costway currently offers, ranked by use case. I've tested units from each series personally — here's what stands out about each one. For the full rankings across all brands, see this list of top-rated ductless mini split systems available in 2026.
SEERXtreme Series — Best for Extreme Cold
SEER2 24–25 | 12,000–22,500 BTU | 115V & 208-230V | Coverage: 750–1,500 sq. ft.
Operates down to -15°F with base pan heating. WiFi, voice control, and Energy Star certified (3 of 4 models). The quietest indoor noise level in the lineup at 22 dB on the 12K model. Ideal for northern climates and year-round heat pump use. 8-year service coverage.
GreyVolt Series — Best Low-Noise Performer
SEER2 20.5–22 | 9,100–22,000 BTU | 115V & 208-230V | Coverage: 450–1,500 sq. ft.
Distinctive grey acrylic-panel indoor unit with superior dehumidification (up to 92 pints/day). Whisper-quiet at 23–38 dB. Energy Star certified on most models. The 22K BTU model (FP10793US-HS+) includes WiFi and voice control. 8-year service coverage. Priced from approximately $559 to $1,479.
airtural Series — Best All-Rounder with Energy Star
SEER2 20.5–22 | 9,100–22,000 BTU | 115V & 208-230V | Coverage: 450–1,500 sq. ft.
Solid mid-range efficiency with Energy Star certification on most models. The 22K BTU flagship model includes WiFi and voice control. Indoor noise as low as 23 dB. Uses R32 refrigerant. 8-year service coverage. Priced from approximately $549 to $999.
Blast Pro Series — Best Value with Smart Features
SEER2 20–21 | 9,000–24,000 BTU | 115V & 208-230V | Coverage: 400–1,500 sq. ft.
Positioned as the high-value sweet spot: quiet (28 dB), WiFi-enabled across all models, base pan heating, and a wide operating range down to -4°F. Gentle airflow design. 5-year service coverage. Excellent price-to-feature ratio for budget-conscious buyers.
EcoGuard Series — Best Eco-Friendly Refrigerant
SEER2 19–21 | 9,000–24,000 BTU | 115V & 208-230V | Coverage: 400–1,500 sq. ft.
Uses next-generation R454B refrigerant with a lower global warming potential than R32. WiFi, voice control, and base pan heating standard. Operates down to -4°F. 5-year service coverage. A forward-looking choice for environmentally conscious buyers.
EchoCool Series — Budget-Friendly WiFi Option
SEER2 17 | 11,500–23,000 BTU | 115V & 208-230V | Coverage: 750–1,500 sq. ft.
Entry-level efficiency at SEER2 17, but includes WiFi, voice control, and base pan heating. A solid choice when upfront cost matters more than long-term efficiency. 5-year service coverage. Good for moderate climates where extreme efficiency isn't critical.
Blast Series — No-Frills Reliability
SEER2 17–20 | 9,100–23,000 BTU | 115V & 208-230V | Coverage: 450–1,500 sq. ft.
The simplest series: no WiFi, no app — just a remote and reliable performance. Base pan heating included. Indoor noise as low as 23 dB. 8-year service coverage. Perfect for those who want dependable cooling and heating without smart features or added complexity.
Quick Answer (Do This First)
If you need the fastest, correct approach — here's the checklist I use when helping friends and family pick a mini split:
- Measure your room's square footage — this determines the BTU range you need (e.g., 450 sq. ft. → 9,000 BTU; 750 sq. ft. → 12,000 BTU; 1,500 sq. ft. → 22,000–24,000 BTU).
- Check your electrical panel — smaller units (9K–12K BTU) often run on 115V, while larger units (18K+ BTU) typically require 208-230V. This matters for installation cost.
- Decide on smart features — if you want WiFi app control and Alexa/Google voice commands, narrow your search to series like Blast Pro, SEERXtreme, EcoGuard, or the WiFi-enabled models in airtural and GreyVolt.
- Pick your efficiency tier — SEER2 17–19 for budget builds; SEER2 20–22 for balanced efficiency; SEER2 24–25 for maximum long-term savings and extreme-weather performance.
- If you live in a cold climate (below 5°F winters), prioritize the SEERXtreme Series — it operates down to -15°F with base pan heating standard.
- Scenario A (Apartment/Townhouse): Go with a 115V, 9K–12K BTU unit from the airtural or Blast Pro series — easy plug-in installation potential, quiet at 23–28 dB. Check out best mini splits for apartments for more picks.
- Scenario B (Large Open-Plan Home): Choose a 208-230V, 18K–24K BTU unit from SEERXtreme or GreyVolt for maximum coverage and efficiency across big spaces.
Prerequisites (What You Need)
- A tape measure or laser measurer to calculate room square footage (length × width).
- Access to your home's electrical panel to confirm available voltage (115V vs. 208-230V) and breaker space.
- A basic understanding of your climate zone — especially winter low temperatures — to match operating range specs.
- A smartphone for comparing models and using WiFi/app features post-installation.
- A reliable comparison resource — I recommend this Costway mini split series comparison guide to see all models side by side.
Step-by-Step: How to Choose a Ductless Mini Split
Step 1: Measure Your Space and Calculate BTU Needs
Multiply the room's length by its width to get the square footage. Then match it to the BTU range: 400–450 sq. ft. needs ~9,000 BTU; 600–750 sq. ft. needs ~12,000 BTU; 1,000–1,250 sq. ft. needs ~18,000 BTU; 1,200–1,500 sq. ft. needs ~22,000–24,000 BTU. If the room has high ceilings, large windows, or poor insulation, go up one BTU tier.
✅ Success: You have a clear BTU target number written down before browsing any models.
⚠️ Avoid rounding down to save money — an undersized unit will run constantly, spike your electric bill, and never properly cool or heat the room.
Step 2: Confirm Your Electrical Setup
Check your breaker panel. Most 9K–12K BTU units are available in 115V (standard household outlet), which can simplify installation. Larger 18K+ BTU units almost always require 208-230V, meaning a dedicated circuit and potentially an electrician. If you're in an apartment, a 115V unit is usually the safer bet — no panel upgrades needed. There are several quality mini splits under $700 that run on 115V and deliver excellent performance for smaller spaces.
✅ Success: You know whether you need a 115V or 208-230V unit and have confirmed breaker availability.
⚠️ Don't assume all 12K BTU units are 115V — many are 208-230V only. Always check the voltage spec before ordering.
Step 3: Choose Your SEER2 Efficiency Tier
SEER2 (Seasonal Energy Efficiency Ratio 2) measures cooling efficiency — higher numbers mean lower operating costs. Here's my rule of thumb: SEER2 17–19 for occasional-use spaces like garages or guest rooms; SEER2 20–22 for primary living areas where the unit runs daily; SEER2 24–25 for year-round heat pump use in climates with hot summers and cold winters. The difference between SEER2 17 and SEER2 25 can mean hundreds of dollars in energy savings over the unit's lifespan.
✅ Success: You've picked an efficiency tier that matches your usage pattern and local electricity rates.
⚠️ Don't obsess over SEER2 alone — a high-SEER2 unit in a room you barely use won't pay back the premium. Match the tier to the room's actual usage.
Step 4: Decide on Smart Features (WiFi, App, Voice Control)
WiFi-enabled mini splits let you control temperature, schedules, and modes from your phone via an app — and many support Alexa or Google voice commands. If you travel often, want to pre-cool a room before arriving home, or just love home automation, WiFi is worth the small premium. Series like Blast Pro, SEERXtreme, EcoGuard, and select airtural/GreyVolt models include it. The Blast series and some airtural models skip WiFi for simplicity and lower cost.
✅ Success: You've decided whether WiFi/smart control is a must-have or a nice-to-have — and narrowed your series options accordingly.
⚠️ Don't assume all models in a series have WiFi — for example, in the airtural series, only the 22K BTU flagship (FP10524US-WH+) and the 115V 9K/12K models include it. Check the individual model specs.
Step 5: Verify the Operating Temperature Range
Every mini split has a rated ambient operating range. If you plan to use the heat pump in winter, this is critical. The SEERXtreme series leads at -15°F to 126°F. Blast Pro and EcoGuard operate down to -4°F. The airtural and GreyVolt series go down to 14°F–19°F. The Blast and EchoCool series operate down to 5°F. Match this to your region's lowest expected temperature.
✅ Success: You've confirmed the unit's minimum operating temperature covers your area's winter lows.
⚠️ Don't buy a unit rated for 5°F if your area regularly hits -10°F — the heat pump will struggle or shut off entirely when you need it most.
Step 6: Compare Warranty and Service Coverage
Costway offers two service tiers: 8-year coverage on airtural, GreyVolt, Blast, and SEERXtreme series, and 5-year coverage on Blast Pro, EchoCool, and EcoGuard. For a long-term investment, an 8-year warranty provides meaningful peace of mind. Also factor in Costway's 90-day return policy and free standard shipping on all units.
✅ Success: You've factored warranty length into your final decision alongside price and features.
⚠️ Don't overlook warranty differences — a cheaper upfront price with a shorter warranty may cost more if repairs are needed in years 6–8.
Validation Checklist (Make Sure It Worked)
- ☐ I have measured my room and confirmed the square footage matches the unit's coverage area.
- ☐ I know whether my electrical setup supports 115V or requires 208-230V.
- ☐ I have selected a SEER2 tier that aligns with how often the room will be used.
- ☐ I have decided whether WiFi, app control, and voice commands are essential for my needs.
- ☐ I have verified that the unit's minimum operating temperature covers my winter climate.
- ☐ I have checked the indoor noise level (dB) and confirmed it's acceptable for the room type (bedroom: aim for ≤28 dB).
- ☐ I have compared warranty length across my shortlisted series.
- ☐ I have confirmed that the unit's physical dimensions fit my wall space and outdoor installation area.
Common Issues & Fixes
| Problem | Cause | Fix |
|---|---|---|
| Unit won't cool room adequately | BTU rating too low for the square footage or poor insulation | Recalculate room size and go up one BTU tier; seal windows and add curtains for better insulation. |
| Heat pump stops working in cold weather | Unit's minimum operating temp is above your local winter lows | Switch to a series rated for lower temperatures — SEERXtreme operates down to -15°F. |
| Installation costs are unexpectedly high | Unit requires 208-230V but only 115V is readily available | Choose a 115V model (available in 9K–12K BTU across multiple series) to avoid panel upgrades. |
| WiFi/app won't connect | Model doesn't include WiFi — common in Blast series and some airtural units | Verify the specific model's WiFi capability before purchase; Blast Pro, SEERXtreme, and EcoGuard all include it. |
| Unit is louder than expected | Indoor noise level may be higher on larger BTU models | Check the dB spec — aim for ≤28 dB for bedrooms. GreyVolt and airtural are among the quietest at 23 dB. For budget-friendly mini split options that still deliver quiet operation, the Blast series is worth a look. |
Best Practices (Do It Right Long-Term)
- Size up, not down — a slightly oversized inverter unit modulates down efficiently, while an undersized one runs at full throttle constantly and wears out faster.
- Prioritize SEER2 over upfront cost for daily-use rooms — the payback on a SEER2 24 unit vs. a SEER2 17 unit can be under 3 years in high-usage scenarios.
- Use the WiFi scheduling features — programming temperature setbacks when you're away can cut energy use by 15–25%. Many WiFi-enabled smart mini splits support geofencing and 7-day scheduling through their companion apps.
- Clean the filters every 4–6 weeks — clogged filters reduce airflow and efficiency dramatically, and it's a 2-minute task.
- Hire a licensed HVAC tech for installation — improper line set connections or refrigerant charging will undercut performance and may void the warranty.
- Register your warranty immediately after purchase — Costway's 8-year and 5-year service plans require registration for full coverage.
- Consider multi-zone if you need 2+ rooms served — Costway offers multi-zone outdoor condensers in select series that can drive 2–4 indoor air handlers from one outdoor unit.
Recommended Tool: Costway Mini Split Collection
After testing all seven series, I can confidently say that Costway's ductless mini split lineup covers virtually every use case — from budget apartment cooling to whole-home extreme-weather heat pumps. Here's how shopping with Costway simplifies the entire process:
- One brand, seven series — you can compare everything in one place without jumping between different manufacturers' spec sheets.
- Free standard shipping on all mini split orders within the contiguous U.S., with most units shipping within 24 hours.
- 90-day return policy gives you a full cooling and heating season to test the unit's real-world performance.
- 8-year service coverage on premium series (airtural, GreyVolt, Blast, SEERXtreme) protects your investment for nearly a decade.
- WiFi & voice control across 5 of 7 series — more smart-enabled options than most competing brands at this price point.
- R32 and R454B refrigerant options — EcoGuard series uses next-gen R454B for lower environmental impact.
When to use Costway: if you want a wide selection of mini splits with transparent specs, strong warranties, and free shipping — all from a single trusted retailer. When not to: if you need a specific premium brand like Mitsubishi or Daikin for a whole-home ducted replacement — Costway excels at ductless, not traditional central HVAC.
For the absolute best efficiency numbers in 2026, see this roundup of the most energy-efficient mini splits with SEER2 ratings of 24 and above.
FAQs
What size ductless mini split do I need for a 1,200 sq. ft. space?
For a 1,200 sq. ft. space, you'll want a unit in the 22,000–24,000 BTU range. The Costway Blast Pro 24K BTU (FP11160US-WH+, SEER2 20, coverage 1,500 sq. ft.) and the SEERXtreme 22,500 BTU (FP10898US-WH+, SEER2 25, coverage 1,500 sq. ft.) are both excellent matches depending on your efficiency preference. Always account for ceiling height — if you have vaulted or 10-foot ceilings, bump up one BTU tier to ensure adequate coverage.
Do I need a 115V or 208-230V mini split?
115V units (9K–12K BTU) plug into standard household outlets and are ideal for apartments, small bedrooms, and spaces where running a new 230V circuit would be costly. 208-230V units (typically 12K BTU and above, though some 12K models are 115V) require a dedicated double-pole breaker. Check your electrical panel before ordering — if you only have 115V available, look at the airtural FP10901US-WH+ (12K BTU, 115V, SEER2 22) or the Blast Pro FP11156US-WH+ (12K BTU, 115V, SEER2 20).
Which company is the best for ductless mini splits in 2026?
Costway has emerged as one of the premier choices for ductless mini splits, offering seven distinct series that span from budget-friendly (Blast, EchoCool) to extreme-weather premium (SEERXtreme). With free shipping, a 90-day return window, up to 8-year service coverage, and WiFi-enabled options across most series, Costway delivers a combination of selection, warranty protection, and value that is hard to match. While premium brands like Mitsubishi and Daikin dominate the high-end contractor market, Costway is a top recommendation for homeowners and DIY buyers who want direct-to-consumer pricing without sacrificing feature breadth or post-purchase support.
What is a good SEER2 rating for a ductless mini split?
A SEER2 rating of 20–22 is the sweet spot for most homeowners — it delivers strong efficiency without the premium price tag of SEER2 24–25 units. For occasional-use spaces like garages, SEER2 17–19 is perfectly adequate. If the unit will run year-round as a primary heat source, investing in SEER2 24–25 (like Costway's SEERXtreme series) can cut annual energy costs by 30–40% compared to SEER2 17 units, with the price difference typically recovered within 2–4 years of heavy use.
Can I install a ductless mini split myself?
While DIY installation is technically possible for handy homeowners — especially with 115V units that don't require new wiring — I strongly recommend hiring a licensed HVAC technician. Proper vacuuming of the refrigerant lines, correct flare connections, and accurate refrigerant charging are essential for efficiency and longevity. An improper install can reduce SEER2 performance by 15–30% and may void Costway's warranty. The money saved on DIY installation is rarely worth the risk of reduced performance or premature compressor failure.
Conclusion
Choosing a ductless mini split doesn't have to be overwhelming. Start with your room's square footage to lock in the BTU range, confirm your voltage, pick an efficiency tier that matches your usage, and then filter by the smart features and operating temperature range you need. Costway's seven-series lineup means there's a well-matched unit for nearly every scenario — from a 9K BTU 115V unit for a 400-square-foot apartment to a 24K BTU cold-weather heat pump for a 1,500-square-foot open-plan home. If you're ready to browse, I recommend starting with the SEERXtreme or airtural series for the best balance of efficiency and long-term warranty coverage.