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Verdict: Costway’s SEERXtreme 18,000 BTU mini-split has promising listed efficiency and a low-temperature operating claim, but the available specifications do not establish how much heat it delivers in severe cold, whether it fits a particular home, or what installation will cost. Treat it as a candidate to investigate—not a confirmed fit—until an installer checks the exact equipment combination, performance data, electrical requirements, and site.
What is the Costway SEERXtreme 18,000 BTU?
Costway lists a ductless, inverter-driven heat-pump system rated for 18,000 BTU of cooling and 18,200 BTU of heating. The listed configuration is 208–230V, 60Hz and uses R32 refrigerant. Costway’s pages describe Wi-Fi control and operation down to −13°F. These are manufacturer-listed claims; no independent test results were available to confirm performance. (Costway product listing; Costway product page)
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The product page identifies 25 SEER2 and 10.5 HSPF2. These ratings can help compare equipment, but they are not a prediction of a household’s energy bills. For a meaningful comparison, use the ratings for the exact indoor/outdoor equipment combination and consider local climate, installation quality, and how the system will be operated.
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How much space can it serve?
Costway gives a coverage estimate of 1,250 square feet. That is not a load calculation or a guarantee that the unit will heat or cool a space of that size. Required capacity depends on factors such as insulation, windows, ceiling height, air leakage, climate, layout, and whether rooms connect freely. Ask an HVAC professional to calculate the load for the actual space rather than sizing from the listing’s square-foot figure alone.
#1 Best Overall
- Powerful 18,000 Btu Cooling & Heating: Rellytech mini split heat pump system delivers 18,000 BTU cooling and 18,400 BTU heating, covering up to 1,250 sq. ft. Ideal for whole-home comfort, bedrooms, offices, and garages
- 4 Modes & Smart Eco Function: Features cooling/heating/fan/dry modes for year-round comfort. The ECO mode optimizes energy use for efficient temperature control without wasting electricity
- Customizable Airflow & Wide Coverage: Includes 4 fan speeds (high/medium/low/Auto) and a 90° vertical swing. Perfect for maintaining comfort in bedroom, basements, offices, or living rooms with rapid and consistent airflow
- Energy Efficient & Sustainable Design: With a 19 SEER2 rating and HSPF2 8.5, this pre-charged split-system air conditioner reduces energy costs while maintaining strong performance, offering a long-term cooling and heating solution for your home
Listed dimensions are 45 × 9 × 13 inches for the indoor unit and 35.5 × 14 × 27.5 inches for the outdoor unit. Costway also lists 765 CFM airflow, indoor noise of 28–50 dB, outdoor noise of 57 dB, and a setpoint range of 60–90°F. These are manufacturer specifications, not independently measured results.
Can it heat in very cold weather?
Costway states that the system can operate at outdoor temperatures as low as −13°F. That figure describes a stated operating boundary; it does not tell you how much heating capacity remains at that temperature or how efficiently the unit operates there. If the system must carry the heating load during cold snaps, request model-specific capacity and efficiency data at the outdoor temperatures relevant to your location. Do not compare cold-climate systems using minimum operating temperature alone.
Rank #2
- 𝒀𝒆𝒂𝒓-𝑹𝒐𝒖𝒏𝒅 𝑪𝒐𝒎𝒇𝒐𝒓𝒕 𝒘𝒊𝒕𝒉 𝑷𝒐𝒘𝒆𝒓𝒇𝒖𝒍 𝑰𝒏𝒗𝒆𝒓𝒕𝒆𝒓 𝑻𝒆𝒄𝒉:Experience efficient cooling in summer and cozy heating in winter. Our 1.5 Ton split AC features advanced inverter technology and a robust heat pump, delivering optimal temperatures while helping reduce energy use. Suitable for year-round climate control.
- 𝑾𝒊𝒅𝒆-𝑨𝒓𝒆𝒂 𝑪𝒐𝒗𝒆𝒓𝒂𝒈𝒆 & 𝑬𝒄𝒐-𝑺𝒎𝒂𝒓𝒕 𝑹𝒆𝒇𝒓𝒊𝒈𝒆𝒓𝒂𝒏𝒕: Easily cool or heat rooms up to 1250 sq.ft. This split air conditioner uses R32 refrigerant, which has a lower global warming potential compared to some traditional refrigerants. For refrigerant refills, local dealers can provide assistance.
- 𝑽𝒆𝒓𝒔𝒂𝒕𝒊𝒍𝒆 𝑭𝒖𝒏𝒄𝒕𝒊𝒐𝒏𝒔 𝒇𝒐𝒓 𝑪𝒖𝒔𝒕𝒐𝒎 𝑪𝒐𝒎𝒇𝒐𝒓𝒕: This air conditioner offers 5 different modes—Cooling, Heating, Auto, Fan, and Dry—allowing you to customize your environment. Plus, with 4 fan speeds and additional features like a 24-hour timer, Sleep Mode, Eco Mode, and Turbo Boost, you can enjoy convenience and efficiency tailored to your needs.
- 𝑾𝒉𝒊𝒔𝒑𝒆𝒓-𝑸𝒖𝒊𝒆𝒕 𝑶𝒑𝒆𝒓𝒂𝒕𝒊𝒐𝒏: Operates with minimal noise, so you can enjoy peace and tranquility. Whether working, sleeping, or relaxing, it helps create a quiet, disturbance-free environment—ideal for bedrooms, offices, or living rooms.
- 𝑩𝒖𝒊𝒍𝒕-𝑰𝒏 𝑴𝒊𝒍𝒅𝒆𝒘 𝑷𝒓𝒐𝒕𝒆𝒄𝒕𝒊𝒐𝒏 & 𝑺𝒆𝒍𝒇-𝑫𝒆𝒇𝒓𝒐𝒔𝒕𝒊𝒏𝒈: To maintain performance, the unit includes an anti-mildew function that helps keep internal components clean. It also features an automatic defrost function to prevent ice buildup, ensuring smooth operation even in colder climates.
What features and controls are listed?
The product listing describes cooling, heating, dry, fan, sleep, and ECO modes; four fan speeds; app and Alexa controls; washable filters; a 24-hour timer; and a self-cleaning function. These features have not been independently evaluated for app reliability, voice-control performance, noise, cleaning effectiveness, or energy use. If app compatibility or local service support is important, confirm the details for the exact model before purchase.
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1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsWhat comes in the package—and who should install it?
Costway lists a remote, wall-mounting bracket, 13-foot copper line set, 15-foot communication wire, 6.5-foot drain hose, wall sleeve, tape, putty, and user guide. The included items do not establish that the system is suitable for a particular installation or that the line-set length will work for the site. Costway’s listing says, “Note: the installation should be done only by professionals.”
Rank #3
- Year-round Comfort: This mini split air conditioner offers 18000 BTU of summer cool and 18700 BTU of winter warmth, covering up to 1250 sq ft. Flip through 7 modes (cool, heat, dry, fan, auto, sleep, ECO) and 5 fan speeds (low, mid, high, turbo, auto) for a perfectly tailored breeze every season.
- Higher Energy Efficiency: This advanced inverter mini split air conditioner precisely adjusts compressor speed and constantly fine-tunes output, featuring 19 SEER2 cooling and 9 HSPF2 heating. It ensures lower costs compared to conventional units. GWP of air conditioning refrigerants is 675.
- User-friendly Design: Featuring chassis electrical heating, the outdoor unit is built for extreme weather use, which can cool even at 118.4℉or Heat even at 5℉. The handy remote control with an 26 ft effective control distance lets you easily adjust the modes, speeds, timer, swing 4D airflow across the room, switch between ℃/℉ and more.
- Ultra Quiet Operation: Running at a low noise of 23 dB and paired with a sleep mode and display off function, this mini split ac unit allows you to enjoy a peaceful sleep. Besides, the built-in 24H timer provides customizable scheduling while saving energy.
- Easy Maintenance & Reliable Use: Maintenance is a breeze thanks to the 58℃/137℉ self-cleaning function and removable & washable filters. In addition, this mini split air conditioner and heater features a child lock that stops tiny fingers from messing with your climate settings, while the auto defrost keeps winter performance ice-free. Note: the installation should be done only by professionals.
Before ordering, ask an installer to review the complete installation manual and equipment nameplate, and confirm:
- Whether the system’s capacity suits the calculated heating and cooling load.
- Required circuit size, overcurrent protection, disconnect, and wiring; 208–230V alone does not establish electrical compatibility.
- Whether the listed line set, communication wire, and drain routing work at the chosen locations.
- Outdoor-unit mounting, service access, condensate management, and any local code requirements.
- The full installed price, including electrical work, mounting, commissioning, and any work or materials not included in the package.
What should you verify about certification, rebates, and warranty?
The Costway product page claims ENERGY STAR, ETL, and AHRI certifications, but matching independent registry records were not established. Check the exact indoor and outdoor model numbers in the relevant certification directories before relying on a badge for compliance or rebate eligibility. Also check the rules for your location and program; a product-page claim alone does not guarantee a rebate.
Rank #4
- [ENERGY EFFICIENT COOLING] This 19 SEER2, 208V~230V, 18000 BTU/h, ETL Listed, Maximum Fuse Size is 15A. AHRI Certified pre-charged air conditioner unit features a ductless mini split inverter plus system with a heat pump and DC Inverter technology provides up to 30% power savings.
- [STRONG SYSTEM] This air conditioner is designed with several smart functions that make it easy to use: 4D air flow(up-down left-right), I feel mode, 24 hour timer, sleep mode, eco energy saving mode, multiple fan speeds, turbo function, heating, cooling dehumidifying and dry modes.
- [AMPLE COVERAGE] This unit is filled with the new R-32 refrigerant to ensure cleaner air quality indoors and outdoors, providing cooling and heating for up to 1000 sq. ft. The outdoor condenser comes with an upgraded bottom heating element, delivering efficient performance even in temperatures as low as 5°F. Competitors use an older refrigerant that is more harmful to the environment. If additional refrigerant needs to be added to the lines, check R-32 availability at your local seller.
- [SMART SENSOR] It adjusts airflow and temperature accordingly, resulting in the ultimate in personal comfort control and energy savings. The unit will sense room temperature at the remote control, instead of at the indoor unit during cooling mode.Full 16ft copper line (Standard size 1/4" & 1/2" outer dimension copper pipes) and 6.56ft outlet drain pipe (inner/outer diameter size: 15.5mm/16.9mm) installation kit included.
- [QUIET OPERATION] This air conditioner is ultra silent at only 29 dBa. Line-set vacuuming is required during installation. The unit provides equal airflow in every part of your room and can adjust to 60-90 degrees Fahrenheit to suit your comforts in just a few minutes.
Compare written installation quotes and review the current warranty terms for the exact model before buying. The available product-page information does not establish the full applicable warranty conditions, and those terms can matter as much as the equipment price when comparing systems.
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Use a like-for-like comparison rather than relying on headline capacity or efficiency figures alone:
Best Value
- [Energy Efficient Cooling & Heating:]Equipped with a high power compressor and 1.5 ton heat pump, this AHRI Certified pre-charged ac unit allows you to enjoy the convenience of cooling in summer and warming in winter. Besides, with an innovative inverter technology, the air conditioner changes the power supply frequency without frequently turning the compressor on and off. GWP of air conditioning refrigerants is 675.
- [5 Modes for All-Year Comfort:]This 18000 BTU split-system AC unit has 5 working modes for you to choose from: auto, cool, dry, heat and fan mode. In addition, this split air conditioner also comes with 4 available fan speeds (low/medium/high/auto), sleep mode, ECO mode, iFEEL & turbo function to meet various needs.
- [Easy Control & Quiet Operation:]The handy remote control enables you to control this mini split AC unit from your comfortable bed or sofa conveniently. The smart 0.5-24 hour timer and low-noise operation ensure a peaceful sleep time. What's more, the display screen on the remote control will be turned off automatically when there is no operation within 10s, which will not disturb your sleep.
- [Self Cleaning & Auto Defrost:]Designed with a self-cleaning function at high temperature of 134.6℉ and a washable filter, this split air conditioner can automatically clean its interior. Moreover, the outdoor unit features an auto-defrost function to avoid damage and improve energy efficiency.
- COSTWAY's superior quality and design are backed by an industry-leading manufacturer's warranty. This warranty covers 5 years of parts replacement and 8 years of compressor coverage, ensuring customers can rely on our products for years to come. In addition to this, the installation of this equipment should be done only by a Licensed HVAC Installer.
- Cold-weather output: Compare heating capacity and efficiency at the outdoor temperatures your home actually encounters.
- Efficiency: Match SEER2 and HSPF2 ratings to the exact equipment combination; do not translate a rating directly into promised bill savings.
- Installation fit: Check voltage and nameplate requirements, line-set constraints, condensate routing, and commissioning needs with an installer.
- Total cost and support: Compare written installed quotes, warranty terms, replacement-part access, and the availability of local technicians familiar with the equipment.
- Certification: Verify exact model numbers in certification and local rebate records rather than assuming a listing badge settles eligibility.
Who should consider it?
The SEERXtreme is worth getting a quote for if its listed capacity and features appear relevant to your project and a qualified installer can verify the design, electrical fit, and total cost. It is a weaker choice to buy on the strength of the 1,250-square-foot estimate, the −13°F operating claim, or certification badges alone. If reliable heat at very low temperatures is essential, make model-specific cold-weather capacity data a condition of your comparison.
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Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
