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Choosing between a 450 sq ft vs 750 sq ft mini split air conditioner depends on your room size. Both units offer year-round heating and cooling with inverter technology for energy efficiency. They share a 19 SEER2 rating and white finish. The main difference is capacity. One covers 450 square feet with 9100 BTU. The other handles 750 square feet with 12000 BTU. Select the right size for your space.
Coverage Area
450 Sq. Ft.
750 Sq. Ft.
Cooling Capacity
9100 BTU
12000 BTU
Heating Capacity
9200 BTU
12500 BTU
Voltage
208-230V
115V/110V
Indoor Unit Weight
17.6 pounds
92 pounds
Indoor Unit Height
7.91 inches
8.7 inches
Choose the first if
- You have a smaller room up to 450 square feet.
- You need a 208-230V electrical connection.
- You prefer a lighter indoor unit that is easier to mount.
Choose the second if
- You need to cool or heat a larger space up to 750 square feet.
- You only have a standard 115V/110V outlet available.
- You want a unit with an 8-year warranty included.
Verdict
Pick the COSTWAY model if your space is under 450 square feet and you have a 230V circuit. Choose the Rellytech unit if you need to cover up to 750 square feet or only have 115V power. Both units provide efficient climate control for their respective sizes.
Coverage and Power Specs Compared
Coverage area
Edge: Rellytech 12,000 BTU 115V Mini Split
The COSTWAY 9100 BTU Mini Split is rated for up to 450 square feet. This makes it suitable for smaller bedrooms or home offices where heat loss is minimal. In contrast, the Rellytech 12,000 BTU 115V Mini Split covers up to 750 square feet. This larger capacity handles bigger living spaces, open-plan areas, or garages with greater ease. You should choose the Rellytech unit if your space exceeds 450 square feet. The higher BTU output ensures consistent temperatures across the wider area without overworking the compressor.
Cooling capacity
Edge: Rellytech 12,000 BTU 115V Mini Split
The COSTWAY unit provides 9100 BTU of cooling power. This output is sufficient for the stated 450 square feet but offers less margin for error in very hot climates. The Rellytech model delivers 12,000 BTU of cooling. This significant increase in capacity allows it to handle higher heat loads more effectively. If you live in a region with intense summer temperatures, the extra 2900 BTU from the Rellytech unit provides a buffer. It ensures the room cools down faster and maintains the set temperature more reliably during peak heat.
Heating capacity
Edge: Rellytech 12,000 BTU 115V Mini Split
Both units offer heating functions, but the output differs. The COSTWAY Mini Split provides 9200 BTU of winter warmth. This is slightly higher than its cooling capacity, which is typical for heat pump efficiency. The Rellytech unit offers 12,500 BTU of heating power. This is the highest heating output among the two. For colder months, the Rellytech model can recover the room temperature faster. If heating is your primary concern or you live in a colder zone, the Rellytech unit provides more robust warmth for the larger coverage area.
Operating modes
Edge: COSTWAY 9100 BTU Mini Split
The COSTWAY unit features seven distinct operating modes. These include cool, heat, dry, fan, auto, sleep, and ECO. This variety allows you to fine-tune the environment for specific needs, such as dehumidifying in humid weather or running just the fan for air circulation. The Rellytech unit offers four modes: cooling, heating, fan, and dry, plus an ECO function. While the Rellytech modes cover the essentials, the COSTWAY unit provides more granular control. If you prefer detailed customization of your climate settings, the COSTWAY unit is the better choice.
Fan speeds
Edge: COSTWAY 9100 BTU Mini Split
Airflow customization is handled differently by each unit. The COSTWAY Mini Split includes five fan speeds: low, mid, high, turbo, and auto. The inclusion of a turbo setting allows for rapid air circulation when you need quick cooling or heating. The Rellytech unit provides four fan speeds: high, medium, low, and auto. While this covers standard needs, it lacks a dedicated turbo option. If you value the ability to blast air at maximum speed to clear out stagnant air quickly, the COSTWAY unit offers more flexibility in its fan settings.
Pick the right mini split for you
Small room owner needing quiet operation
Our pick: COSTWAY 9100 BTU Mini Split
This unit covers 450 sq ft with 9100 BTU cooling. It runs at just 23 dB, making it ideal for bedrooms where silence matters. The 4D swing and sleep mode enhance comfort in tight spaces without disturbing your rest.
Larger space user needing 115V power
Our pick: Rellytech 12,000 BTU 115V Mini Split
This model handles 750 sq ft with 12,000 BTU cooling. It operates on standard 115V electricity, fitting typical household outlets. The 12,500 BTU heating output ensures your larger room stays warm during colder months without requiring specialized electrical wiring.
User wanting wide airflow control
Our pick: COSTWAY 9100 BTU Mini Split
This unit features 4D airflow swing for wider coverage within its 450 sq ft limit. It offers seven operating modes and five fan speeds. The remote control works up to 26 ft away, allowing easy adjustments from across the room.
| # | Product | Best for | Price |
|---|---|---|---|
| 1 | COSTWAY 9100 BTU Mini Split | 450 sq ft rooms with 230V power | |
| 2 | Rellytech 12,000 BTU 115V Mini Split | Cooling and heating 750 square foot rooms |
COSTWAY 9100 BTU Mini Split
Best for: 450 sq ft rooms with 230V power
- Coverage Area
- 450 Sq. Ft.
- Cooling Capacity
- 9100 BTU
- SEER2 Rating
- 19 SEER2
- Voltage
- 208-230V
- Smart Compatibility
- Remote control
- Operating Modes
- Cool, heat, dry, fan, auto, sleep, ECO
This COSTWAY mini split delivers 9100 BTU of cooling and 9200 BTU of heating for spaces up to 450 sq ft. It runs on 208-230V power with a 19 SEER2 efficiency rating. The unit features an inverter compressor and 7 operating modes. You get 4D airflow and ultra-quiet operation at 23 dB. This system is designed for wall mounting and includes a remote control for easy adjustments.
- Covers up to 450 sq ft with 9100 BTU cooling
- High 19 SEER2 energy efficiency rating
- Operates quietly at just 23 dB
- Includes 4D swing airflow and 7 modes
- Lower 9100 BTU capacity compared to 12000 BTU competitors
- Requires 208-230V voltage instead of standard 115V
- Heavier at 17.6 pounds than lighter 115V models
- You need cooling for a room up to 450 sq ft
- You have a 208-230V electrical circuit available
- You want high energy efficiency with 19 SEER2
- You only have standard 115V outlets
- You need to cool a space larger than 450 sq ft
- You prefer a lighter unit under 15 pounds
Verdict: COSTWAY 9100 BTU Mini Split fits users with 208-230V power who need efficient cooling for rooms up to 450 sq ft. It offers quiet operation and high SEER2 ratings for those prioritizing energy savings.
Rellytech 12,000 BTU 115V Mini Split
Best for: Cooling and heating 750 square foot rooms
- Coverage Area
- 750 Sq. Ft.
- Cooling Capacity
- 12,000 BTU
- SEER2 Rating
- 19
- Voltage
- 115V/110V
- Operating Modes
- cooling, heating, fan, dry, ECO, Sleep
- Features
- Inverter
The Rellytech 12000 BTU mini split handles cooling and heating for spaces up to 750 square feet. It runs on 115V power with a 19 SEER2 rating for efficiency. The unit offers four operating modes and four fan speeds. It measures 31.9 inches wide and weighs 92 pounds. This system suits larger rooms like living areas or garages where consistent temperature control is needed.
- Covers up to 750 square feet
- 19 SEER2 energy efficiency rating
- Four fan speeds and 90-degree vertical swing
- Quiet operation at 42dB
- Heavier build at 92 pounds
- Lower SEER2 rating than the 20 SEER2 alternative on the list
- You need to cool or heat a 750 square foot room
- You want a 115V unit for standard outlets
- You prefer quiet operation under 45dB
- You only need to cover 450 square feet
- You want the highest efficiency rating available
- You need a lighter, more compact indoor unit
Verdict: Rellytech 12000 BTU Mini Split AC fits those who need strong cooling for larger spaces up to 750 square feet. It offers reliable performance for living rooms or garages, though it is heavier and slightly less efficient than the top SEER2 option.
Specifications side by side
| Spec | COSTWAY 9100 BTU Mini Split | Rellytech 12,000 BTU 115V Mini Split |
|---|---|---|
| Cooling Capacity | 9100 BTU | 12,000 BTU |
| Coverage Area | 450 sq ft | up to 750 sq. ft. |
| SEER2 Rating | 19 SEER2 | 19 |
| Voltage | 208-230V | 115V/110V |
| Smart Compatibility | Remote control | – |
| Operating Modes | Cool, heat, dry, fan, auto, sleep, ECO | cooling, heating, fan, dry, ECO, Sleep |
| Features | Inverter | Inverter |
| Color | White | White |
| Operating Mode | Heater | – |
| SEER Rating | 19 SEER2 | 19 SEER2 |
| Mounting Type | Wall-Mounted | – |
| Dimensions | 11.5 × 31.2 × 7.91 inches | 8.23 × 32.3 × 11.9 inches |
| Weight | 17.6 pounds | 92 pounds |
| Size | 9100BTU, 208-230V, 19 SEER2 | 12000BTU,115V,19 SEER2 |
| Model | 11090-CYFP | CE0-1 |
Frequently asked questions
Can a 450 sq ft mini split cool a 750 sq ft room?
No, it cannot. The COSTWAY 9100 BTU Mini Split is rated for up to 450 square feet. Using it in a larger space will result in poor cooling performance. You need a unit with higher BTU output, like the 12,000 BTU Rellytech model, to effectively manage the air volume in a 750 square foot area.
Do both units support heating as well as cooling?
Yes, both units provide year-round climate control. The COSTWAY model operates as a heater with 19 SEER2 efficiency. The Rellytech unit also features heating modes and inverter technology. This means you can use either system for warmth in winter and cooling in summer without needing separate appliances for each season.
Is the voltage difference important for my home installation?
It is critical for safety and compatibility. The COSTWAY unit requires 230V power, which is standard for many dedicated circuits. The Rellytech model runs on 115V, fitting standard household outlets. You must verify your available electrical supply matches the specific voltage requirement of the mini split you choose to avoid installation issues.
How do the physical dimensions affect wall mounting?
Both units are designed for wall mounting but differ in weight and size. The COSTWAY unit weighs 17.6 pounds and measures 31.2 inches wide. The Rellytech unit is significantly heavier at 92 pounds with a width of 31.9 inches. Ensure your wall brackets can support the heavier Rellytech model securely.
Are both models inverter-based for energy savings?
Yes, both systems use inverter technology. This allows the compressor to adjust speed rather than cycling on and off. Both units share a 19 SEER2 rating, indicating high energy efficiency. This feature helps reduce electricity costs by maintaining your desired temperature with less power consumption compared to non-inverter systems.
Which unit is better for a garage or workshop?
The Rellytech 12,000 BTU Mini Split is better for larger, open spaces like garages. It covers up to 750 square feet and provides stronger cooling capacity. The COSTWAY unit is limited to 450 square feet and is optimized for smaller, enclosed rooms. Choose the Rellytech for larger, potentially less insulated areas.