Della Vario 12000 BTU Review: 115V Smart Mini Split
Della's best-selling Vario mini split in a 1 ton, 115V size: 20.5 SEER2, Wi-Fi and Alexa control, heat pump operation down to -4F and a 16.4 ft install kit.
By Daniel Brooks
Updated October 22, 2026
The Della Vario 12000 BTU is a 1 ton, 115 volt mini split heat pump with Wi-Fi and Alexa control built in. Della rates it for up to 550 square feet, lists 20.5 SEER2, and says the heat pump keeps working down to -4F, which is colder than most budget systems handle. It is the best-known Della model in our single-zone mini-split air conditioners category, with a 4.4 out of 5 average from 1,470 ratings shared across the Vario series.
Our Verdict
The Vario 12000 BTU is a well-balanced smart mini split for a bedroom, office or small living room. You get app and voice control, an I Feel sensor in the remote, 4D airflow, a full set of modes and a complete installation kit. The -4F heating rating is a real advantage in places with cold snaps.
It needs professional installation with a vacuum on the line set, and it costs more than basic remote-only systems. Della’s Wi-Fi also supports 2.4 GHz networks only, which matters if your router broadcasts 5 GHz alone.
Della Vario 12000 BTU 115V Mini Split AC with Heat
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Key Specifications
| Feature | Specification |
|---|---|
| Brand | Della |
| Model | TL-12K1VB-21S-I+O (Vario Series) |
| Type | Single-zone ductless mini split heat pump |
| Cooling Capacity | 12000 BTU/h (1 ton) |
| Heating Capacity | 12000 BTU/h |
| Room Size | Up to 550 sq ft |
| Power | 110-120V (115 volts) |
| Rated Wattage | 1130 watts |
| Max Fuse Size | 25A |
| Efficiency | 20.5 SEER2 |
| Heat Pump Range | Down to -4F |
| Noise Level | 28 dBA (listed) |
| Refrigerant | R-454B |
| Line Set | 16.4 ft kit, 1/4 and 3/8 inch copper |
| Controls | Remote, Della+ app, Alexa |
Cooling Capacity and Room Size
Della rates the Vario 12000 BTU for up to 550 square feet, which matches the top of the 12,000 BTU band in the ENERGY STAR chart below. That is a realistic figure, so the system should hold temperature well in a primary bedroom, a home office or a living room of that size. Della’s own sizing guide makes the same point: about 9000 BTU for a 400 square foot room, 12000 BTU for 550 and 18000 BTU for 1000.
ENERGY STAR publishes this general guide for matching cooling capacity to floor area:
| Room Size (sq ft) | Cooling Capacity (BTU/hr) |
|---|---|
| 100 to 150 | 5,000 |
| 150 to 250 | 6,000 |
| 250 to 300 | 7,000 |
| 300 to 350 | 8,000 |
| 350 to 400 | 9,000 |
| 400 to 450 | 10,000 |
| 450 to 550 | 12,000 |
| 550 to 700 | 14,000 |
| 700 to 1,000 | 18,000 |
| 1,000 to 1,200 | 21,000 |
| 1,200 to 1,400 | 23,000 |
| 1,400 to 1,500 | 24,000 |
| 1,500 to 2,000 | 30,000 |
| 2,000 to 2,500 | 34,000 |
Adjust for your room: reduce capacity by 10 percent for a heavily shaded room, increase it by 10 percent for a very sunny room, add 600 BTU for each regular occupant beyond two, and add 4,000 BTU if the unit cools a kitchen. Source: ENERGY STAR.
The inverter compressor adjusts its speed to the load, and Della claims up to 30 percent power savings from the DC inverter design. You can set temperatures from 60 to 90F.
Heating Performance
Heating capacity matches cooling at 12000 BTU/h, and Della says the heat pump works in outdoor temperatures as low as -4F. That puts the Vario ahead of the many budget systems rated only to 5F, and it makes the unit a practical primary heat source for its zone through most winters outside the far north. Defrost protection keeps the outdoor coil clear in cold, damp weather.
Smart Control
The Vario connects to the free Della+ app for schedules, a timer, mode changes and geo-location, and it works with Alexa for voice control. The included remote has an I Feel sensor that reads the temperature where you sit, so the system adjusts airflow and temperature for your spot rather than the wall near the ceiling. Della’s Wi-Fi supports the 2.4 GHz band only.
Modes and Airflow
You get cooling, heating, dry mode for dehumidifying, sleep mode, eco energy saving mode, turbo, multiple fan speeds and a 24 hour timer. The 4D airflow moves the louvers both up and down and left and right, so the air spreads evenly across the room instead of blowing in one stream.
Noise
Della lists the Vario at 28 dBA, which is very quiet at low speed. The product specifications show a higher maximum figure of 42 dB, which is what you can expect at high fan. Either way, it is far quieter than a window unit.
Installation
Della is clear that this is not a DIY mini split. The outdoor unit is pre-charged, and the kit includes standard 1/4 and 3/8 inch copper lines and a 78.7 inch drain pipe, but the line set must be vacuumed during installation and any change in line length requires adjusting the refrigerant charge. Della recommends professional HVAC installation and offers a rental tool kit for vacuuming.
Plan for a dedicated 115 volt circuit with a maximum fuse size of 25A.
Warranty
Della offers lifetime parts coverage if you register the system within 100 days. Licensed HVAC installs receive enhanced coverage, while non-licensed installs get a limited version. Labor is not included.
Della Vario vs Other Della Series
Della sells several 12000 BTU lines side by side. The Vario is the mainstream choice, with 20.5 SEER2, -4F heating and the largest ratings base. The Motto and Econo series cost less and trim efficiency, while the Serena and Optima lines push efficiency higher and add ENERGY STAR certification. For most buyers on a 115 volt circuit, the Vario hits the best balance of price, efficiency and smart features.
Planning the Install
Choose an indoor spot high on an outside wall with open space in front of the unit, and an outdoor location within reach of the 16.4 ft kit that is level and well drained. If the run needs to be longer, the installer will have to add refrigerant, so a direct path saves both time and money. Ask for the electrical work, including a dedicated circuit and outdoor disconnect, to be quoted with the install.
Maintenance
Della recommends cleaning the reusable filters seasonally, inspecting the indoor and outdoor coils, and keeping the area around the outdoor unit clear. In heavy summer use, rinsing the filters every few weeks will keep airflow and efficiency up.
Pros and Cons
| Pros | Cons |
|---|---|
| Wi-Fi app and Alexa control | Professional installation required |
| Heat pump works down to -4F | Wi-Fi supports 2.4 GHz only |
| 20.5 SEER2 on 115 volts | Costs more than remote-only rivals |
| Quiet 28 dBA listing | Ratings shared across the series |
| Lifetime parts coverage when registered | Labor not covered |
Who Should Buy It
| Who Should Buy It? | Who Should Look Elsewhere? |
|---|---|
| Smart home users | DIY installers |
| Homes with cold snaps | Rooms well over 550 sq ft |
| Bedrooms and home offices | Buyers who want the lowest price |
| Homes without spare panel capacity | 5 GHz only Wi-Fi networks |
For more options, see our picks for the best smart mini-split air conditioners and the best 115V mini-split air conditioners.
Final Verdict
The Della Vario 12000 BTU is a smart, efficient mini split for one room up to 550 square feet. It runs on 115 volts, heats down to -4F and adds app and Alexa control without a separate kit. You can check the current price and details for the Della Vario 12000 BTU 115V Mini Split AC with Heat Pump.
Frequently Asked Questions
Does the Della Vario 12000 BTU have Wi-Fi?
Yes. It works with the Della+ app and Alexa on 2.4 GHz Wi-Fi.
How cold can it heat?
Della rates the heat pump for operation down to -4F.
What size room does it cover?
Della rates it for up to 550 square feet.
Is it a DIY mini split?
No. The line set must be vacuumed, and Della requires professional installation.
About the author
Daniel Brooks is a home cooling editor at WikiCooling, covering window, portable, through-the-wall and mini-split air conditioners, fans, and dehumidifiers. He researches cooling capacity, energy efficiency, noise levels, installation requirements, and buyer feedback to help homeowners choose the right unit for their room size, climate, and budget.