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Ductless Mini-Split AC & Heat Pump Systems | San Francisco & Marin

Mini System

Air Conditioning

In summer, air conditioners work to provide cooling and dehumidification. They extract heat from inside the home and transfer it outside. AC typically use a vapor compression cycle. This cycle circulates a refrigerant, a material that increases in temperature significantly when compressed and cools rapidly when expanded. The exterior portion of a typical AC is called the condensing unit and houses the compressor, the noisy part that uses most of the energy, and the condensing coil. An air-cooled condensing unit should be kept free from plants and debris that might block the flow of air through the coil or damage the thin fins of the coil. Ideally, the condensing unit should be located in the shade. However, do not block air flow to this unit with dense vegetation, fencing or overhead decking. The inside mechanical equipment, called the air-handling unit, houses the evaporator coil, the indoor blower, and the expansion, or throttling valve. The controls and ductwork for circulating cooled air to the house complete the system.

What is a ductless mini split air conditioner systems?

Mini split systems have no ducts. They have two main components, an outdoor compressor and an indoor air-handling unit. The two units are linked by a conduit which stores the power cable, suction tubing, refrigerant tubing and a condensate drain. Indoor units can be wall or ceiling mounted. Ductless splits can be used to cool one zone or multiple zones applying two to four indoor units to one condenser. The indoor units can all be used independently of each other.

How to Choose a Ductless Split Air Conditioner: A Practical Guide

Choosing the right ductless split air conditioner, also known as a mini-split, can greatly improve your indoor comfort, energy efficiency, and even long-term cost savings. With so many options on the market, selecting the right system might feel overwhelming. This guide breaks down the key factors to consider when choosing a ductless split air conditioner for your home or business.

  1. Determine Your Cooling (and Heating) Needs. Start by identifying the square footage of the space you want to condition. Ductless mini-splits are available in a range of capacities, usually measured in BTUs (British Thermal Units). See BTU chart based on room size.

    2. Tip: Oversizing or undersizing your unit can lead to inefficiency, discomfort, or higher energy bills. A professional load calculation is ideal.

  2. Choose Between Single-Zone and Multi-Zone Systems.
    • Single-Zone Systems: Best for conditioning a single room or isolated space.
    • Multi-Zone Systems: Can connect one outdoor unit to 2–8 indoor units, ideal for whole-home or multi-room climate control.

      • Tip: If you're planning to add more rooms in the future, opt for a system that supports expandability.

  3. Check the Energy Efficiency Ratings. Look for systems with high SEER (Seasonal Energy Efficiency Ratio) and HSPF (Heating Seasonal Performance Factor) ratings.
    • SEER: Higher SEER = better cooling efficiency. Look for a SEER rating of 16 or higher.
    • HSPF: Relevant if your system will also heat. HSPF of 8 or higher is considered efficient.

      • Energy Star–certified models typically offer excellent efficiency and long-term savings.

  4. Consider the Type of Indoor Unit. Ductless indoor units come in several styles:
    • Wall-Mounted: Most common and easiest to install.
    • Ceiling Cassette: Recessed into the ceiling—great for commercial or modern designs.
    • Floor-Mounted: Suitable for areas with limited wall space.
    • Concealed Ducted: Hidden from view and connected to short duct runs.

      • Choose the style that best fits your space, layout, and design preferences.

  5. Look for Smart Features and Controls. Many mini-splits now come with Wi-Fi connectivity, smart thermostats, and mobile app control, allowing you to adjust settings remotely. These features enhance convenience and can help you manage energy use more effectively.
  6. Check Noise Levels. If quiet operation is important (e.g., for bedrooms or offices), compare the decibel (dB) ratings of different models. Many ductless systems operate as quietly as 19–30 dB-quieter than a whisper.
  7. Assess the Brand Reputation and Warranty. Stick with well-known, reliable brands like Mitsubishi, Daikin, Fujitsu, LG, or Panasonic. Look for:
    • Comprehensive warranties (5–12 years is common)
    • Local service availability
    • Positive customer reviews and support
  8. Professional Installation Is a Must. Even if you're handy, ductless split systems should be installed by a licensed HVAC technician. Proper installation ensures:
    • System performance and efficiency
    • Manufacturer warranty validity
    • Correct refrigerant charge and electrical setup
  9. Consider Climate Conditions. If you live in an area with harsh winters, make sure your system has low-temperature heating capabilities. Look for models labeled “Hyper-Heat” or “cold-climate mini-split” for reliable year-round performance.
  10. Budget Accordingly. Prices vary based on:
    • System capacity
    • Number of zones
    • Indoor unit type
    • Brand
    • Installation complexity

      • Expect to pay between $2,000–$5,000 for a single-zone system (installed), and $5,000–$12,000+ for multi-zone setups.

Where can mini-splits be used?

Mini-split systems - also known as ductless mini-splits - are incredibly versatile HVAC solutions that can be used in a wide variety of settings. Because they don’t require ductwork and can be independently controlled, they’re ideal for both residential and commercial applications. Mini-splits can be used almost anywhere you need effective, flexible, and efficient heating and cooling. Their ease of installation, zone control, and ability to work without ducts make them an excellent choice for a wide range of applications - from individual rooms to whole homes and commercial buildings. Whether you’re upgrading your comfort or planning a new space, mini-splits offer a smart solution tailored to your specific needs. Here are some of the most common (and effective) places to use mini-splits:

  1. Homes Without Existing Ductwork
    Older homes or historic buildings that were built before central HVAC systems became standard often lack ductwork. Installing a mini-split allows for heating and cooling without the need for costly renovations or tearing into walls.
  2. Room Additions or Renovations
    When you add a sunroom, garage conversion, or new room to your home, extending existing ductwork can be expensive or impractical. Mini-splits offer a simple, independent solution that can be installed quickly and without disrupting the rest of your HVAC system.
  3. Apartments, Condos, and Multi-Family Homes
    In multi-unit buildings, it’s often difficult to retrofit a central system for every tenant. Mini-splits allow for zoned comfort in each unit, giving residents control over their own temperature without interfering with their neighbors.
  4. Basements and Attics
    These areas are notoriously hard to keep comfortable due to their insulation challenges and location in the home. Mini-splits provide focused heating and cooling without requiring a connection to your home’s central system.
  5. Garages and Workshops
    If you use your garage or workshop year-round, a mini-split is a great way to keep the space comfortable without conditioning the entire home. Plus, many mini-splits offer both heating and cooling, which is ideal for these multipurpose areas.
  6. Home Offices and Studios
    Spending long hours in a small space like a home office or art studio? A mini-split gives you precise control over the temperature, ensuring comfort and energy efficiency without adjusting the settings for the rest of the home.
  7. Server Rooms or IT Closets
    Small commercial spaces like server rooms or IT closets often require constant cooling. Mini-splits provide targeted climate control without compromising the comfort of the rest of the office.
  8. Commercial Spaces
    Retail stores, restaurants, clinics, salons, and other commercial establishments benefit from the flexibility and zone control mini-splits offer. They can be installed in individual rooms, suites, or open-concept spaces without the need for extensive ductwork.
  9. Vacation Homes and Guesthouses
    Mini-splits are ideal for spaces that are used part-time or seasonally. You can turn them on only when needed, reducing energy waste and lowering utility bills compared to running a full HVAC system for an unoccupied space.
  10. Energy-Efficient Homes
    In homes designed to be energy-efficient or net-zero, mini-splits are a perfect match. They offer excellent performance with high SEER ratings and can be paired with renewable energy sources like solar panels for even greater efficiency.
BTU chart based on room size
Area (ft²) BTU's Required
100 to 150 5,000 BTUs
150 to 250 6,000 BTUs
250 to 300 7,000 BTUs
300 to 350 8,000 BTUs
350 to 400 9,000 BTUs
400 to 450 10,000 BTUs
450 to 550 12,000 BTUs
550 to 700 14,000 BTUs
700 to 1,000 18,000 BTUs
1,000 to 1,200 21,000 BTUs
1,200 to 1,400 23,000 BTUs
1,400 to 1,500 24,000 BTUs
1,500 to 2,000 30,000 BTUs
2,000 to 2,500 34,000 BTUs
Add 20% BTUs for ceilings higher than 8 ft. and poorly insulated areas
Add 30% BTUs for climates with seasonal temperatures over 90℉

Multi zone ductless mini split system.

The Ductless Multi-Zone Mini Split Air Conditioners allow you to enjoy ideal levels of comfort in the rooms you use most. Each room (zone) operates independently with its wireless/wired remote control. People in different rooms – the kitchen, master bedroom, or living room – can enjoy temperature settings that make each room most comfortable. Plus, you have the option of not heating or cooling rooms that are not being used. If you’re looking for a complete comfort solution for several different rooms, the multi-zone system is the right choice. The system is flexible enough to conform to a particular cooling and heating need and offers numerous different indoor unit combinations.

Advantages of Ductless Air Conditioners

Many models can have as many as four indoor air handling units (for four zones or rooms) connected to one outdoor unit. The number depends on how much heating or cooling is required for the building or each zone (which in turn is affected by how well the building is insulated). Each of the zones will have its own thermostat, so you only need to condition that space when it is occupied, saving energy and money.

Don't waste money cooling and heating the ducts in your walls and attic. Mini-split systems are ductless, meaning they install easily and won't take up valuable closet space. Since mini-splits have little to no ducting, they forego those energy losses typically associated with central forced-air systems. Duct losses in a central air system can easily account for more than 30% of energy consumption, especially if the ducts are not sealed tight or in an unconditioned space such as an attic or crawlspace.

Mini splits offer flexibility because they can be suspended from a ceiling, mounted flush behind a drop ceiling, hung on a wall or floor-standing. Ductless heat pumps allow for a peaceful inside environment by enabling the contractor to install components like compressors and motors outdoors.

Installing a traditional, ducted system can take several weeks and disrupts daily activities in the home. Ductless systems are far less invasive to install, and depending upon the number of indoor and outdoor units required, can be up and running in as little as one day.

Multi-split systems run on small pipes that require a mere three-inch hole. That means homeowners don’t have to worry about rebuilding walls or ceilings around ductwork and there is no loss of precious square footage.

Often, the quality of indoor air can be lower than the quality of outdoor air. With traditional HVAC systems, air ducts must be professionally cleaned on a regular basis, and even after cleaning, dust and allergens are left behind. Ductless systems, on the other hand, offer multi-stage filtration that can drastically reduce dust, bacteria, pollen, allergens and other particulates in the air.

Due to the lack of combustion the mini-splits have a low fire risk.

Disadvantages of Ductless Air Conditioners

The primary disadvantage of mini splits is their cost. Such systems cost about $2,500 to $4,000 per ton (12,000 Btu per hour) of cooling capacity. This is about 30% more than central systems (not including ductwork) and may cost twice as much as window units of similar capacity.

Proper system sizing and installation is critical to getting the touted benefits from a ductless system. A mini split installation is not easy for the common homeowner. It will take a qualified HVAC contractor to come out to a home, assess the space and determine whether or not such a system can be installed.

Many homeowners are hesitant to install ductless because the units aren’t necessarily design-friendly. They come in standard white or beige and can’t be covered. But in our experience, ductless customers who are initially reluctant because of aesthetics report that after installation, they forget the unit is even there.

To maintain your system, you’ll have to wash each unit’s filter monthly (more often if you smoke or have pets). Don’t skip it: ductless fans can’t handle accumulating debris, and if you ignore maintenance and a professional cleaning is required, you’ll spend hundreds of dollars and possibly shorten the life of your system.
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