Key Takeaways
- Attic air conditioners generally cost $100–$5,000, depending on the type and attic size.
- Ductless mini-splits are energy-efficient options, starting at $500 for single-zone systems.
- Improve ventilation, add insulation, and seal air leaks to further lower attic cooling costs.
Homeowners often find it challenging to cool attics, as they’re rarely connected to central HVAC systems. Attics overheat in the summer, thanks to the sun and rising hot, humid air throughout the home. If you plan to use the space or want to lower your home’s energy costs, you can opt for stand-alone cooling systems.
Ductless mini-splits, portable air conditioners, and window air conditioners are the best options for cooling attics. Homeowners can expect to pay between $100 and $550 for window or portable units. Single-zone ductless mini-splits range from $500 to $5,000, but you could pay up to $14,500 to install a brand-new multizone mini-split to serve your entire house. Attic fans are also an excellent choice for uninhabitable spaces, allowing you to cool the home and increase ventilation.
“The attic is the hottest room in the house,” said Mitch Rosa, owner of Hudson Valley HVAC in Orange County, New York. “Typically, it would be best to install a ductless mini-split air conditioner. They’re super quiet and super effective.”
Below, we’ve highlighted some of the top choices for attic cooling, average attic air conditioner costs, and tips for lowering your home’s energy bills.
This site receives compensation from the companies featured in this listing, which may impact where and how products appear. This listing doesn’t feature all companies, products, or offers that may be available.
This site receives compensation from the companies featured in this listing, which may impact where and how products appear. This listing doesn’t feature all companies, products, or offers that may be available.
Costs in this article are sourced from contractor estimates used by Angi and HomeAdvisor.
Typical Attic Air Conditioner Costs
Attic air conditioners cost between $100 and $14,500, depending on the type of unit you install, as well as your attic’s accessibility, ventilation, and insulation.
Window AC units typically range from $150 to $550. With no additional labor costs, they’re an affordable option as long as you have a window in your attic. Single-zone ductless mini-splits start at $500, but you could pay up to $14,500 for a new multizone system that also cools your home and attic.
You can also choose an attic fan if your space doesn’t see much use. This would lower the amount of heat reaching the attic, reducing energy bills. Attic fans and vents usually range from $400 to $900.
This table breaks down common AC systems for attics and their related costs:
| System Type | Cost Range | Best For |
|---|---|---|
| Portable AC unit | $100–$500 | Temporary use |
| Window unit | $150–$550 | Attics with window access |
| Single-zone ductless mini-split | $500–$5,000 | Finished attics and regular-use spaces |
| Multizone ductless mini-split | $2,650–$14,500 | Finished attics and regular-use spaces, part of the central system |
| Attic fan | $400–$900 | Uninhabitable attics |
| Ductwork extension | $1–$13 per linear foot | Homes with existing ductwork and central HVAC that can handle the additional load |
Sizing your AC correctly can help you keep costs low, but we also recommend using the Database of State Incentives for Renewables & Efficiency (DSIRE) to look for local rebates on attic cooling systems.
Ductless mini-splits cost more upfront, but they’re the most efficient solution for attic cooling, making them ideal for attics that see frequent or constant use.
What Affects the Cost of Cooling an Attic?
Several factors influence the cost of cooling an attic, including the space’s size and the quality of insulation.
Size of the Space
Homeowners and AC manufacturers measure a unit’s cooling capacity in British thermal units (BTUs). The larger the attic, the higher the required BTU rating. Higher BTU ratings typically increase costs. If you choose a smaller unit, the AC will struggle to cool a larger living space. If the unit is too large, you’ll waste energy, which will drive up your utility bills.
You generally need 20 to 35 BTUs per square foot of attic space, but you’ll also have to consider the ceiling height, insulation, roof’s sun exposure, and your climate. For example, you need a model with a higher BTU rating in a poorly insulated attic compared to a well-insulated one.
Finished attics must be at least 70 square feet, which would call for 1,400 to 2,450 BTUs, but most range from 100 to 160 square feet (2,000 to 5,600 BTUs). However, the smallest HVAC units you’ll find often start at 5,000 or 6,000 BTUs.
We also recommend looking at the Seasonal Energy Efficiency Ratio 2 (SEER2), which is the system’s cooling output divided by its power consumption during warmer months. The higher the SEER2 rating, the higher the system’s energy efficiency.
This BTU sizing chart can help you determine how powerful your HVAC unit needs to be with common finished-attic sizes:
| Size of Finished Attic (Sq. Ft.) | Recommended BTUs |
|---|---|
| 70 | 1,400–2,450 |
| 100 | 2,000–3,500 |
| 160 | 3,200–5,600 |
| 200 | 4,000–7,000 |
| 300 | 6,000–10,500 |
| 400 | 8,000–14,000 |
| 500 | 10,000–17,500 |
| 600 | 12,000–21,000 |
Attic Insulation and Ventilation
Poor attic insulation and ventilation increase cooling needs and energy costs throughout the entire home. Too little insulation allows heat to enter the space from the roof, raising the interior temperature. Without proper airflow, the space also traps heat. As a result, your main AC has to work harder to maintain a comfortable temperature.
While you can purchase a system with a higher BTU rating to make up for the lackluster insulation and airflow, you’ll only increase your utility bills. Instead, upgrade your insulation or add ventilation. We also recommend considering radiant barriers or attic fans, especially if the space doesn’t see frequent use.
Roofs absorb heat, but radiant barriers are highly reflective. Studies have found they reduce cooling costs by 5% to 10% in warm climates. Attic fans draw cooler air in, lowering energy costs and improving ventilation.
Installation Complexity
The more complex the installation, the higher the cost. In most cases, you don’t need an HVAC company to install window or portable units — you only need an existing window for venting.
However, ductless AC systems require HVAC professionals. You could see these extra installation costs on your bill:
- Installation: You’ll pay between $300 and $2,000 to mount and install a ductless unit, depending on the mounting location.
- Electrical work: If the attic doesn’t already have a 110- or 200-volt box, you’ll need an electrician for around $50 to $100 per hour.
- Refrigerant lines: Carpenters, who often charge between $25 and $50 per hour, cut holes for the refrigerant lines.
- Concrete pad: If you’re installing a brand-new AC unit, you’ll need a concrete pad for the outdoor condenser, which can cost hundreds of dollars.
Best Types of Air Conditioners for Attics
Ductless mini-splits, portable ACs, and window ACs are the top options for cooling attics.
Ductless Mini-Splits
For finished, frequently used attics, we recommend ductless mini-split systems. You can choose to install a single-zoned unit within the attic space or connect the attic to your whole-house mini-split. Either option allows you to control the attic’s climate independently from the rest of the house, enhancing the home’s overall energy efficiency.
Rosa highlighted several benefits of mini-splits over other options. “Window units block the view. Portable ACs take up floor space, and you need to have access to drain condensation,” he said. Since mini-splits are compact and hang on the wall, they won’t eat into your limited attic space or limit your window use. He added, “Ductless mini-splits double as heating systems, so you solve your heating and cooling needs.”
However, they’re much more expensive than portable or window AC units, and you’ll need space outside for the outdoor condenser. If you don’t use the attic regularly, the ductless mini-split system’s high upfront cost likely offsets most benefits.
Portable ACs
Portable air conditioners, also known as floor air conditioners, are compact units that can be easily moved from room to room as needed. They only require a vent — usually a window — so you won’t incur any extra installation costs.
While portable ACs are affordable, they typically only work well in temporary situations. They’re noisy, take up valuable attic space, and aren’t energy-efficient. Due to these factors, consider using a portable AC system if you only use the space occasionally, need a temporary solution, or require a unit that can be moved around the home as needed.
Window ACs
Window air conditioning units are another budget-friendly option. Typically DIY, they’re easy to install as long as you have the right window style and size. They work extremely well in small spaces.
However, window ACs aren’t as effective in large or poorly insulated attics. Additionally, many attics lack standardized windows. While you can install one through the wall instead, you need to talk to an HVAC technician to discuss structural concerns and building codes.
Tips To Cool Your Attic More Efficiently
Adding an AC unit to your attic will almost always result in higher energy bills, but you can make some improvements to increase the space’s energy efficiency.
- Add insulation. To prevent heat loss and exchange in the attic, use spray insulation foam or rigid foam boards. You can also add a radiant barrier to reflect heat away from your roof.
- Use window treatments or shades. In cooling season, 76% of the sunlight that hits standard windows becomes heat. Blackout window treatments and shades block incoming sunlight, reducing heat exchange. They’re especially helpful if your windows face the east or west.
- Install a ceiling fan. Ceiling fans don’t lower the attic’s temperature, but the air movement makes the room feel cooler. They improve air circulation, and when combined with an air conditioner, they distribute the cool air evenly.
- Seal air leaks. Air leaks around your attic doors and windows allow heat to escape in the winter or enter in the summer. Seal them to lower your AC’s energy load.
- Install a smart thermostat. Smart thermostats for mini-split units give you more control over the attic’s energy efficiency. You can pre-set the thermostat to match your routine, and some types will turn on if you enter the room (and turn off if you leave).
Next Steps
The cost of an attic air conditioner varies by unit type. Ductless mini-split units offer the best long-term performance, but they’re often the most expensive option. To choose the best type for your home, consider how frequently you use the attic and what you use it for. Then, measure the space, check the BTU requirements, and determine a budget. Compare the lifespans and warranties of the best systems. You can install a portable or window unit yourself, but if you decide to go with a mini-split, collect at least three quotes from qualified HVAC contractors.
In some cases, homeowners want to extend their central AC’s air ducts to the attic. However, as Rosa explained, “When you design a central AC, you design it for that space at the time of installation.” He added that unless you preplanned for that future finished space, your current forced air system can’t handle the additional, unexpected energy load. As a result, Rosa recommends going with a ductless mini-split to cool unusual or hard-to-condition spaces.
FAQs About Attic Air Conditioner Cost
What are the downsides of an attic air conditioner?
While installing an attic AC makes the space more comfortable and can keep overall energy costs down, downsides include easy-to-forget maintenance requirements, accessibility issues, and inefficient systems.
Since an attic AC unit is “out of sight,” it’s also “out of mind.” This can make it more difficult to determine when it needs maintenance, resulting in larger problems (and higher costs) down the road. You may also find it challenging to access your air conditioner for maintenance and repairs in smaller attics.
If your attic lacks proper insulation and has air leaks, you may be fighting a losing battle with your AC, driving up energy costs with minimal benefits. Upgrade any poor insulation and seal leaks before adding a cooling unit.
Can I extend my central HVAC system to the attic?
Yes, it’s possible to extend your central air conditioning system to your attic, if your existing system was designed with additional cooling space in mind. During the initial HVAC installation, you likely selected a system based on the size of your home and climate. If you didn’t originally account for a new finished attic, the existing unit won’t be able to efficiently or effectively handle the additional cooling load.
If your central air conditioner can handle the extra work, you’ll need to modify and extend your ductwork, which costs $1–$13 per linear foot. Replacing ductwork, specifically in attics, tends to cost between $2,200 and $5,600. You’ll pay about $2,500 more if you need to insulate your attic. Additionally, research local building codes regarding attic conversions and air conditioners, and ensure that your new ductwork is well-insulated.
Are window ACs effective in attics?
Yes, window air conditioners are effective in attic spaces. Compared to other cooling options, they’re less expensive upfront and require little space. You can expect to spend $150 to $550 on a window unit. You’ll generally spend more if you need a system with a higher BTU rating.
However, compared to ductless or central air, window units are less energy-efficient, especially in poorly insulated spaces. They also won’t work in every attic — they require a large enough window that can support the appliance.
Do attic fans help cool the space?
Yes, attic fans can help cool the room, reduce the load on your main HVAC system, and prevent damage to the home.
Poorly ventilated attics trap hot, humid air as it rises, which can damage the roof and any stored belongings, support mold and mildew growth, and cause ice dams in winter. The home’s AC then needs to work harder to cool the floor directly below the attic.
Attic fans circulate the air, removing hot air from the space and drawing in fresh, cooler air from outside. As a result, they prevent roof damage, improve the attic’s air quality, lower the overall temperature in your home, and reduce energy costs.
