Updated: February 24, 2026
When Spokane’s winter sets in — keeping your home warm efficiently becomes more than a convenience — it’s a necessity.
If you’re using a ductless mini split system, you already have one of the most energy-efficient heating options available. But how do mini splits work in cold weather, and what can you do to help yours perform at its best when temperatures dip below freezing?
At Mainstream Electric, Heating, Cooling & Plumbing, we’ve spent over 20 years helping Spokane homeowners stay warm through the Inland Northwest’s toughest winters. Here’s how you can make your cold weather mini split system run efficiently all season long—saving energy, extending its life, and keeping your home comfortable no matter what’s happening outside.
How Do Mini Splits Work in Cold Weather?
Modern cold-climate mini splits are built to perform remarkably well in freezing temperatures. Unlike older heat pumps, today’s systems use advanced inverter technology to adjust their output as the temperature drops, efficiently pulling heat from the air—even when it’s below zero.
Many of the best mini splits for cold climates can continue heating at temperatures as low as -15°F, making them well-suited for Spokane’s winter lows. As the outdoor temperature falls, the system’s compressor works a bit harder, but it still provides steady, reliable heat throughout your home without the unevenness of traditional furnaces or baseboard heaters.
So yes, you can confidently run your mini split all winter in the Inland Northwest. The key is knowing how to set and maintain it properly for the most efficient performance.
The Most Efficient Way to Run a Mini Split in Winter
Set It and Forget It
One of the most efficient ways to run a mini split in winter is to maintain a steady temperature. Constantly adjusting your thermostat can make the system work harder and use more energy. Instead, pick a comfortable temperature and keep it consistent—around 68°F to 72°F during the day and a few degrees cooler at night.
If your system has multiple indoor units, set each zone according to how often you use the space. This steady approach helps your mini split run smoothly and efficiently, minimizing wear on the system.
Use ‘AUTO’ Mode and Inverter Technology
Your mini split is smarter than you might think. The AUTO mode automatically adjusts fan speed and compressor output to maintain your chosen temperature without wasting energy. With inverter technology, the compressor ramps up or down instead of turning fully on and off—much like cruise control in your car—saving energy and preventing sudden temperature swings.
If your mini split is older or not rated for cold-climate performance, it may not heat as effectively during extreme cold. Modern cold-climate ductless heat pumps are designed specifically for subzero operation.
Tip: Mainstream offers flexible financing to make upgrading your HVAC easy—ask about current promotions for new mini split installations.
Why Your Mini Split May Struggle in Cold Weather
Even high-quality cold-climate mini splits can experience performance issues during Spokane’s coldest stretches. If your mini split is not heating in cold weather or seems to be blowing cold air in winter, these are the most common reasons.
The Outdoor Unit Is Working Overtime
Mini splits pull heat from the outdoor air and transfer it indoors. When temperatures drop below freezing, there’s simply less available heat to extract.
That doesn’t mean the system is broken — but it does mean the compressor has to work harder. As outdoor temperatures fall into the teens or single digits, you may notice slightly reduced output. This is a normal part of how heat pumps operate in extreme cold.
Ice or Frost Buildup on the Coils
During snowy Spokane winters, frost can accumulate on the outdoor coils. When airflow is restricted by ice, the system cannot absorb enough heat to warm your home efficiently.
Most modern mini splits automatically enter a defrost cycle to melt buildup. However, if ice continues forming or the unit stays frozen, it may signal airflow restrictions, drainage problems, or a maintenance issue.
Dirty Filters or Indoor Coils
Dust, pet dander, pollen, and even wildfire smoke common to the Inland Northwest can collect inside filters and coils. Over time, this buildup restricts airflow and reduces efficiency.
If your mini split feels like it’s blowing lukewarm air, clogged filters are often the culprit. Cleaning them monthly during peak winter use makes a noticeable difference.
Low Refrigerant Levels
If your mini split is blowing cold air while set to heat mode, low refrigerant may be the issue. Refrigerant is essential for heat transfer. Even a small leak can significantly reduce heating performance and should be addressed by a licensed technician.
Incorrect Settings
Before assuming something is wrong, double-check the basics:
- Make sure the system is set to “HEAT” mode, not “COOL” or “FAN.”
- Confirm the temperature is set high enough to trigger operation.
Sometimes the solution is simpler than it seems.
Protect and Maintain Your Outdoor Unit
While your ductless mini split’s indoor unit keeps you comfortable, it’s essential not to neglect the outdoor component. The outdoor unit plays a crucial role in your system’s performance, and it’s exposed to the harsh winter elements. To ensure your mini split operates at peak efficiency throughout the season, take these steps to protect and maintain your outdoor unit:
- Keep at least 12–24 inches of clearance around the unit for proper airflow.
- Gently remove snow buildup after storms, but never chip away ice with sharp tools.
- Make sure the unit’s base allows proper drainage so melted frost does not refreeze underneath so melted frost does not refreeze underneath and restrict airflow.
Elevate or Shelter the Outdoor Unit
The placement of your outdoor unit can significantly impact its performance in winter. When installing the unit, make sure it is positioned above the expected snowfall levels in your area. This will prevent snow from being drawn into the system, which can hinder its ability to function properly. If possible, consider installing the outdoor unit under an overhang or roof to provide additional protection from snow and ice accumulation. Alternatively, you can use a weatherproof cover specifically designed for your mini split’s outdoor unit to shield it from the elements when not in use.
Utilize the Defrost Mode
Frost buildup on coils is a common issue during winter, as the cold air can cause condensation to freeze. If left unchecked, this frost can impede the system’s ability to transfer heat effectively, leading to reduced efficiency and potential damage. Fortunately, most modern ductless mini splits come equipped with a defrost mode designed to combat this problem. When activated, the defrost function temporarily reverses the heat pump’s operation, allowing it to melt away any frost or ice on the coils. This ensures your system can maintain optimal performance even in freezing conditions. To get the most out of this feature, make sure the defrost mode is enabled on your outdoor unit during the winter months.
By taking these proactive measures to protect and maintain your outdoor unit, you can help your ductless mini split brave the winter weather and continue to provide efficient, reliable heating for your home. Regular attention to your outdoor unit, combined with the optimization of your indoor settings, will ensure your mini split remains a valuable asset in your home comfort arsenal for years to come.
Best Temperature Settings for Ductless Mini Splits in Winter
For Spokane-area homeowners, where daytime highs can hover in the 30s or 40s and nights often dip below freezing, the best temperature settings for ductless mini splits in winter balance comfort and efficiency:
- Daytime: 68°F–72°F
- Nighttime: 64°F–68°F
- When away: Lower only 3–5 degrees—too much of a drop forces your system to work harder to reheat the space
Avoid switching your mini split off completely when you’re away. Keeping it running at a steady, lower setting prevents the indoor coils from cooling too much, allowing it to reheat efficiently when you return.
Why Mini Split Maintenance Matters in Spokane
Spokane’s climate puts unique demands on heating systems. Winter snow, freezing overnight lows, and seasonal temperature swings all affect mini split performance.
Because ductless systems run year-round for both heating and cooling, components experience ongoing wear. Dust from dry summers, pollen, and wildfire smoke settle into filters and coils. Winter moisture from repeated defrost cycles can also strain drainage components if they aren’t inspected regularly.
Without routine maintenance, even a high-quality mini split can struggle during peak winter demand.
Clean Filters and Coils Regularly: Dirty filters restrict airflow and make your system work harder. Check and clean filters once a month during peak winter use.
Schedule Professional Check-Ups: Even with great DIY care, your mini split benefits from professional attention. Mainstream’s licensed HVAC technicians inspect electrical components, check refrigerant, and test performance under load to ensure your system is winter-ready.
As part of our Care Club, Spokane homeowners enjoy:
- Priority service during peak season
- Two precision tune-ups per year
- Discounts on parts and repairs
- 100% satisfaction guarantee
A well-maintained system performs better, lasts longer, and saves you money—so you can focus on enjoying your winter, not worrying about your heater.
Know When to Use a Backup Heat Source
Most modern cold weather mini splits can handle Spokane’s winters with ease. But when extreme cold snaps push temperatures below their optimal range—around -10°F or lower—it’s smart to have a backup heat source for peace of mind.
Supplementary Heat for Extreme Cold
In those rare deep freezes, a secondary heat source like a furnace or small electric space heater can help maintain comfort. Because electrical demand rises when extra heaters are in use, your home’s electrical system plays a critical role in keeping everything running safely.
That’s where Mainstream’s expertise makes a difference. As Spokane’s trusted team for heating, cooling, and electrical, we look at your home as a whole—ensuring your electrical panel and circuits can safely support your heating systems. Our licensed electricians and HVAC technicians work together to optimize performance and protect your equipment, keeping your home warm, safe, and efficient even in the coldest conditions.
Mainstream Is Here to Keep Spokane Warm
At Mainstream Electric, Heating, Cooling & Plumbing, we’re not just a service company, we’re your neighbors. For over two decades, we’ve helped families across Spokane and Northern Idaho stay comfortable year-round with honest work, fair prices, and community-first service.
Whether you’re exploring the best mini splits for cold climates, need help with a mini split not heating in cold weather, or just want advice on the most efficient way to run your mini split in winter, our team is ready to help.
We offer 24/7 emergency HVAC service, financing options, and our Care Club maintenance program, all backed by Mainstream’s 100% Satisfaction Guarantee—because we treat your home like our own.
If Spokane’s cold weather has you wondering how your mini split will hold up, give us a call or schedule online today. We’ll make sure your system is running efficiently, safely, and ready for every chilly morning ahead.
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