Mr. Cool DIY 12K: Winter Heat Pump Power & Noise Test

The Mr. Cool DIY 12K mini-split heat pump has been a reliable unit in my attic room for over a year. I recently put it through a rigorous 24-hour winter test to measure its real-world power consumption and noise levels, even with outdoor temperatures dipping below freezing. The results revealed impressive efficiency and quiet operation.

What I Built

My setup for this test involved the Mr. Cool DIY 12,000 BTU 3rd generation mini-split heat pump, installed in a dedicated attic room. This room, approximately 17 feet wide by 17 feet long, features vaulted ceilings and is well-insulated with double-pane windows. The ceiling boasts about 8 inches of fiberglass insulation, while the walls have roughly 6 inches. The floor is also insulated, though there's unconditioned space directly below. To accurately measure the unit's power draw, I temporarily rewired the 120-volt unit to plug into a standard outlet, allowing me to use a Kill-A-Watt meter for precise readings.

Why It Works

The efficiency of this Mr. Cool unit, especially in heating mode, stems from its inverter technology. Unlike traditional HVAC systems that cycle on and off at full power, an inverter compressor can vary its speed to match the heating demand. This allows the unit to run continuously at lower, more efficient levels, preventing large temperature swings and reducing energy waste. The constant circulation of air by the indoor fan, even when the compressor isn't actively heating, helps maintain a consistent temperature throughout the room, eliminating cold spots. This continuous operation, combined with the excellent insulation of the attic space, contributes significantly to its low energy consumption even in harsh winter conditions.

Parts & Specs

To ensure accurate testing, I used the following components:

• Mr. Cool DIY 12,000 BTU Mini-Split Heat Pump (3rd Gen): The core unit under test, providing both heating and cooling.
• Kill-A-Watt Meter: Used to precisely measure the electrical consumption (watts and kilowatt-hours) of the unit.
• SPK2 Thermometer: Employed to monitor both indoor and outdoor ambient temperatures during the test period.
• Testing Environment: A well-insulated 17x17 ft attic room with vaulted ceilings and double-pane windows, featuring 8 inches of fiberglass insulation in the ceiling and 6 inches in the walls.

Math & Run-Time Numbers

The conditions during the 24-hour heat pump test were quite cold, with outdoor temperatures hovering around 30-31°F, well below freezing. Inside, I set the Mr. Cool unit's thermostat to 65°F. My independent thermometer, placed at table height, consistently read between 68-70°F, indicating the unit effectively maintained a comfortable temperature.

Here are the specific power consumption numbers I recorded:

• Unit OFF (Phantom Load): Even when the unit was turned off, it still drew a small amount of power, fluctuating between 16.8 and 18.8 watts. This "phantom load" is important to consider for overall energy costs.
• Indoor Fan ONLY (Idle Speed): With just the indoor fan running (not actively heating), the unit consumed approximately 20.1 to 20.8 watts. The fan never completely turns off, ensuring continuous air circulation.
• Full Heat Pump Mode (Max Speed): When actively heating at its highest capacity, the Mr. Cool unit pulled between 906 and 918 watts.

Over the entire 24-hour period, the total energy consumed by the Mr. Cool DIY 12K heat pump in heating mode was 7.30 kWh. Considering the freezing outdoor temperatures, this is a remarkably efficient performance.

Pros & Cons

Based on my year of ownership and this specific winter test, here's what stands out:

• Pros:
  • Extremely Quiet Operation: Both the indoor and outdoor units operate with very minimal noise, even when running at full capacity. The outdoor unit produces a gentle hum that's easily ignorable.
  • Excellent Efficiency: Consuming only 7.3 kWh over 24 hours to heat a well-insulated room in freezing temperatures is highly efficient.
  • Consistent Comfort: The unit effectively maintains the desired indoor temperature without significant fluctuations.
  • DIY Friendly: The "DIY" aspect of the Mr. Cool line means it's designed for easier homeowner installation, saving on labor costs.
• Cons:
  • Phantom Load: The unit draws a continuous ~17-18 watts even when turned off, which adds up over time.
  • Continuous Fan: While good for air circulation, the indoor fan never truly turns off, contributing to the idle power draw.

When To Use This vs. Alternatives

The Mr. Cool DIY 12K mini-split is an excellent choice for anyone looking to efficiently heat a single zone in their home, such as a finished attic, a detached garage, or a workshop. Its quiet operation is a huge benefit for living spaces, and its efficiency in cold weather makes it a strong contender against electric resistance heaters or less efficient window units. If you have a larger home or require multi-zone heating, you might consider multiple mini-split units or a more complex central heating system. However, for targeted, cost-effective heating in a smaller, well-insulated area, this unit is hard to beat, especially if you're comfortable with a DIY installation to save on costs.

Bottom Line

After putting the Mr. Cool DIY 12K mini-split heat pump through its paces in genuine winter conditions, my positive experience with the unit only strengthened. It delivers on its promise of efficient and quiet heating, even when battling freezing outdoor temperatures. For homeowners seeking an effective, easy-to-install, and energy-conscious heating solution for a specific area, this unit is definitely worth the investment.

Final Wrap-Up

I hope this detailed breakdown of the Mr. Cool DIY 12K’s winter performance was insightful for you. Be sure to subscribe to the YouTube channel for more hands-on tests and reviews, including an upcoming summer cooling consumption report for this very unit! If you have any questions, drop them in the comments below, or explore my gear page for other recommended products.