Midwest summers are a hot, sticky affair, and my old house was never outfitted with an HVAC system. So, I have to rely on window and portable air conditioners to cool this 4,000-square-foot space. Over the last seven years, I've tested 34 of the best air conditioners, and the Midea Duo Smart Inverter Portable Air Conditioner tops all of the portable units on my list.

The Midea Duo fits my bedroom's sliding window, which won't accommodate window units. It runs quietly keeping me undisturbed at night, features an intuitive app, and does an outstanding job cooling, earning it the top spot in our best portable air conditioners guide.

The Midea Duo has two design features you don't find in most portable air conditioners. First, it has an inverter compressor. Instead of turning on and off, an inverter compressor has a variable-speed motor that slightly adjusts to keep your room at its target temperature. Inverter compressors tend to be more efficient than traditional motors.

Whereas most portable air conditioners just have one hose for exhaust, the Midea Duo has a unique hose-in-hose design. While it looks like there's just one large hose, the Midea actually has two hoses in one, so it can expel hot air while drawing in more air to equalize the room's pressure. This keeps hot outside air from seeping in to equalize the pressure.

Installing the Midea portable air conditioner was easy and didn't require any tools, but I hit a few snags along the way. I had the unit running within half an hour of opening the box, five minutes of which were spent installing and connecting to the Midea Air app.

To set up the AC, assemble and install the window slider and attach the hose. However, this is easier said than done. The slider is loosely held at your custom length with plastic pins. If you need to move or adjust the slider, the setup falls apart, and you must reassemble it. 

Attaching the hose is a breeze if you have a hung window, but I have a slider window, which requires using the included attachment. The pieces don't fit perfectly, so you must get it just right to keep the hose attached.

Once installed, the Midea comes with foam seals, insulation for improved efficiency, and a security bracket to keep intruders from entering.

I test all portable air conditioners in the same 550-square-foot room. I run them on high for two hours and compare before-and-after temperature readings to see how well they cool the room. The Midea Duo reduced the temperature by 3.3 degrees Fahrenheit in two hours, one of the best performances I've seen.

I have used the Midea Duo in my bedroom for two years. Since I often just want to decrease the humidity in my house, I mainly use the Midea in dehumidifier mode. This was enough to keep my room comfortable most nights. I switched to AC mode when I was going through a heat wave. If you live in a particularly humid region, using the Midea Duo as a dehumidifier is an excellent option.

If you want your bedroom as quiet as possible, this is the portable AC to get. On low, the Midea Duo was 43 decibels, a little louder than ambient noise and five decibels quieter than any other unit I've tested. I got my readings using a decibel meter positioned 6 feet from the AC. It was still only 56 decibels on high, quieter than a normal conversation.

I live on a busy city street where having a loud vehicle is a status symbol. So, at times, I almost wish the Midea's white noise was louder to drown out the "performance" mufflers and rib cage-rattling woofers.

To me, there are two key aspects to any "smart" device: features and reliability. I'd argue reliability is more important than flashy features. What's the point of having all the latest features if the AC never stays connected to your phone?

This wasn't a problem with the Midea Duo. I never had issues connecting to or using features. I have little patience for malfunctioning apps; the Midea app was a breath of fresh air. I live in an Alexa home, and the Midea paired with it for voice control. It also works with Google Assistant.

The app is user-friendly and full of features. Want to turn off the LED lights while sleeping? Press the LED button. Don't want the buttons to beep when you press them? Mute them with the Sound button. Then there are your standard scheduling, mode adjustments (fan, dehumidify, cool, auto), and fan speed functions. I used the scheduling function to turn off the Midea during the hours my utility company charged more for electricity.

The app also indicates when to clean the filter, which you should do every two weeks. Vacuum or wash the filter with water and allow it to dry completely before reinstalling it.

The main maintenance task you should stay on top of is cleaning the air filter every two weeks. To access the filter, you remove the grill on the back of the unit. I use a handheld vacuum to clean it, but for a more thorough cleaning, you can use water, just make sure the filter dries completely before you reinstall it.

You should also drain the water collection tray whenever the portable AC shows a "P1" error and before you store it for the season. I found minimal water collected.

If you have shedding people or pets in your home, wipe down the grill periodically to keep it clear of hair for better airflow. And, if you really like cleaning, wipe the entire unit down with a soft cloth occasionally.

While the inverter compressor is supposed to be more efficient, my smart plug told a different tale. It was the biggest energy user I tested, using 2.1 kWh during the two hour test period. Over a summer, that will cost you $124 on average if you run the AC on high for eight hours daily. 

Despite their name, portable air conditioners aren't all that portable. This is especially true with the Midea Duo. At 75 pounds, it's a pain to move from one floor to another, even if it does have handles. I uninstalled and reinstalled it in a different room on the same floor in about two minutes, but it was slower than most portable ACs because of how loosely the window slider is held together.

The sliding window attachment doesn't keep the hose attached to the window slider, which is crucial if you want to cool your room. I had to resort to duct tape to keep it in place. If you have a hung window, there's no need for the sliding window attachment. 

The Midea Duo is similar to the LG LP1419IVSM Smart Wi-Fi Portable Air Conditioner, the former top pick in our guide to the best portable air conditioners. They both have inverter compressors, are close in price, and have useful apps. The Midea Duo did a little better job of cooling, ran quieter, and is consistently in stock. However, the LG is much more energy-efficient. If you want to save on energy costs, choose the LG. Read our full LG portable air conditioner review.

If your window can accommodate a window air conditioner, get a window air conditioner. Window ACs are better at cooling, cost less, and are more energy efficient. A Midea model tops our best air conditioner guide. If you need more convincing, I compare portable air conditioners vs. window air conditioners. Also, check out our Midea U-Shaped Air Conditioner review.

Though it uses a lot of electricity, the Midea Duo Smart Inverter Portable Air Conditioner works well. It's among the best at cooling, operates quietly, can handle larger spaces, and has a unique hose-in-hose design that keeps warm air from rushing back into the room. Plus, the app is packed with features that work reliably. If you want a powerful yet quiet smart portable AC, this is the one to get.