Mistbox wants to help you save 30% on your AC bill

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I don’t know where you live, but here in Southern Indiana, electricity bills this time of year tend to soar due to heavy use of air conditioner units. Keeping your home cool is a must when humidity levels are high and temps are in the 90’s. How can you optimize your AC unit to save money on your monthly power bill? Keeping doors and windows shut and your blinds closed during the day can help a little. But Mistbox is a gadget that connects to your outdoor AC unit and could save you up to 30% on your monthly bill. Mistbox consists of a water pump and four sprayer arms that attach to the sides of the AC unit to spray a fine mist of cold water when the AC unit is running. The water mist cools the surrounding air around the AC unit, making it easier and faster to cool your home. Sound like snake oil? I hope to fine out. They have sent me one to try. I set it up yesterday, so I’ll have a review in a few weeks. The unit is priced at $399 from mistbox.com or Amazon.

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12 thoughts on “Mistbox wants to help you save 30% on your AC bill”

  1. Gadgeteer Comment Policy - Please read before commenting
    1. There’s a water saver mode. According to the info included with the Mistbox, it only uses pennies a day. I’m not sure how to measure the amount of water used. It would depend on how often the AC unit runs and for how long. So usage would be different for each installation and would vary daily.

  2. Meter away Julie


    I can’t vouch for this misting product, but I can vouch for the process itself. Our first house had Central air that was barely capable of cooling our house on normal days. When the temperature exceeded 100+ (110,115,yuck) the AC struggled to keep the house under 89 running 24/7. We would wrap a mister around our poor abused AC unit, allowing us to knock another 10 degrees off. Eventually we found the funds to replace (30 year old single pane) windows, and insulation which helped the most allowing us to bring the house down to 75 and not need the AC running 24/7. The AC eventually died (also 30 years old) and we replaced it with a over sized unit which our renters are now appreciating.

    We are now back into a similar situation with our current house. The AC is in much better shape, but when it hits 105+ it’s just hard to keep up. I once again setup misters July 3-4th for our sons Birthday party and Independence day. With 30+ people in the house all day and 10 kids running inside and out we took every advantage we could to gain an edge on the heat.

    Drawbacks: If you live in a hard water area, you will need to periodically spray your coils and fins down with de-scaller or the buildup will counter any improvement you get from the reduced evaporation effect of the mist.

  3. Sounds like a lot of variables in the equation, and you have no control against which to compare your results …

    1. Depending on how much she wants to get into testing, She can compare relatively.

      If she has a smart AC control. Pick two days with similar conditions, set internal temperature the same. Monitor the Cycle times of the compressor.

      If you really wanna get into testing, slap a energy meter on the circuit for the AC. Monitor the draw while on and off over a period of 24/48 hours. The compressor is the most energy hungry part of the system. The mist will reduce the frequency and duration the compressor is running. This can be measured.

      1. I don’t have an energy monitor but my Venstar thermostat does keep track of how much time the AC was on daily and weekly. I know that’s not overly detailed/scientific, but hopefully I can get an idea by comparing days with the same temperature using and not using the Mistbox.

  4. This device is a variant of what we in the state of Nevada call a swamp cooler. They were used routinely before home air conditioning and are based on the fact that as water evaporates, it takes heat out of the surrounding air. Many homes in Nevada in the 1920’s had these systems. We use a similar device called a misting system on our patio to cool us off. The problem is that it requires a low humidity environment to work well. During the summer, the humidity in Nevada is 10 – 15% so you do get significant cooling. If the humidity is high, the water will not evaporate so the cooling will be minimal. The system may work but probably but as well as you hope.

    1. These systems don’t actually work by cooling the air around your coils or intake. The mist attaches to the fins/coils on your AC condenser energy (heat) is then transferred into the water via the coils evaporating the water. The wet coils/fins transfer the heat out of the compressor system quicker and more efficiently than air alone. The result is the coolant returning to your AC system returns with a lower energy level (temperature) in a shorter time. Your compressor does not have to work as long or hard to reduce the energy (temperature) of the coolant. Greatly simplified mist reduces the energy (electricity) required to dissipate the heat, and increases the efficiently of removing the heat from the system. Even High Humidity places will see an improvement from this system. But you are right about “swamp” coolers. Once the humidity increases to a certain point it begins to feel like you are sitting in a…well swamp.

      1. But if the humidity is high, the coils won’t evaporate the water. Still might be helpful though. (Heat transfer to water is likely to be faster than to air. The only problem is if you end up with hot water on the fins that won’t evaporate, but most fins I’ve seen are vertical, so it should just run off.)

      2. As an engineer I would like to define the use of mist.
        The water needs energy to phase change (like boiling for instance, you need to increase the temperature to make it steam, you need to give energy)
        as the water evaporates it takes the energy needed for the phase change from the surroundings, which is the fins of the AC unit as they are the easiest and fastest source. As the water evaporates it takes the energy which the AC unit is struggling to transfer to air. The water will evaporate because there is a fan blowing. This is true of course as long as the mist is not too much. The mistbox system will determine the volume of mist produced in order to not overcome the evaporation process and reduce effectiveness.
        This mist evaporation from the fins will surely increase the cooling of the gas inside the AC unit improving not only the cooling but lowering the bill as well.

  5. We had a duplex in the D/FW area and the landlord wouldn’t replace the old clunker a/c compressor. During the summers we couldn’t use the oven because it put to much of a heat load on the house. The a/c compressor would run 20 hours a day and would only shutoff around two o’clock in the morning.

    I took a bunch of 1/2 inch PVC pipe and put four Arizona Misters on each side of the compressor and I could tell a difference. Did it solve all of our problems, no. But it did give us an edge on the Texas heat.

    In an urban environment the water will mix with the rest of the crud in the air and it will form a nasty mix on the compressor coils by the end of the summer. You are also bathing your $2000 compressor in a constant bath of water so expect increased corrosion.

    Your best bet in the long run is to replace your old AC with an increased SEER unit, increase your insulation, seal up your house and not use the misters. It will take you three or four years to regain the investment but you’ll be much happier in the long run.

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