Build Your Own Walk In Cooler with a CoolBot Controller and A/C Unit

A CoolBot and household window A/C unit lets you turn any well insulated room into a walk in cooler, saving you thousands versus a commercial cooler.

You can build your own walk in cooler for produce storage at just a fraction of the cost of commercial coolers. A CoolBot and a regular household window A/C unit lets you turn any well insulated room into a walk-in cooler. Instead of paying over $5000 for a small commercial walk in cooler, you can save thousands with this DIY cooler option.

What’s a Coolbot?

A CoolBot it a small (roughly hand sized) controller that allows you to use a standard window AC to produce temps in the upper 30s (F). From the CoolBot website:

The CoolBot uses multiple sensors, a heating element and a programmed micro-controller to direct your air conditioner’s compressor to operate in a such a way to cool the room to 36° F without ever freezing up. Additionally, our innovative interface which links the CoolBot controller to your air conditioner allows for 5 minute installations without any training, cutting, soldering or even taping.

CoolBot walk in coolers are perfect for: hunters, farmers, cheese makers, homesteaders, brewers, preppers, dairies, taxidermy, or those who want additional food storage.

A CoolBot and household window A/C unit lets you turn any well insulated room into a walk in cooler, saving you thousands versus a commercial cooler.

Why Build a Walk In Cooler?

I run a produce delivery service and was struggling to hold my produce. We quickly ran out of space in our traditional refrigerators, and I had a hard time controlling the temperature. Some produce would freeze and some would spoil quickly due to temperature irregularities. I was losing hundreds of dollars in inventory weekly.

A friend of mine that is a farmer and owns a local nursery recommended a product called a CoolBot. Her husband turned their storage shed into a walk-in cooler by adding a Coolbot to their window unit and double insulating the walls. After some research, we decided to add a cooler to a room in our garage.

Which Insulation is Best for a Walk In Cooler?

Standard fiberglass insulation

Fiberglass insulation proved to be the least initial expense. You would need to double it to create the recommended R-25 value (like my friend did). The down side is condensation buildup. You’ll need to replace the insulation every five years or so, because it will get wet and mold over time. If you need a walk in cooler for 5 years or less, this would be the cheapest option.

Blown Insulation and Foam Insulation

Blown and Foam insulation is easy to install and works well with existing rooms. Unfortunately, it doesn’t provide the needed R-Value (25 or greater), and is susceptible to the same condensation and mold buildup as fiberglass insulation.


Polystyrene is the best insulation to use for cooler applications. It’s what they use for commercial coolers. The down side it is hard to find and not cost effective to ship.

After much research and pricing all the options, we decided to look into used walk-in coolers. Much to our surprise, we were easily able to find a local (within a 2 hour drive) contractor that removed equipment from restaurants and grocery stores and had used walk-in coolers for sale. We bought an 8×9 Walk-In Cooler that included all the side panels, ceiling, and enough extra panels to make a door, all for $300.00.

We decided to use a room inside of our garage that hubby graciously gave up for us to install our cooler. This location was perfect because:

  • it had a concrete floor (best recommended flooring)
  • there was a power source
  • the a/c unit would be protected from elements and out of the sun
  • the garage would add to the efficiency and longevity to the cooler

Because we did have to prefab a lot of the interlocking panels to fit our space, custom build and modify a door, and run electricity to the cooler, I would give this DIY project a 4 out of 5 for carpentry skill level. If you converted an existing shed or room with electricity into a cooler using insulation and sheathing, then moderate carpentry skills could easily accomplish this project.

A CoolBot and household window A/C unit lets you turn any well insulated room into a walk in cooler, saving you thousands versus a commercial cooler.

Which AC Unit Should I Use with a CoolBot?

After building the rest of the walk in cooler, we added our window unit. The size of A/C you need will depend on the size of your room.

Size of Air-Conditioner => Dimensions of the Walk-In Cooler

  • 10,000 BTU = 6′ x 8′ x 8′
  • 12,000 BTU = 8′ x 8′ x 8′
  • 15,000 BTU = 8′ x 10′ x 8′
  • 18,000 BTU = 8′ x 12′ x 8′
  • 24,000 BTU = 10′ x 14′ x 8′

You have to have an A/C Model with a digital display, because the Coolbot will not function properly without this feature. See “CoolBot AC Unit Size and Brand Recommendations” for more information.

Once you have your room or cooler well insulated and your window A/C in place you can install your CoolBot to create your walk in cooler.

How to Connect Your AC Unit and CoolBot for Your Walk In Cooler

Installing a CoolBot with your Window A/C (from

  1. Install any brand of window A/C unit which you’ve purchased separately. (See our A/C Selection Guide to make sure you have the right air conditioner for your space). Cut an appropriate-sized hole in the wall of your walk-in cooler, put the A/C unit into the hole, and then use some type of insulation, like foam sleeves for pipes, so that you can easily remove the A/C instead of having to carve it out in case you switch A/Cs in the future.
  2. Plug the CoolBot into a standard outlet – the CoolBot uses no more electricity than a cell-phone charger, so no special electrical connections are needed.
  3. There are three labeled wires coming out of the CoolBot:
  • The first (labeled “Room”) measures the temperature of the room. Let it hang free, but make sure it is not making contact with any metal and not in the direct pathway of the cold air coming from the A/C.
  • The second wire (labeled “FIN Sensor”) is placed into the front cooling fins of the A/C unit. Gently place the sensor as low as possible, but ABOVE the first horizontal cooling tube. Use a pen or pencil to widen a space 1-2 inches up from the bottom and put the fin sensor 1/3 of an inch in so it is not touching the coolant pipes behind them. It should stay there on its own. No tape or screws. You may need to gently pinch the fins closed around the sensor, but be careful not to damage the sensor.
  • The third wire (labeled “Heater”) attaches to the A/C’s temperature sensor. The temperature sensor actually comes out of the A/C; on a new A/C the temperature sensor will be mounted on small plastic brackets in front of the fins. Wrap the CoolBot “Heater” wire up with that air-conditioner temperature sensor using a small 1/2 inch by 1 inch piece of aluminum foil (included) to ensure a good thermal connection. Allow this foil pack to hang freely away from any metal and out of the direct pathway of cold air.
  1. The CoolBot comes pre-programmed to cool your room down to 42°F (5.6°C), however, you can set it to whatever temperature you want.

Does the CoolBot Cooler Work?

Almost one year after installation, and I can’t say enough about this product. It allowed me to expand our CSA business, increased our food storage capabilities, and – as an unexpected bonus – our walk-in cooler doubled as a shelter during a hurricane.

We recently went through Hurricane Matthew here on the coast of South Carolina and we were not able to evacuate in time. Our family took shelter in our cooler as the eye of the storm and heaviest winds passed over us. With the reinforced walls, concrete foundation and sound structure, it was the perfect safe haven for us to weather out the storm.

A CoolBot and household window A/C unit lets you turn any well insulated room into a walk in cooler, saving you thousands versus a commercial cooler.

How Much Does a CoolBot Walk In Cooler Cost?

The cost of your walk in Cooler will vary greatly depending on many factors, such as:

  • Using an existing room or building new
  • Size of the room
  • Materials – flooring, insulation, A/C unit, CoolBot
  • Hiring a contractor or building it yourself

You can lower costs by watching for sales and buying seasonally. (Wood cost changes weekly, A/C are more expensive in summer than in winter and so on.)

Even with all of these factors in play, you can still build your own walk in cooler for a fraction of the cost of buying a commercial cooler by using a CoolBot. Our costs were as follows:

  • CoolBot – $330.00
  • Cooler Insulation and framing – $300.00
  • A/C Unit (we already had one to use) – $0
  • Electrical Supplies (wire, conduit, breaker, light) – $50.00

Total Cost $680.00

The CoolBot uses 40% less electricity than traditional coolers, which saves us hundreds of dollars per year. The cooler has also saved us thousands of dollars by preventing produce spoilage.

In northern climates you may be able to keep food cool in a root cellar, but for southerners and those who need to maintain a set temperature range (like commercial kitchens), a walk in cooler is a must for large scale cool storage.

Have you tried using a CoolBot or walk in cooler? Share your experience.

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A CoolBot and household window A/C unit lets you turn any well insulated room into a walk in cooler, saving you thousands versus a commercial cooler.

Amber BradshawThis is a guest post by Amber Bradshaw of The Coastal Homestead. Amber is a environmentalist, homesteader, garden and outdoor enthusiast. She is a wife, mother of three. Amber owns a contracting business with her husband, was President of the local Herb Society for the last three years, a 4-H Leader, Blogger and runs a CSA. Amber strives to get back into nature with a more sustainable and self-reliant lifestyle that fits a busy schedule and a tight budget. She lives on the east coast with her family on a little over 1/4 acre and encourages others to do big things with small spaces.

When not out in the garden you can find her sharing her latest homestead tips at The Coastal Homestead, on Facebook, on Pinterest or Instagram.

Posts may contain affiliate links, which allow me to earn a commission to support the site at no extra cost to you. Thank you!

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