Build Your Own Solar Evaporative Cooler - Survival-training.info

Build Your Own Solar Evaporative Cooler 

By: Jim Eddy - Susanville, California 

I live in an all solar house in Northern California. It is a passive design so 

the sun heats it by shining in the windows. I solar heat our water and have a 1 

kilowatt solar electric charging system providing 110 volts of AC power. The one 

thing I could not do was cool the house easily in the summer without taxing the 

system. I purchased an evaporative type unit for indoors but it did not do much 

good. A compressor type air conditioner would use more energy than I could 

supply and a regular evaporative cooler would use a lot of energy. I figured that 

some sort of solar cooler could do the trick. 

I spent sometime looking for a solar evaporative cooler on the Internet. 

Those that I found were bulky, ugly and expensive. Most cost around $ 600.00 and 

up. The above pictures are of a Solar evaporative cooler that I made using easily 

purchased components to cool our 1600 square foot house. I spent roughly $300 to 

make this unit. It is in it’s fourth year of use. If you have some of the components 

already you could spend much less. The cost of a new solar panel to power the unit 

is around $550 and can be purchased at many local or on line stores. 

Afternoon Summer temperatures range between 85° to 95° in this part of 

California. The cooler that I purchased is smaller than I should have for my house 

size, but it does a good job of keeping the house cool. With the fan and pump 

modifications, it maintains a temperature difference of about 15° between the 

outside and the inside. As I am writing this it is 4:30 in the afternoon. The outside 

temperature is 92° and the inside temperature is 77°. Anyone with an existing 

evaporative cooler of any size can make a similar looking cooler, or you can buy 

one like I did. 

1 www.livingonsolar.com

I decided to use an existing evaporative cooler because I didn’t want to reinvent 

the wheel. All the components are already there, the cooler pads, a trough to 

hold water, a float valve to let more water in and a water distribution system. As 

you can see from the pictures I 

mounted a 12 volt radiator fan in front 

of the existing opening and I opted to 

leave the existing AC pump, motor and 

squirrel cage intact. Since I have 110 

Volt AC power available at my house, 

on occasions, I use the existing AC 

pump and motor after the sun has gone 

down to continue cooling the house. I 

was concerned that leaving everything 

there might significantly block the 

airflow, but it seems to work just fine. 

You could remove the existing motor 

and pump and It might work even 

better. If you do use the AC fan, make 

sure the 12 Volt fan does not turn as it 

could cause it to burn out. I use a coat 

hanger inserted through the front and 

placed between the 12 Volt fan blades 

and it’s housing. It seems a little hoaky 

but it keeps the fan from turning. 

I purchased the electric radiator fan at a local auto parts store. I paid around 

$80 for it and have seen similar fans on the Internet for $35. The pump is a 12 volt 

bilge pump that I purchased at Wal Mart for around $14. Make sure that you don’t 

use too strong of a pump or you will blast the water into the feeder tubes. 

At full speed the fan pulls 5.5amps @ 12 volts. The bilge pump pulls around 

1.5 amps @ 12 volts. A 100 watt solar panel will power the fan and pump nicely. I 

am using a Mitsubishi 110 Watt panel that is mounted on a solar tracker that I 

made. The panel and tracker are mounted on the ground in front of the cooler. In 

previous years I have placed the panel flat on the roof just above the cooler. That 

worked fine for most of the day. The tracker extends the time in the afternoon 

when the summer temperatures are keeping things hot. 

You can decide for yourself how you want to mount the fan. I drilled holes in 

the sheet metal and used sheet metal screws to attach it. I did have to do some 

cutting of the sheet metal with a Dremel tool to make it fit. Radiator fans can be 


hooked up two ways electrically so the fan can blow air in either direction. Make 

sure you hook it up correctly to blow the direction you want. 

I removed the existing front cover to expose the opening. I then placed the fan over 

the opening to determine the best fit and drilled holes in the sheet metal. 

I opted to leave the cover in tact as much as possible so I had to fit the fan back 

into the cover before mounting everything to the main housing. It was a tight fit! 

After sliding the fan into the cover, I mounted both onto the main housing with the 

existing sheet metal screws and 4 new ones for the fan. 


The bilge pump can be placed in the water right alongside of the existing AC 

pump. You can disconnect the hose from the existing pump and place it on the 

bilge pump. You may have to use additional hose and an adapter like I did. 

I mounted two new rocker switches to the front of the existing cover on the side 

opposite of the existing switches. I was able to drill holes in the plastic and they 

mounted nicely. 

The finished front installed inside. 

The panel and tracker that I use. 


Wiring the solar panel to the fan and pump is relatively easy if you have 

some experience. Solar panels have different types of connectors depending on 

which kind that you have. Some have junction boxes that allow wire to be placed 

into the box and a secure connection made. Newer panels have MC connectors 

which allow for a snap fit for multiple panel connections. These would probably 

have to be cut to connect the wire. The better way to do this is to buy an MC 

extension which has both male and female ends on it. It can be cut in half and then 

connected to the panel and then to the wire. I used wire connectors that were 

crimped to the positive and negative wires and then to the fan and pump wires and 

switches. When I placed my panels directly on the roof I ran the positive and 

negative wires over the eave and along the outside wall to the cooler. I placed the 

wire in flex tubing to make a neat job. There was an existing hole on the top corner 

of the cooler that I could run the wires into. The negative wire went to a common 

ground which then went to the fan and pump. The positive wire was run to the two 

switches that control the fan and pump. The wires were passed through an opening 

between the inside of the cooler and the portion that goes into the window where 

the existing 110 AC volt wires were run. They were connected to the switches and 

back to the fan and pump. I used tie connectors to keep the wires in place and neat. 

I do not use a voltage regulator on my cooler. The fan and pump seem to work fine 

without it. There are some panels that have built in regulators. They might function 

the best. 

A LITTLE ABOUT EVAPORATIVE COOLERS 

Evaporative coolers perform best when the humidity is low. On days when 

the humidity is really high, the house can feel muggy inside. For those who have 

another type of air conditioning system, that will be the time to use it. For the drier 

days the evaporative cooler can do quite well. If you can, place the cooler in a 

window that is shaded. The sun baking on the metal surface can reduce the 

effectiveness. I actually don’t have mine shaded, but you should do what I say and 

not what I do. 

Evaporative coolers draw air from the outside and as it passes through the 

pads it is cooled and blown into the house. It is best to close all the windows in the 

house except for one that is farthest from the cooler. I open the back bathroom 

window about half way. You can feel the air exiting the house at the window. I 

place a piece of toilet paper up to the screen and it will stay in place from the 

exiting air. 

The cooler is a little noisy and it can be irritating when the sun goes behind a 

cloud and the fan slows down and then speeds up when the cloud goes away. 


The following is a partial list of items that you will need. 

Materials: Purchased at: Price 

New Evap cooler 3000CFM Wal Mart, Lowes, 

Home Depot $ 200-300 

Evap cooler you have Home $ 0 

12 Volt radiator fan Internet, Kragen’s $ 35-80 

12 Volt bilge pump Wal Mart $ 14 

(2) 12 Volt switches Radio Shack - Kragen’s $ 4 ea 

12 gauge wire Radio Shack - Kragens $ 10/25feet 

Additional hose for pump Hardware store $ 2 

75 to 125 watt 12 Volt solar panel Internet $ 400-600 

Wire connectors, flex tubing to cover wires, sheet metal screws, fuse and 

fuse holder, tie straps to make a neat job and keep wires in place. Good Luck!

Build Your Own Solar Evaporative Cooler - Survival-training.info

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