Learn how to make a DIY solar oven that works! With just a cardboard box and other common household items, you can make yummy s’mores with your own solar oven.
One of the most fun ways to reuse cardboard boxes is to make a homemade solar oven. Especially in Arizona where the sun is out all summer long, we have lots of chances to use our little solar oven and experiment with different food items!
You might be a little skeptical about solar ovens. Do they really work? Well we have tried and tested s’mores and even cooked an egg with our DIY solar oven, so I am here to tell you that they do work!
The most popular material to use for the solar oven is a pizza box. This is just because the pizza box has a lid that you can open and close easily to seal in the heat. But you can really do this with any box, you would just have to do the extra step of securing the lid to the base box with tape.
We were happy that we could reuse our KiwiCo box (best STEM subscription box ever, by the way!) because it has a convenient lid like a pizza box but without all the grease!
How to Build a Solar Oven
- Large box
- Aluminum foil
- Knife or scissors
- Plastic wrap or clear plastic bag
- Black construction paper
1. Use your ruler and pen/pencil to trace out a rectangle on the lid of the box. You should leave about an inch between the edges of the rectangle and the sides of the lid.
2. Use a knife or scissor to cut along 3 sides of the rectangle, leaving the side closest to the edge where the flap would bend to open up uncut. Adult only, please!
3. Line the bottom and walls of the box with aluminum foil. Use tape to hold everything in place.
4. Cover the top flap with aluminum foil. You just need to cover the inside of the flap, but I find it easier to just cover the whole flap and then secure with tape.
5. Cover the opening of the lid with plastic wrap. Use tape to seal the wrap all the around the opening to retain heat.
6. Place a piece of black construction paper at the bottom of the box.
7. Use a wooden stick or skewer to hold the top flap open. Be careful not to pierce the plastic wrap.
Your solar oven is done! Continue reading to find out our experience making s’mores in our DIY solar oven.
How to Make S’mores in the Solar Oven
To make yummy s’mores in the solar oven, simply gather the s’more supplies: graham crackers, chocolate bars, and marshmallows.
I like to place a small piece of aluminum foil underneath the s’mores so that you can take them out easily without making a mess. You can skip this step. If you decide to use foil, just make sure it’s not covering too much of the black construction paper.
After you build the s’mores in the solar oven, close the lid and prop up the top flap with the wooden stick. Place the box in the sun and wait about 30-60 minutes for the chocolate and marshmallow to cook.
Funnily, the moment we went outside with our solar oven, clouds came and it wasn’t as sunny as usual. The sun appeared here and there but it was definitely not a usual sunny day in Arizona. Fortunately, there was enough sun to melt the chocolate and soften the marshmallow to make a delicious s’more.
Do be careful when you touch the solar oven after it has been out in the sun for a long time. It does get pretty hot, especially when you open it and try to take out the s’mores. I suggest using oven gloves and letting the s’mores cool down slightly before letting your kids dig into them.
Of course, the perfectionist in me was not satisfied with this result. So we tried the solar oven experiment again the next day when it was very sunny out. We also didn’t put the graham cracker on top of the marshmallow, thinking that more direct sunlight would help melt the marshmallow more.
Everything seemed to be going well, but then I noticed that ants were starting to head toward the solar oven. So we moved it to our sports court, away from the insects!
When you place the solar oven in the sun, you want to make sure that the top flap faces the sun so that it can reflect the ray into the opening of the box. The shadow of the box should be behind the solar oven.
This time, the s’mores took only 30 minutes to cook with the sun bright in the sky. The marshmallow and chocolate were nicely melted, much more so than the s’mores we tasted the day before!
On both days, we had very similar outside temperatures. But one day was slightly cloudy while the other was very sunny. This shows how the solar oven really works and how it converts the energy from the sun to the s’mores!
How Does a Solar Oven Work?
The light from the sun enters the solar oven in two ways. First, the sunlight goes directly through the plastic wrap to the black construction paper, which partially transforms into heat. Second, when the sunlight hits the foil on the top flap and walls of the box, it bounds off these surfaces and more light energy is transferred to the s’mores.
The plastic wrap helps trap the heat inside the solar oven, just like the door of your baking oven at home. Now you have the light energy from the sun converted to heat energy inside the box to melt the chocolate and marshmallow.
How Hot Can a Homemade Solar Oven Get?
There are many models of a solar oven out there, and one with more extravagant design can heat up to 300 degrees F. Those ones have extra panels that help reflect sunlight into the oven.
A simple solar oven like the one we built above can heat up to 160 to 200 degrees F. Unfortunately, I did not have a small thermometer I could put inside the solar oven to measure the temperature myself. If you do, I strongly throwing one in the solar oven with the s’mores to see how hot your solar oven can get!
What can you cook in a DIY Solar Oven?
There are lots you can cook in a solar oven. Keeping in mind that it can heat up to 160 to 200 degrees F, think about what food you would cook at that temperature. Due to food safety, you probably want to stick to easy recipes like nachos and mini cheese pizzas.
We did try cooking an egg in the solar oven, and the result was not so appetizing.
The problem was that even though the egg did eventually cook, the long cooking time dried out the egg.
We tried again and took the egg out before it dried out, but the inside of the egg was not cooked. Interestingly, the top layer was hard, and to break the yolk with a knife was like breaking a thin candy shell.
Even though cooking an egg in a solar oven did not work out for us, I recommend trying it with your kids just for fun!