All About Solar Cookers 7



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Conservation Programs Credits
A publication of the Arizona Department of Commerce Energy Office
3800 N. Central Ave, Suite 1200
Phoenix, Arizona 85012
(602) 280-1402
or call toll-free in Arizona
(800) 352-5499

Fourth Edition: October 1994

Editor: Jim Arwood
Written by: Jim Arwood and Norma Dulin Gurovich
Layout and Design: Shauna Obergfell
Solar Panel Cooker Layout & Design by: LeAnn Moorehead 

Some of this information was copied from publications by Citizens for Solar, Tucson, Arizona, Solar Box Cookers International, Sacramento California and Solar Box Journal, Seattle Washington.

All About Solar Cookers 6


Overcoming fuel shortages in developing nations 

The energy problem is far more extreme in less-developed parts of the world than in the United States. In places like eastern Africa, natives have trouble finding sufficient firewood to cook dinner or heat water to kill bacteria. Women sometimes walk 20 to 30 miles to obtain only a two-day supply of cooking fuel.

The simple solar box cooker is helping people to stay healthy in places such as Zimbabwe, Bolivia, Guatemala, Kenya, Haiti, and Pakistan. In Botswana in 1988, for example, solar box cookers were introduced because of a 50 percent malnutrition rate. This devastating health problem was not caused by food shortages but by a lack of fuel.

Two Arizona women created these cookers, Barbara Kerr, a nurse from Taylor, Arizona, and Sherry Cole, a former freelance writer from Tempe. Their solar box cookers reach temperatures as high as 325 degrees Fahrenheit and easily kill cholera bacteria at 150 degrees. The cookers are constructed with two corrugated boxes, one smaller than the other, 100 feet of aluminum foil, a pint of glue, a lot of newspaper, and a sheet of glass.

Kerr, and Cole’s first box cooker was created in the 1970s, and the first sale went to microbiologist Bob Metcalf of California University in Sacramento. Metcalf formed the organization Solar Box Cookers International in 1987 to promote the cookers for health and environmental benefits worldwide. The group’s expeditions have received support from the Pillsbury Co. Meals for Millions Applied Nutrition Project, Foster Parents Plan and Food Industry Crusade Against Hunger.

In Guatemala in 1988, Metcalf introduced solar box cookers to women in rural areas who spent one-third of their time gathering firewood. So many trees had been chopped-down that hillsides were eroding during seasonal rains and ecosystems had been destroyed.

Most people in Kenya do not have electricity and many do not have running water. Before the box cooker, meals were often prepared over a stone hearth with a wood fire. Solar cookers reduced the need for constant, tedious fuel gathering.

Solar cookers offer many other benefits to people in developing nation. They eliminate the toxins common to foods cooked directly over a fire and prevent health problems caused by constant exposure to smoke and fire.

The cookers are also used to heat and purify water. Bacteria in water are a primary cause of chronic diarrhea, which contributes to thousands of cases of infant malnutrition and death.


Next Article: - All About Solar Cookers 7 - Making a Solar Panel Cooker

All About Solar Cookers 5


Solar cooking tips


· Solar cookers may not look hot, but temperatures of 120 to 425 degrees will certainly burn your fingers. Use potholders.

· Intense reflected light could permanently damage your eyes. Children in particular have a tendency to stand in the brightness of reflected light and should be carefully watched around solar cookers.

· Keep the lid closed so that appetizing fumes, do not escape into the air and attract animals and insects. If a curious animal does approach the cooker, a closed lid prevents unwanted dinner guests. 


Solar chefs are limited only by their imagination. Almost any dish becomes a delicious treat when cooked in a solar cooker –beans, bread, cookies, roasts, vegetables and many others. 

Most standard recipes translate favorably to solar cookers but require less water or liquid. Solar chefs also find they need less salt and sugar in solar-cooked foods because of the gentle cooking process.

Temperature and Timing:

Solar cookers should be placed in the sun and preheated for at least one hour before placing food inside. Many, high-quality solar cookers reach temperatures of 350 to 425 degrees or more and cook dinner in the same amount of time as conventional ovens. Other models reach temperatures of only 150 degrees. A barbecue thermometer is a useful tool. 

To reach maximum temperature and fastest cooking time, the cooker should be aimed directly at the sun. It should be turned every 20-30 minutes to maintain a direct angle. Some solar chefs setout cookers in the morning, aiming them toward the sun’s midday position. By late afternoon, dinner is ready to eat without ever refocusing the cooker.  

Cooking between the hours of 10 a.m. to 2 p.m. is best in Arizona’s winter months. In summer, the sky’s the limit!


Clear weather is essential. On partially cloudy days, solar cooking takes longer. On extremely cloudy days, we suggest that you rely on the old energy-consumer standbys like house ovens or barbecues.

Outside temperature has little effect on solar cooking; if the sky is clear, you can cook on a snowbank high in the mountains.

Pots and other utensils:

Use either dark, or clear glass pots when cooking in solar cookers. Dark pots absorb light readily and clear glass allows light to directly reach the food. Avoid foil or aluminum containers that reflect light away.

Closed containers hold-in heat and will cook food more quickly. Some people even use canning jars. Brown-in bags are excellent for cooking meat.

Cooking times: (NOTE: 450g = 1 lb)

Potatoes (300g + 1 spoonful water) 2 hours
Carrots (250g + 1 onion, no water) 2 hours
2 eggs (+ 1 spoonful water) 1 hour
Lentils (100g + 250g water) 1.5 hours
White rice (80g + 160g water) 1.25 hours
Brown rice (80g + 160g water) 2 hours
Red beans (100g + 200g water) 2.5 hours


Next Article: All About Solar Cookers 6 - Overcoming fuel shortages in developing nations 


All About Solar Cookers 4


Design of Solar Cookers

The Box Cooker

The seemingly simple design is actually a family-sized cooker that can handle an entire meal on a sunny day. It features an insulated box with a glass or heat-resistant plastic cover that also serves as an oven door. Sunlight passes through the glass or plastic into a dark cooking area.

Additional sunlight is reflected into the box cooker by a shiny lid attached to the box. 

When in use, supports made of cord and wood hold the reflector above the cooking area.

Cardboard box cookers are light, compact, and easy to store or move. Heavier wooden models are more useful for the backyard or patio. Depending upon their construction, these cookers typically reach temperatures of 120 to 225 degrees.

Slant-Faced Solar Cooker

Many do-it yourself buffs choose the slant-faced solar cooker. These are often highly efficient cookers and very portable, folding to a size of a suitcase.

Hinged reflectors direct the sun’s rays through a slanted glass lid. Some reflectors are made of shiny aluminum; others are mirrored or use aluminum foil glued to a sturdy backing. The reflectors are usually collapsible, folding and clamping onto the top of the cooker for easy carrying

To use, the slant-cooker-face is pointed toward the sun and the reflectors are secured in the open position. Some cookers feature built-in height adjusters for more direct aim at the sun.

Multi-Mirrored, Cone-Shaped Cooker
The cooker style features many small mirrors, curved in a cone-shape around the cooking area. This reflector often spans four feet in diameter and with a lid can double as a patio table.

These cookers reach temperatures, of 300 to 450 degrees and cook food in the same time as a conventional cooker. The cooking area is large enough for a turkey.

Concentrating Cookers

Concentrating cookers, or “hot plates,” employ dish-shaped reflectors aimed at the sky like radio receivers. The reflector is designed so that direct light bounces on to a single point. At this point, a cooking stand holds a pot of food or water. The stand can be attached to the collector or be separate.

Concentrating cookers can generate temperatures of 600 degrees Fahrenheit or more and must be constantly attended as the sun moves across the sky. The reflector must be repositioned to follow the sun and keep the focal point on the food being cooked. When left unattended, concentrating cookers have been known to set wood on fire and even burn the ear of a curious dog unlucky enough to be in the wrong place at the wrong time. These cookers also have a dangerous tendency to tip in windy weather.

Next Article: All About Solar Cookers 5 - Solar cooking tips