So, coming from a time when most cooking was done with dial choices of "Low," "Medium," and, "High," and having worked on my grandmother's wood stove learning where the "Slow," "Moderate," and "Hot" parts were, it's hard to understand a dependence on numbers that may or may not reflect an actual temperature.
Although older electric stove models were available, this was my first apartment stove before becoming a homeowner in the 60s. Apparently, the landlord firmly believed in the, "if it ain't broke, don't fix it," philosophy. Nothing like my mother's GE stove. Definitely a step up from the wood stove but a learning curve, nonetheless. You could move a pan from its position on a wood stove and stop the cooking. The electric stove retained heat long enough to oftentimes overcook delicate sauces and baked goods. But, we all adjusted.
My first stove from hubby had all these wonderful buttons -- still, WM to HI but, now, they had added numbers 2 and 3 for medium choices. As in the old days, trusting my eyes, nose, touch, and toothpick, told me when the cooking was done. Probe thermometers were added to my accessories, as cook books began to line my shelves. Even though recipes in print and on boxes might tell me what temperature to use, there were many times when either the recipes needed additional time or my oven's uniqueness required pan rotations to get things done. Here is a wonderful article on how recipe temperatures came to be and, as it turns out, it was a post-WWII marketing need.
So, I entered solar cooking with little or no more expectation than having my meals cooked using a different energy source.
Today, we find hundreds of Crockpot® and slow cooker recipe books available because of the convenience and discovery of just how delicious food can be when cooked at lower temperatures. This has made my job so much easier. Now, I'm able to help my visitors understand that solar cooking is best described by imagining a Crockpot® -- on "speed!" Folks from the 60s and 70s enjoy the comparison and, if you don't get it, you might have to hit the history books for a refresher.
Once my visitors know that most solar ovens (even the cardboard and tinfoil types) have a low temperature of around 200°F to 225°F and those temperatures are still higher than the national standard High of 190°F+ of a slow cooker, they become more open to the idea of solar cooking.
As an example, most slow cooker recipes give timings between 3 to 4 hours on the High setting and 8 to 12+ hours on the Low setting. If you were to prepare your foods in the same way but use a solar oven, your average recipe would be cooked in just over 1-1/2 to 3 hours at 225°F and 4 to 7 hours for denser recipes.
The majority of homemade solar oven users say that the highest temperatures reached on a regular basis are between 225°F and 275°F. Sharon Clausson, inventor of the Copenhagen Solar Cooker, has shown with oven thermometers that her oven often reaches temperatures of 350°F to 375°F. (And, I believe, in one instance when it was almost 475°F!) More often than not, she uses a combination of a cooking vessel inside a "ball" of glass bowls clipped together, creating an insulated oven chamber. Other cardboard and tinfoil ovens will reach varying degrees from 200°F to, in some instances, 300°F, depending upon the size and height of the oven and its reflectors. Sharon Cousins, inventor of the EZ-3 Solar Cooker , can alter her oven temperatures by the size of the box corner used. In all cases, however, these temperatures can only be achieved by either placing the cooking vessel inside an oven bag or enclosing the open side of the solar oven in double (for best results) oven bag layers to create the baking chamber environment.
Commercially-built solar ovens available today are insulated and reach very high temperatures. The Global Sun Oven® boasts a potential high of 400°F; but, as with conventional ovens, once the cooking vessel has been placed inside, the temperature drops almost 15 to 25 degrees, not returning to the higher temperature until both the food and vessel have equalized in the cooking chamber. Foods placed in a Crockpot® are heated to the full height of the food from the outside in and it isn't until the center has reached the same temperature that cooking begins. Foods in a solar oven cook from the top down but that environment is easily changed by either placing the vessel on a heated base or preheating the foods through recipe construction, hot liquids, and/or the microwave to get the process started. If you're cooking away from home, you are restricted by the environment and should expect longer cooking times. Regardless of time of year, the best solar cooking time is between ten a.m. and two p.m.
The most obvious difference between a commercially-built solar oven and a slow cooker is that solar cooking is FREE, every time. And, you know how I love that! Solar cooking is a moist environment with little, if any, evaporation. Even though you can leave food unattended in a slow cooker, most do not stop cooking until they are manually turned off or unplugged. The food can be overcooked, dry, and even burnt, as the liquid evaporates. It is very difficult to overcook or burn recipes that are solar-cooked. When the food is cooked, the temperature will drop to a warming temperature from 180°F down to 150°F until you retrieve it. I believe it's condensation that forms on the underside of the oven door when the food has been cooked that causes enough filtering of the solar rays to turn the oven into a retained heat chamber.
This is why I don't worry about the cooking temperature in my solar oven because I know the food will be cooked at a temperature much higher than the average slow cooker. Unfortunately, it's very hard for today's conventional cook to accept that, until they've personally experienced a solar-cooked meal. In my opinion, every family should have some form of solar oven available for nourishing hot meals during long-term power outages to feed their families, to pasteurize their drinking water, and, if necessary, to sterilize utensils.
In trying to bring solar cooking to the mainstream, my sincerest wish is for the home cook to make it an accessory appliance as opposed to an adversarial product that has to keep proving itself. Every new appliance has its own learning curve and comes with a booklet not only describing its use but includes recipes to help the consumer discover the potential. That's all I'm asking, is that you give a solar oven the same opportunity. There will be days when using the sun to cook your meals will not be feasible and my suggestion would be to use those appliances that draw 110 volts, if possible. It's all about saving money, reducing fossil fuel usage, and feeding your family healthy and nutritious meals. And, you know what? It's still the best kept secret from the mainstream cook.