For days when the sun doesn't shine, you can always go back to your regular stove and use some of the electricity or gas you have saved. Solar ovens have come on the market which are built and designed to perfection. Or you can build your own in an evening or two. In third world countries in Africa and Asia where fire wood and other cooking fuel has become too expensive or is increasingly unavailable, a solar oven made out of whatever materials are at hand is a marvelously simple and efficient alternative to traditional methods of cooking. Water is also easily boiled and sterilized, thus reducing illness and in fact saving many lives.
Some units have huge polished aluminum reflectors and many other sophisticated features.
They can develop temperatures of 350-400 degrees depending on how you adjust the angle of the reflectors toward the sun. There is now a number of different solar oven kits available. They range from small, portable units for camping and even backpacking to large, home units.