Back from an early morning walk with her dog, Cokey, Louise Meyer starts to make dinner. It's 7:30 a.m., the sky is clear and she can already feel the intensity of the sun. No, she's not a overachieving super chef. She's just taking advantage of the daylight.

Inspired by a recent meal at a French restaurant, Meyer decides on a menu that includes Gratin Dauphinois and Tomates Provencales. She heads to the ground floor kitchen in the back of her three-story Mount Pleasant town house. She has no need today for the gas stovetop or the electric convection oven so she heads straight to the cutting board. She slices some potatoes and layers them in a buttered black-enameled pot along with crushed garlic, salt, pepper and grated Gruyere. She pours milk on top and sets it aside. Another pot she fills with halved tomatoes, topped with garlic, fresh oregano and basil, freshly ground pepper and a drizzle of olive oil. She puts each pot in a plastic oven bag (the kind some people use to cook a whole turkey) and ties each off with string. Holding the stacked pots, she carefully mounts the two flights of wooden stairs through her 100-year-old home. She is heading for the top of the house.

On the third floor, Meyer walks to the back of the house, where an east-facing window opens onto the roof over her second-floor office. She places each pot in an aluminum-lined contraption, pushes them out the window and onto the roof, turns them toward the south and closes the window. It's only 9 a.m., but when she returns that afternoon -- voila! -- her dinner will be ready. This is the regimen of a solar cook.

"I feel guilty when the sun's out and I'm not using it," she says. "You get obsessed and you can't stand wasting the sun."

Meyer, 58, first heard about solar cooking while living in Switzerland in the mid-1980s, but it wasn't until Earth Day 1990 that she decided to learn how. The process not only protects the environment by using a natural source of energy instead of pollution-producing fuels, but also saves Meyer money on gas and electricity.

"I like getting things free," says Meyer, who also dries her laundry on a backyard line and rarely uses the one air-conditioning unit in her office. She estimates saving $140 during summer months and $40 in winter months on her utility bills.

With a tree-covered back yard, Meyer decided the roof -- with full sun during the prime hours of 10 a.m. to 2 p.m. -- would be the best place to bake, steam, simmer and roast a daily meal. But she needed a cooker.

Through Solar Cookers International (SCI), a nonprofit research, educational and outreach organization in California, Meyer found many different styles. Most cookers are blindingly reflective contraptions and can look like a funnel, a pizza box or a satellite dish; they're made of cardboard or clay -- one is even made from dung and mud!

The organization's Web site -- http: // solar cooking. org -- provides instructions for building homemade cookers, but it also sells a simple model called a "CooKit," a three-sided panel of aluminum-lined cardboard that surrounds an ordinary cooking pan or pot. When weather conditions are met, the contraption can reach a temperature as high as 300 degrees (although Meyer says she can't reach that temperature on her roof). When not in use, the CooKit folds up flat to store easily.

A dark, light-weight and shallow pot -- like those speckled metal ones sold in hardware stores for camping -- with a tight-fitting lid will get hotter than the more expensive pots and pans found in most kitchens. The pot is wrapped in a roasting bag or covered with a glass or clear plastic dome such as an inverted salad bowl to create a seal that retains the heat. A raised trivet or a few rocks underneath allows hot air to circulate around the pot so food cooks evenly. In order to maintain the seal, stirring is discouraged.

Solar cooking is safe as long as the raw food is cooked thoroughly and reaches the internal temperatures that are recommended for food safety. It is often compared to using a slow cooker such as a Crock-pot, but Meyer says you can do anything except fry if you have the right kind of cooker. She has made everything from salmon to stuffed peppers, lasagna to banana bread. And it all tastes as if it came from the kitchen. The CooKit won't bake a sheet of cookies; for that, Meyer suggests another contraption -- a banana box oven. With a box from the local grocer, some aluminum foil, clear plastic and newspaper (for insulation), you can rig a solar oven to bake cookies.

Meyer says the easiest things to cook are soups, stews or eggs (they're baked, but turn out similar to hard-boiled with a suntanned shell), but she suggests starting with rice, because mastering this simple food teaches the basics of solar cooking. Her rice didn't come out fluffy right away, so when the rice was sticky, she had to determine why. Is the angle of the cooker off? Is it too cloudy?

Meyer always gets her food out before noon and angles the cooker toward where the sun will be at noon. Her rule of thumb: "You should be cooking during those hours that your shadow is shorter than you are."

The height of the local cooking season is April to October, because the angle of the sun is stronger, but the weather is the most important factor in solar cooking. Meyer says you need at least 40 minutes of sun every hour. If it gets too cloudy, it's best to resort to kitchen appliances to finish off the meal. Meyer says high winds and Washington's trademark humidity are challenges -- the temperature in the cooker doesn't get as high, because the wind and humidity seem to block the sun's rays.

In general, food in the solar cooker takes twice as long as in an oven. Meyer has developed a feel for timing based on the weather, although she usually puts a thermometer in the bag around the pot, just to see how hot it is. She says the thermometer never goes higher than 250 degrees on her roof -- hot enough to cook anything if given enough time, but never hot enough to make food burn. Meyer admits when she first started, a lot of dishes failed, but SCI's tips helped her get beyond that sticky rice.

"It requires flexibility and curiosity," she says.

For Meyer, solar cooking is more than fun, free and easy. Three years ago, she and her friend Darwin O'Ryan Curtis, 75, founded Solar Household Energy, Inc. (SHE) with another partner to promote solar technology to entrepreneurs in countries where cooking fuel -- often firewood, charcoal or gas -- is scarce and expensive.

Meyer often invites friends and acquaintances for solar-cooked dinners at Curtis's Chevy Chase home. In his sunny back yard, they make a show of opening a steaming pot of rice, pulling apart a tender roasted chicken or taking a boiling pot of ratatouille out of the sun.

SHE has programs in Bolivia, Burkina Faso, Egypt, Haiti, Senegal and Turkey to encourage residents to buy solar cookers and become self-sufficient. "We're going for the most deprived people in the world," Curtis says.

When they demonstrate how to use the cookers, they prepare foods that are staples for the local people. At their backyard cookouts to teach Washingtonians about the ways of the sun, they usually cook chicken.

Curtis says chicken is easy to cook when it has the little pop-up timer, so you know when it's done. At one dinner, he says, the meal was so overcooked that "when it came time to feed everybody, Louise stuck a fork in the chicken and all that came out [of the pot] was the bones."

Meyer and Curtis both work from home, so keeping an eye on the cooker is easy. To turn down the heat, yet keep a dish warm, the cooker can be angled away from direct sunlight. Meyer estimates it took her a couple months to get the swing of solar cooking.

Curtis, who rigged up his first solar cooker from a banana box, admits mishaps of his own. He forgot and left a leg of lamb in the cooker for more than six hours recently. Once he remembered, he found it to be shriveled and hard on the outside, stringy on the inside. But the relative ease of solar cooking is what keeps Curtis doing it.

"I'm lazy. I do it out of sloth . . . when it's time to have supper, I just go out and fetch it, and it's done," he says.

In countries where the sun is strong and clouds seldom come, people can cook two meals per day and pasteurize water. But Meyer says the largest obstacle is that people don't want to change their habits.

Now that solar cooking is part of Meyer's lifestyle, she has a hard time on rainy days. Better than resorting to the kitchen stove is a dinner of a salad with crusty bread and cheese.

For more information on Solar Household Energy, Inc., visit www.she-inc.org.

Using a reflective box, Louise Meyer takes advantage of solar power to cook dinner on the roof of her house in Mount Pleasant.Louise Meyer helped found Solar Household Energy, Inc. to promote solar technology in countries where fuel is scarce.