According to the Food Safety and Inspection Service, microwave ovens are one of the greatest inventions of the 20th century. A fixture in most modern kitchens, they are versatile pieces of equipment. Not only can they be used to bake, boil and steam foods, they can also reheat foods quickly and efficiently. Domestic appliances vary in power output from 650 watts to 1,200 watts; the higher the wattage, the quicker the cooking time. Despite their versatility, all microwave ovens cook at slightly different rates. In addition, although many recipes are written for 800-watt ovens, yours may be a higher or lower power rating. It is helpful, therefore, to be able to adjust cooking times correctly to ensure perfect results no matter which recipe you use.
Determine the power rating of your microwave oven. Check the instruction manual or look for the information label on the machine.
Test the power-output level of your oven by pouring 1 cup water into a glass measuring cup. Place the cup into the microwave and heat the water on full power for four minutes. Note the amount of time needed to boil the water. If the water boils in less than two minutes, your oven has more than 1,000 watts of power. If it boils in 2 1/2 minutes, the power is 800 watts; three minutes, 700 watts; and more than three minutes means it is 300 to 500 watts.
Check the microwave power rating for the recipe you are using. This will usually be stated in the recipe or at the start of the book, perhaps in the introduction. Recipes contained in one book will usually use the same power rating for all recipes, typically 850 watts.
Adjust the cooking time for your oven. No adjustment is required if the power rating of your machine is the same as the recipe. For every 50 watts your oven is higher than the one quoted in the recipe, decrease the cooking time by five seconds per minute. For example if your oven is rated at 1,000 watts but the recipe quotes times for an 850-watt oven, decrease the cooking time by 15 seconds per minute. For every 50 watts that your oven is lower than the one quoted in the recipe, increase the cooking time by five seconds per minute.