Dear Jim: I prefer to use the kitchen range/oven for cooking, but heard using small countertop appliances is more efficient. Is this true, and is there a simple way to determine which appliances are the best to use? - Cari M.

Dear Cari: What makes one cooking appliance less expensive to operate than another is how much of the heat actually gets into the food and how much just ends up in the room air in the kitchen.

This is why it is important, for example, to match the size of the pot to the size of the burner/element on a range. If the pot is too small, as much as half of the heat is lost to the air. Also using the recommended type of cooking utensil material for the specific range top type is important.

During winter, the selection of the cooking appliance is not as important as during summer. Any heat which is lost to kitchen air just reduces the heating load on the furnace or heat pump. It is not a one-to-one trade-off, but it does reduce the heating cost somewhat.

During summer, any heat lost to the room air must be removed by the air conditioner. This makes it a double cost, so appliance selection is more important. Another consideration is overall cooking time to minimize the amount of water vapor given off. Using small appliances outdoors or a solar oven makes sense during summer.

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It is not always a simple decision as to when it is best to use a smaller countertop appliance. If the cooking time is the same as with the range element or oven, then the smaller, lower-wattage appliance generally will use less energy.

Another factor is the quality of the range and oven. If your range has a self-cleaning oven, it likely has heavier wall insulation, which saves energy. Minimize the use of the self-cleaning cycle because it uses a lot of energy.

Whenever possible, select small countertop appliances that have a thermostatic control for the cooking temperature. This provides more precise cooking than one with just a low-to-high temperature dial. A timer is also good to avoid overcooking and wasting more energy.

A small countertop convection oven uses much less wattage than the large oven. The oven's convection fan uses very little electricity and the circulating air cooks foods much faster for less heat loss to the room. Using a pressure cooker also reduces cooking time.

Microwave ovens use less electricity because they cook fast and nearly all the heat goes into the food items. If you can bake several dishes at once in the range oven, it will use less electricity than running the microwave several cooking times. Baking many potatoes is an example where the range oven is better to use.

To calculate the cost to operate an appliance, find the wattage rating on the nameplate. Divide this by 1,000 and multiply the result by your $/kwh electric rate to get the operating cost per hour. If the nameplate lists amperage, multiply it by 120 to get watts. For appliances with a thermostat, reduce the operating cost by about 50 percent.

Dear Jim: My asphalt shingle roof has black stains on it, and it looks bad. I cleaned it, but the stains came back. What is causing this, and is there anything I can put on the roof to stop the staining? - Robert M.

Dear Robert: The black stains are algae and fungal growth on the shingles from organic debris that settles on them. It usually is worse in shaded areas. Lay bare copper wire along the roof ridge. When it rains, copper ions flow down over the shingles and to retard this growth.

There are also DIY roof cleaning and stain-blocking chemicals from Saver Systems. Once the roof is cleaned, the stain blocker should be reapplied every two-three years.

Send inquiries to James Dulley, The Forum of Fargo-Moorhead, 6906 Royalgreen Drive, Cincinnati, OH 45244, or visit