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?
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, much of the heat is lost around the sides of the pot. 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 central 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 important.
It is not always a simple decision as to when it is best to use a smaller countertop appliance instead of the range or oven. 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.
Whenever possible, select small countertop appliances which 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.
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%.
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 which 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.