Figuring Energy Consumption
The University of California at Santa Cruz estimates that a toaster oven uses about half the energy of an electric oven. But you can compute how much your appliances use with a simple formula. Multiply the wattage of your appliance by the time in use. Divide this by 1000. This gives you the kilowatt hours used. The U.S. Department of Energy says a toaster oven is rated at 1225 watts. Using it for half an hour would use .61 kilowatt hours. An electric oven set at 350 degrees is rated for 2000 watts. Used for the same half hour, the oven uses 1 kilowatt hour. Look at your electric bill to determine your cost per kilowatt hour.
In addition to the cost to operate the appliance, you need to consider how long it will take you to cook your food in a toaster oven vs. an oven. A small item may cook faster in a toaster oven than in a larger oven, where you need to allow extra time for the oven to heat to the proper temperature. But a larger item may cook faster in a full-sized oven, since the heat can surround it and cook it thoroughly without scorching the outside.
The energy costs associated with appliances can consist of more than the cost to operate an appliance itself. Both toaster ovens and ovens give off heat into the room. While this could be a good thing on a cold winter day, in the summer this heat makes your air conditioner work harder, expending more energy. An oven, being a larger appliance, puts off more heat than a toaster oven. So even if you have to run the toaster oven slightly longer than the oven, you can save energy on a summer day by not heating up your kitchen so much.
Whatever appliance you choose to cook your pizza or frozen dinner, don't sacrifice safety for savings. The exterior of a toaster oven can get very hot. Keep dishtowels, hot pads, curtains, plastic bags and anything flammable away from the toaster oven. Use only heat-proof pans in the oven and toaster oven. Don't allow food to drip onto the heating element of the toaster oven, as this could cause a fire. Don't leave food unattended in a toaster oven.