Frame of Reference

• The reference table used by the "Consumer Guide to Home Energy Savings" estimates the cost of cooking a traditional casserole for an hour in a moderately heated (350 degrees) gas oven and electric oven. The guide bases its figures on electricity costing an average of 8 cents per kwh (kilowatt-hour) and gas costing 60 cents a therm. A kilowatt-hour is the amount of electrical energy consumed when 1,000 watts are used for one hour. One therm equals 100,000 British Thermal Units (Btus).
  
  

Electric vs. Gas Ovens

• To operate an electric oven for an hour at 350 degrees F costs 16 cents and uses 2.0 kWh. A gas oven set at the same temperature for the same amount of time uses .112 therm and costs 7 cents.
  
  

Energy Efficiency Guidelines

• Preheat ovens only when required, which is typically only for baking breads, cookies or pastries. Don't preheat the oven longer than necessary. Casseroles and slow-cooked foods such as roasts can usually be put into cold ovens and slowly brought up to the recommended temperatures as the oven preheats.
  
  Use a timer to track suggested cooking periods. Avoid opening the oven door more than necessary because the temperature drops around 25 degrees each time and increases the baking time. When possible, bake several items at once, Use glass or ceramic pans, which allow you to reduce the temperature about 25 degrees. Do not cover oven racks with foil because this deters the flow of heat in the oven and creates unevenly baked dishes. Stagger pans on different level oven racks when baking to increase airflow. Check seals on oven doors, and replace cracked or torn ones to prevent heat loss and increased energy consumption.
  
  

Energy Saving Options

• Besides conventional gas and electric ovens, there are other baking options that save energy. An electric convection oven circulates heat more evenly and cooks a casserole at temperatures 25 degrees lower (325 degrees F) than conventional ovens in about a quarter less time. It uses 1.39 kwh and costs 11 cents for 45 minutes. With a toaster oven, it takes a temperature of 425 degrees F to cook a casserole, but the appliance uses only .95 kwh and costs 8 cents for 50 minutes. Microwaves are among the most energy-efficient electric ovens, using .36 kwh to cook a casserole on high for 15 minutes at a cost of 3 cents.