New, conventional residential stoves and ovens normally last about 20 years, so consider the purchase price as well as the operating costs when you make your selection. If your monthly utility bill significantly increases because of a new stove, a low purchase price is a nominal consideration. You can find a new range's estimated energy consumption on tags and stickers attached to the appliance.
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 -- 176 degrees C (350 degrees F) -- gas oven and electric oven. The guide bases its figures on electricity costing an average of 5p per kWh (kilowatt-hour) and gas costing 37p 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 176 degrees C (350 degrees F) costs 10p and uses 2.0 kWh. A gas oven set at the same temperature for the same amount of time uses 0.112 therm and costs 4p.
Energy efficiency guidelines
Preheat ovens only when required, which is typically only for baking breads, biscuits 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 14 degrees C (25 degrees F) 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 14 degrees C (25 degrees F). 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 14 degrees C (25 degrees F) lower than conventional ovens in about a quarter less time. It uses 1.39 kWh and costs 7p for 45 minutes. With a toaster oven, it takes a temperature of 218 degrees C (425 degrees F) to cook a casserole, but the appliance uses only .95 kWh and costs 5p for 50 minutes. Microwaves are among the most energy-efficient electric ovens, using 0.36 kWh to cook a casserole on high for 15 minutes at a cost of 2p.