Cooking
12% of Domestic Electricity Use
The Stove-Top
Little can be done to improve the efficiency of stove-top cooking.
Over 90% of Canadians cook with electricity. Electric ranges are inexpensive. They also cost little or nothing to install, where a kitchen gas outlet might cost $200 to $300.
Electric ranges depend on good contact between heating element and pot for effective heat transfer. If either the pot or the element are not perfectly flat, heat transfer will suffer.
Some models have solid, flat-milled heating surfaces. When used with similarly flat utensils, good contact and good heat transfer are likely. There are other ways to do an end-run around the contact problem. One of these is the infra-red hob where heat is supplied by a special element which heats the pot by radiation through a glass surface. There is no direct contact with the element, and the surface is very easy to clean. Another type is the induction element. This creates a strong alternating magnetic field in pots with a suitable (iron, steel & some stainless steel) base. They are controllable, heating and turning off instantly, and also have a smooth, easy to clean glass surface. Induction hobs are very rare in North America.
With a gas range, the hot gases make good contact, regardless of the condition of the pot – if the flame is set to be under, and not around it!
Whereas gas is burned to produce heat right under your pot, electric heat is what’s left over after a fuel (coal or uranium) is used in a distant power station. Less than 30% of the fuel’s energy reaches you as electricity. When you use electricity for heating, about ¾ of the energy in the original fuel is wasted!
The Oven
The efficiency of the oven has improved greatly over the years due to the self-cleaning feature. The self-cleaning process heats the oven to well above cooking temperature. To contain the high temperature (400oC / 750oF) safely, oven insulation was improved – yielding more efficient cooking. A modern, well-insulated oven probably uses half the energy of an older model.
The convection oven uses a fan to blow hot air around the oven. The moving air transfers heat to foods better than an oven without air movement. Recipes are modified for convection ovens by either lowering temperature or cooking time, slightly reducing energy consumption.
No estimates of energy use by older ovens is available. In any case, Canadians do little oven cooking – 20% use ovens less than once a week!
The Microwave
The microwave revolutionized the kitchen by allowing foods to be defrosted, warmed or cooked rapidly. Microwaves are high frequency radio waves (like radio or TV signals) similar to radar. Concentrated in a small box, microwaves generate heat in fats and water – thus warming foods. They also penetrate food somewhat, so energy is absorbed more efficiently than by surface heating.
Because microwaves heat the food, not the container, they warm small volumes quickly. Microwaves heat a cup of soup directly – needing half as much heat as stovetop warming would require. Although the magnetron tube (microwave generator) is only 60-70% efficient, it saves energy compared to heating both the food and a pot, which may weigh far more than a small quantity of food.
However, microwave ovens perform poorly at heating large quantities. This is because their power is limited. Popular models have 500-750 watts of power – much less than a 2000 watt stove-top element. Heating a kilogram of food in a pot is usually faster on a stovetop.
Used intelligently, a microwave can save some energy (money), but probably not a great deal. Use it to save time!
The Slow Cooker or Crock Pot
The slow cooker is a low wattage appliance (150-250watts). However, it is meant to be on for many hours, so its electricity consumption could be appreciable. Cheap models have little insulation. When buying, look for well-insulated models – for safety as much as for efficiency.
The Toaster Oven
These are usually poorly insulated. The unit’s appeal lies in its compact size, making effective insulation impractical. Many people think that cooking in a small tabletop unit saves energy. In fact, poor insulation means that operating a toaster-oven for 30 minutes may cost more than using a full-size oven. Use this appliance sparingly – only for toasting or short, re-heat jobs.