Microwaves cook food by heating the water, fat and sugar within it [1], therefore most foods can be cooked in them. In 2006, Defra produced a report on the amount of energy used when cooking food (in portion sizes ranging from one to four) in a microwave, compared to that consumed when cooking the same food using an electric oven or stovetop with an EU energy rating of A, the most energy efficient type on the market. Figures were not available for comparison of electric or microwave ovens to gas ovens, or usage of fan-assisted electric ovens, and it was difficult to make precise calculations without detailed information on user habits. However, Defra estimated that if 20% of cooking was switched from electric ovens to microwaves, the energy saving would be at least 10% [2].
The microwave versus stovetop test
Some foods, such as whole chicken, were tested in a combination microwave oven, which can cook by convection as well as microwaving. Food types that were tested in a standard microwave oven versus cooking on a ceramic hob were milk, porridge, new potatoes, frozen vegetables, baked beans and fresh salmon fillet. The potatoes and frozen vegetables were microwaved in a little water, and the salmon was microwaved with no water, while each of these food types was immersed in water when cooked on the stovetop. Non-stick pans with copper-coated bases were used on the stovetop, appropriate ring and pan sizes were chosen, power settings were adjusted once water started to boil and lids were used on pans containing the new potatoes and frozen vegetables.
Microwave versus stovetop results
For the porridge and baked beans, the amount of energy used by microwave cooking was the same or more as when cooking on the ceramic hob. For the other foods that were tested, the energy savings (which are given as a range where they varied by portion size and microwave settings) were as follow:
- Milk – 25-50%
- New potatoes – 70-75%
- Frozen vegetables – 65%
- Fresh salmon fillet – 63-78%
The microwave versus electric oven test
Foods that were tested in a standard microwave and in an electric oven were baked potatoes, lasagne, an Indian ready meal, a frozen one portion ready meal and frozen pizza. The oven had a medium sized cooking compartment and was not pre-heated, so that all consumed cooking energy could be recorded.
Microwave versus electric oven results
Cooking the frozen pizza in the microwave did not save energy compared to cooking in the electric oven (although using the combination microwave did, by 22%). For the other foods tested, the energy savings were:
- Baked potatoes – 21-61%*
- Lasagne – 40-81%
- Indian ready meal – 38-63%
- One portion ready meal – 55-73%
*The baked potatoes were tested in both a combination and basic microwave oven, and the results do not specify the exact energy saving for each
Therefore, over time substantial energy savings can be made by using a microwave, and that means lower energy bills too. Defra [2] stated that microwaves are often not used as a primary cooking appliance, and that habit is a large contributing factor when people are reluctant to use microwaves, along with concern over learning a new cooking method. However, microwaves are not difficult to use and are safer than having flames or cooling cooker rings exposed. There are microwave cooking recipe books and various products available to aid their use and multiple food types can be cooked at the same time, as with a stovetop. Cooking times are often faster in a microwave, less water is needed, and water that is used does not need to be boiled, further increasing the environmental benefits of cooking with a microwave where possible.
[1] http://www.ctahr.hawaii.edu/new/resources/microwavecooking.pdf
[2] http://efficient-products.defra.gov.uk/spm/download/document/id/786
