At present microwave ovens are not energy rated. Some do have a heating category to show how quickly food is heated. The rate is from A - E with E being the fastest. Microwaves are great for heating small amounts of food quickly. It is a very good way to reheat leftovers and ready meals.

More of us buying microwave ovens 

What happens when we cook food in a microwave oven? 

Types of microwave 

How we use microwaves 

Why don't we use microwaves for more of our cooking 

Energy efficient - but not rated 

Energy saving test 

The results of energy saving tests comparing microwave ovens with traditional electric ovens and hobs 

More research to establish maximum cost savings 

Making the microwave an even more popular choice 

Keeping microwave food nutritious 

Keeping microwave food safe 

More of us are buying microwave ovens

We are buying more microwave ovens, and we are buying more sophisticated models, which offer more choice in the way we cook our foods – and more opportunities to be energy efficient in the way we cook
In 2006, 82.7%, of people in Great Britain owned a microwave - just eight years earlier the figure was 70.6%. However, it hasn’t been an uninterrupted rise in purchasing – slightly more of us owned a microwave in 2004.Over the years, oven prices have fallen, there are more one-person households, and, of course, there is now a huge ready-meal market sector – all of which has affected our choice about what we eat and how we cook and prepare our food.But overall the sales of microwaves continue to rise and more of us are now buying the higher specification grill and combination microwave ovens These are ovens that have both a conventional convection oven facility and a microwave, which can be used together or separately to reduce cooking time,  save on power and reduce household energy bills.Busy lifestyles and the need to provide a variety of meals quickly seem to influence our decision. If we work, and if we have children, our ownership of microwaves is higher than average.  Now, with rising fuel bills, the need for energy efficiency and power saving may make microwave ovens an increasingly popular choice for even more of us.  

What happens when we cook food in a microwave oven?

While most people believe microwave ovens are energy efficient, some think that this is simply because microwave ovens cook more quickly and are smaller than conventional ovens. Microwaves ovens are certainly popular because they cook food very, very quickly. Yes, they are power saving, but energy saving features are a small part of the difference. They also cook the food in a completely different way. As everyone who has used a microwave oven knows, a microwave oven heats only the food - nothing else.  More than that – it heats food ‘from the inside out’. A conventional convection oven heats the oven and the outside of the food first – that’s why sometimes the outside of the dish has a crust, which is just what you want, but if you overcook it, the dish can ‘dry out’ and be less moist than you wish.  A microwave oven uses microwaves (or radio waves) in a specific frequency, so that the water, fats and sugars in the food absorb the microwaves.  This absorption converts them directly into heat. The dish remains moist inside, but if your microwave doesn’t also have a convection oven then you can’t get a crust, brown meat or bake potatoes. The radio waves used in microwave ovens are not absorbed by most plastics, glass or ceramics so they are ideal to use with a microwave oven. Metal pans do not work well in a microwave oven because they reflect the microwaves.

Types of microwave

There are three main types of microwave oven: microwave only, still the biggest seller (making up 68% of sales,), microwave oven with a quartz or radiant grill option (18% of the market, and combination ovens that provide both conventional heating and microwave cooking (14% of sales). Microwave oven power levels have increased  – many now have power ratings of more than 850 W, and even 1000 W.  While people take this to mean quicker cooking times, microwave instructions often recommend that you cook at settings lower than the maximum to ensure even heat distribution throughout the food5. The touch controls offer digital clocks and displays on most new microwave ovens.  On average, the standby power consumption of touch controls is 2 W but some are as much as 6 W, so for maximum power saving, use your microwave efficiently. While microwaves offer lower energy bills, many people find they take up too much space on the kitchen counter top. New developments in design mean that microwaves may soon take up less space on the kitchen counter top.  One development includes a microwave oven with a round cavity to increase capacity whilst minimising use of space on the counter top, internet microwave ovens that can be networked with other kitchen appliances and store recipes in their memory, a combined microwave oven and toaster, and a car battery-operated microwave oven.

How we use microwaves

A number of studies have tried to establish accurately how people use their microwaves.  Sometimes how we think we use it and how we actually use it are quite different.  For example, the majority of respondents in one consumer survey said they use their microwave oven mainly for reheating and defrosting (around 40% for each). However, when their actual use was recorded the defrost function was only used on a total of 6% of occasions logged.  The microwave oven was used for 20% of all recorded cooking activities (260 out of a total of 1,330 events). Studies have shown that microwave ovens are most often used for heating drinks (23%), followed by cooking or reheating vegetables (20%), cereals such as porridge (11%)  and meat (10%). Chilled and frozen ready meals were cooked by just under a third of participants9, but they made up only 4% of microwave uses. Participants in one recording study said that they use their microwave oven mainly because it is quick (87%) and easy to use (83%). Around one third of participants use a microwave oven because of power saving -  it uses less energy than cooking using a conventional oven or hob, with the potential for lower energy bills. Features that users value as most important on a microwave are touch control and defrost functions, which were the only features that more than 50% of users gave as important.

Why don’t we use microwaves for more of our cooking?

Most people are aware that microwave ovens can use less energy than other means of cooking, but recent research showed that only 16% of people consider themselves to be regular microwave users. And people only use microwaves, despite the obvious benefits of energy efficiency, for 20% of their cooking operations. We commonly use microwave ovens to reheat vegetables, and to cook cereals and meat. Nearly half of microwave users like them for reheating leftovers, but despite power saving, do not often use them for chilled and frozen ‘ready meals’.  A recent survey found that only 13% of users cooked their fresh vegetables in a microwave. Most of the microwave sales in the UK are for the basic microwave – without the convection oven. Most of the users of these tend to be older and less affluent than the average householder.   Although some research has assumed that the 16% of people who regularly used them for preparing their evening meal use the microwave  for several items in the meal, or the whole meals, people cannot use these basic models of microwaves, for example, to brown meat or bake potatoes. Even people with a microwave oven with a grill and convection oven often do not take advantage of what they have to offer. Are the instructions not clear enough?  Or is that it is difficult to change habits and move from the toaster and the conventional oven, even if you sacrifice the opportunity for power saving and lower energy bills. The majority of people probably view microwave ovens as a low-cost small appliance, similar to a toaster or kettle, but not part of the integral, key cooking appliances within design of the kitchen. They see them as an add-on item, and often do not put the microwave on the counter top, for easy and frequent use the kitchen . Why is this?  Why don’t we use microwave ovens more if we think they might lower household energy bills?

Energy efficient – but not energy rated

 Although microwave ovens are energy efficient, they are not yet energy rated. A number of studies show that switching from cooking using conventional methods to cooking using the microwave oven could reduce energy bills.   Your local council may well be one that is trying to persuade you to switch to microwave cooking to reduce your energy bills. They are not wrong. Using a microwave is a power saving option.  The level of savings from studies carried out is estimated to be in the region of 10%. But it is a complicated area. There is not yet enough publicly available and reliable data based on comparisons in energy used by traditional ovens and microwave ovens. There is no reliable data for energy used by gas ovens and no comparison available between hobs. Importantly, the outcome depends on how much is cooked and the appliances chosen. Whether you use a conventional oven or a microwave it is more efficient to cook more of the meal in that appliance. For example, one study found that cooking one portion of potatoes in potatoes in a conventional oven used 10 times the energy cooking the same amount of potatoes in a microwave oven. Cooking four portions in a conventional oven used 2.5 times the energy than if the same batch had been cooked in a microwave oven.  But the microwave still saved energy. Using the microwave as an integral part of your cooking is also important if you want lower energy bills.  Foods cooked in the microwave will save power, but if you only use your microwave for a few minutes day and leave touch control models on standby for the rest of time, that will account for about one quarter of the total energy used by those models and it could rise to half the total energy used in some microwave ovens.  So while they are power saving the way you use you microwave makes a difference to the amount by which you can lower your energy bill.

Energy saving test

 In general, we could reduce the carbon emission from our cooking by switching from electricity to gas ovens and hobs. However, ovens and hobs have a long lifespan, and it would take a long time to achieve the change. One drawback is that to date there is no confirmed test method to identify the most efficient models of gas ovens and hob or the most efficient hob types. However, there are some activities - using a microwave -  that could be adopted which can lead to lower levels of carbon emissions in domestic cooking. Tests to compare the energy used in cooking a range of standard food products using a traditional electric hob and oven and microwave oven methods demonstrated the energy saving properties of microwave ovens. The foods were selected on the basis that they were suitable for cooking in a microwave oven by microwave-only or combination  microwave and convection methods. The foods were cooked according to manufacturers’ instructions for the portion sizes and for the chosen cooking methods which included on the hob, in the oven or in the microwave oven, as appropriate. The tests revealed that microwave cooking was more energy efficient for nine of 11 foods tested.  

The results of energy saving tests comparing microwave ovens with traditional electric ovens and hobs

It is clear that there is the potential for energy savings if we change traditional cooking methods to cooking with a microwave oven.  To date the most reliable sources estimate that  if we transfer just 20% of our cooking from electric oven and hob to a microwave we would save 50% of the energy used to cook those foods – and that means a more energy efficient way of cooking a small part of the food we eat would save 10% of cooking energy overall.  All the food below was selected for cooking in a microwave oven and carried microwave instructions. Where appropriate – a range of portion sizes (one, two and four portions) were cooked simultaneously or successively (the energy saving range varies with number of portions and microwave function).  The conventional ovens in the study were all ‘A’ rate for energy.

Milk Up to 800 g cooked in 200 g portions in mugs in microwave vs a saucepan on hob - 25 - 50%

New potatoes cooked with little water in microwave vs more water, on hob - 70 - 75%

Frozen vegetables cooked with little water in microwave vs more water, on hob - 65%

Fresh salmon fillet cooked without water in microwave vs poached in water, on hob - 63 - 78%

Whole chicken cooked using convection and microwaves in a combination microwave oven vs electric oven - 23%

Baked potatoes cooked using convection and microwaves in a combination microwave oven and in a microwave only vs electric oven 21 – 61%

Lasagne cooked using microwave only vs electric oven - 40 - 81%

Indian ‘ready meal’ cooked using microwave only vs electric oven - 38 – 63%

Frozen ‘ready meal’ for one cooked using microwave only vs electric oven - 55 – 73%

Frozen pizza cooked using convection and microwaves - in a combination microwave oven vs electric oven 22%

Porridge and baked beans (both cooked in bowls in the microwave and saucepans on the hob) consumed the same energy or more in a microwave oven than the EU Energy Label A-rated medium electric oven or on a ceramic hob.

More research to establish maximum cost savings

To date the most reliable research estimates that by switching 20% of our cooking from electric ovens and hobs to microwaves we could save 10% of all the cooking energy we use.  The researchers calculated that transferring 20% of cooking from A rated electric hobs and ovens to the microwave oven saves 50% of the energy used to cook those foods, and concluded that overall switching 20% of your cooking will mean a 10% energy saving. However, because researchers don’t know enough about how we prefer to cook different foods, it is not possible to give accurate estimates of what the total savings might be.  Whether we use lids on saucepans for – say potatoes and frozen vegetables -  the kind of saucepan and the amount of liquid used all matter when assessing the capacity for power saving and for lower household energy bills. The studies do not include fan-oven use, so we don’t know whether owners pre-heat their fan oven and whether they reduce cooking times as a result. And there is as yet no confirmed test method to identify the most efficient models of gas ovens and hob, or the most energy efficient hob types. It is important to remember that keeping touch control models with digital clicks and displays on standby accounts for between 25% and 50% of the energy used by the microwave. And using the microwave effectively is also about food that is evenly cooked and tastes good. Cooking foods in the microwave in a more energy efficient way doesn’t necessarily mean using your microwave at its highest capacity – sometimes food needs to be cooked at lower temperatures than the 850W or 1000W offered by the most advanced models. So there needs to be more work on how we prefer to cook and how we use our traditional ovens and our microwaves. But it is clear that there is the potential for energy savings if we change changing traditional cooking methods to cooking with a microwave oven.

Making the microwave an even more popular choice

The microwave is one of the greatest inventions of the twentieth century. But we have not embraced it fully as a key cooking appliance. While more work needs to be done to measure energy use and calculate potential energy savings by transferring cooking from traditional methods to the microwave oven there are many other opportunities to help us as consumers get the most out of our microwave.  Take, for example, kitchen designers. The microwave is still thought of as an ‘add on’ – sometime a cumbersome on - to the kitchen counter top. It is, therefore, often not placed in a position where it will become an integral part of the cooking process. People often fear that is difficult to learn how to use a microwave – it’s easier to use the conventional oven and hob. Designers are already producing new models that respond to people’s concerns that the oven is too small, or the controls are difficult. Simple instructions on packaging, in cookbooks, in magazines and online would help a great deal – many people still feel that the instructions ‘look’ difficult.  Changing our perception of the value of microwave cooking presents another opportunity. To some people the microwave still feels ‘unnatural’ or only appropriate for fast food or convenience cooking.  But we know from changing attitudes to frozen foods, which are now recognised as healthy as freshly prepared ones or even more so. Whether it is power saving and lower household energy bills, good food, or an easy to use, energy efficient appliance in a well designed kitchen that is important to you, it is only a matter of time before manufacturers, chefs, television programmes, magazines, kitchen designers take the opportunity to help us as consumers to get the best out of microwave cooking.

Keeping microwave food nutritious

Microwaves are a form of radiofrequency electromagnetic energy – they are generated electronically and they do not cause food or the oven itself to become radioactive. Microwaves do not change the chemical components of in food. When microwaves penetrate food, they cause water molecules in the food to rotate. The rotation causes friction between the molecules and the result is a rapid rise in temperature. This is why the cooking time with microwave ovens is shorter than with conventional ovens. When you shut the microwave oven off, the microwaves disappear. All cooking methods – including conventional ovens, stove-top cooking and grilling for example - have some effect on the nutrients in food.  The effect is worse if you over-cook the food. Microwave cooking tends to be less harsh on nutrients than conventional cooking methods, because the cooking times are shorter and less water is used. To help preserve nutrients when microwaving food, use techniques that promote the even distribution of heat. This will help prevent the formation of "hot spots" where portions of the food could be over-cooked. Lower household energy bills seem impossible with the recent rises in both gas and electricity.  So it is more important than even to use kitchen equipment with energy saving features. Power saving is more important for families now than at any time in the last thirty years. Microwaves are not yet energy rated but the most reliable research so far shows that transferring just 20% of cooking to a microwave can save up to 50% of the energy used to cook those products in a conventional oven or on a conventional hob – and that means saving 10% in energy savings overall for cooking. And using a microwave oven can be an effective way to help you to preserve the nutrients in your food.

Keeping microwave food safe   

No matter which cooking method you use, however energy efficient, bacteria can multiply and cause illness.  The risk increases when foods are allowed to sit at temperatures in the "danger zone" between 4oo C (40o F to 140o F) for more than 2 hours. C and 60 

Many of the rules for handling food safely apply to all forms of cooking:

• Always chill raw food promptly.
• Clean your hands and kitchen surfaces often.
• Keep foods separate.
• Cook food thoroughly.
• If you use the microwave oven to defrost or partially cook food, be sure to refrigerate or finish cooking the food by some other method right away
• Take steps to ensure that the microwave oven heats food evenly and does not leave under heated areas (cold spots) where bacteria might multiply and cause food poisoning.

You can promote even heating in the microwave oven by:

• Cutting food into small pieces for uniform cooking
• Arranging items in a uniform manner
• Adding a liquid (such as water, juice or gravy) to solid foods
• Stopping part way through cooking to stir foods or rotate trays or containers
• Covering food with a microwave-safe lid or with microwave-safe plastic wrap to trap steam
• Following directions for "standing times". This helps ensure that heat is distributed uniformly, even after cooking.
• Using a food thermometer to check that your food has reached a safe internal temperature. Take the temperature at several locations, especially in the thickest area of the meat, to ensure that the food is cooked all the way through.