Microwaves

This guide covers microwaves, including combination microwave ovens which also have conventional heating methods built in.

We look into energy efficiency, mainly in comparison with other cooking methods, and question whether the potential energy savings are worth the costs of manufacture.

We also offer some advice on how best to dispose of your unwanted microwave, try to separate fact from fiction when it comes to health risks, and look at the issues related to microwave meals.

Buying an ethical and eco friendly microwave oven 

As with the other home appliances we have looked at like fridge/freezers and washing machines, some brands scored almost no points (out of 100).

Although the top-scoring brands don't get really high scores, there are definite differences in ethics if you are looking to buy a new or secondhand microwave.

In this guide to sustainable microwaves, we review the well-known brands like Bosch, Russell Hobbs and Zanussi, along with brands at both ends of the price range such as Cookworks (from Argos, owned by J Sainsbury), and Miele.

Microwave brands and connections with military equipment

It may come as a surprise that something like a microwave oven can be connected to the military. 

Eight brands on the table were marked down under the company ethos category rating for their links with the arms trade and military: Beko, Blomberg, Grundig (all owned by Koç Holding), Gorenje (owned by Hisense), Samsung, Sharp, and Siemens. Siemens is also subject to a boycott for its contracts in Israel.

• Koç builds tanks, armoured vehicles, and drones for the Turkish military via its wholly owned subsidiary Otokar.
• Hisense was named as a leading supplier of AI defence systems to the Chinese army, via its Shenzhen Zhongke Haixin Technology subsidiary, in a 2023 CSET report.
• Samsung also produces ‘Tactical Edition’ mobile devices, “designed to help transform the way military personnel operate”.
• Sharp's white goods in European markets are produced by the Turkey-based Vestel, under an exclusive licence. Vestel is part of Zorlu Holding, and Zorlu’s defence subsidiary Lentatek also produces aerial drones for the Turkish and Saudi militaries.
• Siemens provides ‘digital optimisation’ services to US Navy Shipyards.

While they weren’t marked down, Bosch claims that its parts were "misused" by the Russian military against Ukraine for its infantry vehicles. Bosch then suspended its business with Russia. Bosch also owns NEFF and Gaggenau.

Investor AB, which holds a 28% stake in AB Electrolux (AEG, Electrolux, Zanussi), also owns 40% of shares in Saab AB. Saab produces equipment for ground combat, submarines, and air ‘fighter systems’ for military defence.

The microwave technology that microwave ovens use was actually invented by the US defence firm Raytheon in the first place, while they were developing radar systems.

Conflict minerals in microwaves

Like most electronic devices, microwaves require conflict minerals, such as: tantalum, tin, tungsten, and gold. Several brands in this guide got a low score in the conflict minerals category. 

Five had no conflict mineral policy at all. These are:

• Amica (CDA)
• Glen Dimplex (Stoves)
• Hisense (Gorenje)
• Montpellier

Top scorers for their policies on conflict minerals included Samsung, followed by AB Electrolux (AEG, Electrolux, Zanussi) and Sainsbury’s (Cookworks).

Conflict minerals sourced from the Democratic Republic of Congo and surrounding countries are a major issue in the electrical industry. Profits from their sale have frequently been found to fund wars and arm militias. The mining practices are usually also very unsustainable, and forced and child labour is a common problem.

Read the separate article for more information about conflict minerals and home appliances. 

Is the cost of manufacture worth the savings in household energy?

Cooking is an area where choosing the most efficient methods may not significantly impact on the overall energy usage of a household. Across the EU, on average, cooking represents only about 6% of household electricity usage, compared to about 14% on lighting and electrical appliances, 15% on water heating and over 60% on heating.

Taking that into consideration means that, even if you can save energy by using a microwave for some cooking processes, it will not necessarily equal the energy and resources used to manufacture that microwave in the first place. A recent study suggested that the energy used to manufacture a microwave is about 494 kWh – a fifth of its total lifetime energy use – and manufacture has other environmental impacts as well.

Some microwaves come with a 10 year parts guarantee (usually only if registered with the manufacturer). Apparently the life expectancy of microwaves has dropped since the late 1990s, but this is mainly due to “faster product innovation cycles”, in other words, people are replacing them before they need to.

No energy labels on microwaves

Comparing energy efficiency between microwaves can also be a little tricky. Unlike many other household appliances, microwaves are not required to carry an energy label.

However, one tip is to either avoid getting a microwave with a digital clock or, if it does have one, make sure you turn the whole thing off in-between uses – unless, of course, you are using it as your clock! That will save a small amount of energy.

The UK should extend labelling laws to cover all products that consume energy in use.

Combination microwave ovens

A combination (combi) microwave oven may be an option if you have limited space and are looking to replace your oven. 

These are single units which contain both conventional and microwave heating mechanisms. This means that you can still get the energy-saving benefits of cooking with a microwave, without the extra impacts of manufacturing, transporting and disposing of a whole extra appliance.

How to make your microwave last longer

One way to prolong the life of your microwave is to keep it clean of food debris, which can otherwise cause rust inside. 

There are also certain foods that should only be microwaved with care, such as thick tomato sauces. Bubbles can build up and then burst, splattering the sauce everywhere. You can use short bursts of half power, stir it and keep a loose cover on the container. 

It’s also worth saying you should never use foil or other metal items in a microwave (including dishes with decorative metal finishes), as the electromagnetic waves can cause sparks which could damage the machine. 

Polystyrene containers are also a no-no, as they can melt and release harmful chemicals.

Eco ways to dispose of a microwave

How you dispose of an old microwave can have environmental significant impacts. 

If it's broken, the first thing would be to check if it can be repaired, either through the warranty, by an electrician or at a repair cafe. We have links to some repair cafe directories at the bottom of the Library of Things directory. 

If its not broken, you could sell it or give it away - local online marketplaces may be one place to start.

Researchers estimated that in 2005, 184,000 tonnes of waste electrical and electronic equipment (WEEE) was produced by discarded microwaves in the EU alone, and predicted this to rise to 195,000 tonnes by 2025. Electrical waste can cause harmful toxins to leak into the environment.

You can prevent an unrepairable microwave ending up in the landfill by using the Recycle Now website to find your nearest recycling centre that will accept it.

Or, under the Retailer Take-back scheme started in 2021, any large shop you buy electricals from must provide a ‘take-back’ service for your old equipment, where it is the company’s responsibility to dispose of it correctly (this applies to other household appliances and electrical items as well as microwaves). Currys, B&Q and John Lewis will take back all electricals without you even buying a replacement.

Microwave meal packaging

The microwave ovens themselves are not the only issue to think about. With the microwave came the microwave meal, packaged in a plastic tray with a plastic film. Not all local authorities collect these plastic trays. Where they do, black plastic trays make it difficult for sensors at recycling plants to pick out the containers against the backdrop of a conveyor belt. This leads to a high proportion of black containers being mistakenly sent to landfill from the recycling plant.

Some companies have started to develop ‘compostable’ alternatives to plastic microwave containers – these are designed to be recycled with food waste.

We look at plastics and the problems and solutions in a separate article. 

Microwave health and safety issues

There is a lot of opposing information out there relating to the effect of microwaves and microwaved food on our health. Product recalls tend to have been around faulty components causing a fire hazard or risk of electric shocks, not dissimilar to the dangers of other household appliances.

Nutrients and carcinogens

Some studies have found that microwaving starchy foods causes acrylamide, a carcinogenic chemical, to form in the food. However, this is also true of baking and frying starchy foods. Studies offer opposing results about whether microwaves are a more dangerous or safer option than frying.  Boiling is considered the safest method of cooking starchy foods to avoid high levels of acrylamide formation.

The situation is similar when it comes to looking at whether microwaves destroy nutrients in food. It is true that food will lose some nutrients when cooked in a microwave. However, this is equally true of traditional cooking methods. The effect can also vary between different nutrients. 

Radiation

Some people worry that microwaving food can cause it to become radioactive, or that using microwaves can expose you to harmful radiation. Microwaves are a low-energy form of radiation and work by emitting enough energy to cause water molecules in the food to move. This movement then causes friction which, in turn, produces heat.

Microwaves are a form of non-ionising radiation. Microwaves are not strong enough to remove electrons, which is what is required for substances or objects to become radioactive.

This also means they do not have the energy to alter cells in the same way that more powerful forms of radiation do. While overexposure to non-ionising radiation can be damaging, causing problems such as burns, it will not damage your cells and DNA in a way that will cause them to become cancerous. Microwave ovens are designed to contain the microwaves within the oven, so over-exposure would only be likely if you were inside the microwave!

When it comes to microwaves, as with other appliances, there is probably a greater risk of harm from either fire or electric shock. As long as your microwave is not damaged it should be safe to use.