How we test built-in ovens
We test 50 built-in ovens each year – single ovens, double ovens, electric and gas.
Read on or watch our video below to learn more about how our labs test to find the best.
Why our oven tests are different
Almost all free-to-access websites review ovens using an individual tester and generate scores based on that person’s preferences. Free sites also typically get ovens free of charge directly from manufacturers or their PR representatives.
As well as using multiple testers in a lab-based scenario, the Which? overall percentage score is calculated purely on the measurements and ratings supplied by the lab, meaning there is no room for unconscious bias when giving an overall rating. We also buy every single appliance we test, and do not accept free samples for any of our full lab tests.
What are Which? Best Buys and Don’t Buys?
Best Buys are given to ovens that impress the most in our tests. An oven that scores 74% or more is a Best Buy and comes with a firm overall recommendation, although you should still read our reviews to check for any weaknesses that might impact your buying decision. Meanwhile, ovens that score 45% or below are Don’t Buys.
- typically tick the most important boxes – they are quick to heat up, stick closely to the correct temperature and spread heat evenly throughout the whole oven cavity.
- Don't Buy ovens fall down in important areas – they may take an age to heat up, and even then veer far away from the temperature you think they are at.
How is the Which? score calculated?
The Which? overall score is a percentage. This score only takes into account the results of our tests and ignores price completely. This means that all ovens are tested on exactly the same scale, so you can compare any oven at any price and know how it measures up against its rivals in key areas. All ovens are tested in the same way, regardless of the manufacturers’ claims.
Weightings and star ratings
A Which? overall score is made up of dozens of individual tests and checks, from key factors such as speed of heating up, temperature accuracy and heat distribution to ease of use and what the grill is like. Behind each of those ratings could be more than 20 individual tests and checks. This means that the most important things – such as how accurately the oven maintains the correct temperature and distributes heat – will more greatly impact an oven’s score than whether or not the oven has loads of automatic programs.
To keep things simple, the most important scores are shown as star ratings out of five on each oven’s Test Results page as an easy-to-compare list of strengths and weaknesses, so you can quickly work out whether an oven is right for you.
How the overall oven test score is calculated
Our key testing criteria
Below are the key testing categories and how we evaluate each one:
Oven speed of heating up
Key question: How quickly will this oven heat up?
We set each oven to heat to high and low temperatures, and we record how long they take to reach these targets. Heat settings for conventional electric and gas ovens are 180°C (gas mark 4) and 200°C (gas mark 6). For fan-assisted electric ovens, the settings are 150°C and 180°C.
The best ovens take less than five minutes to heat up to 180°C, while the poorest ones will keep you waiting for nearly three times as long.Speed of heating up makes up 7% of the score for an oven.
Key question: Will this oven accurately remain at the correct temperature?
We record how accurately an oven sticks to the temperature it says it's at. Best Buys stay very close to the set temperatures, but the least accurate ovens can overheat by more than 30°C. This is enough to result in burnt food.Oven accuracy makes up 20% of the score for an oven.
Oven heat distribution
Key question: Will the heat spread evenly and consistently throughout the oven?
We use baking trays covered with strips of shortbread to reveal just how effective ovens are at spreading heat right around the oven. The colour of the shortbread after cooking shows how evenly the oven distributes heat across each oven tray. The best ovens we’ve tested deliver heat evenly across the shortbread, but the worst leave the middles unbrowned and the corners burnt.
We also bake a large sponge cake in each oven and measure how well and evenly the cake rises, and how evenly the cake is browned.Oven heat distribution and consistency makes up 20% of the score for an oven.
Key question: How effective is the grill part of this oven?
We cover each grill pan in white crustless bread to see how well, how far and how evenly the heat spreads. The best grills we’ve tested can effectively heat more than 90% of the grill pan.
The worst will struggle to heat anything more than the area directly beneath the element, or around 40%. This will leave you having to shuffle food around to get it evenly browned.Grill performance makes up 20% of the score for an oven.
Oven ease of use
Key questions: Is it easy to use the main features of this oven?
We use an independent panel to assess how easy each oven is to use. They look at how clear the markings are on the oven and how straightforward it is to operate the the various settings. They load and unload the oven and grill, and assess how easy it is to check up on food while it is cooking.Ease of use makes up 17% of the score for an oven.
Key questions: If the oven has a self-cleaning function, does it work well? If it doesn’t have one, how easy is it to keep clean manually?
Cleaning an oven is nobody’s favourite task. At the lab, our testers carefully apply cooking grime to various parts of the oven, then turn up the temperature and bake it on. They then run any self-clean function, such as pyrolytic cleaning, and see how good the results are. They also clean each oven manually, to find out which ones take the least effort to keep spick and span.Ease of cleaning makes up 8% of the score for an oven.
Smart oven testing
More and more kitchen appliances are wi-fi-enabled and can be controlled via an app on your smartphone or tablet. Modern ovens are no exception, so we’ve introduced new tests to help you know whether an oven you’re thinking of buying is safe and secure. We also assess whether the related app is of any real practical benefit.
Is the app useful?
We look at what cooking programs and settings on the oven are available via the app, and which aren’t. For example, are you able to adjust cooking temperature or cooking time? And can you turn your oven on or off remotely? We see if the app is intuitive to use, whether it’s logically laid out and whether the menus are easily accessible.
Are there any safety issues?
We see if an app allows you to do things that could lead to a physical safety risk. So far, our investigation reveals that most oven apps don’t allow you to do anything that could lead to problems.
Most apps allow you to turn on the oven while you’re out of the house. This could be a safety issue if it was allowed on an ad-hoc basis. But, rather like the delayed-start function on an oven, you need to set up the oven manually before you leave home.
We’ve found one app that allows the oven to come on while the door is open. We believe this is a potential safety issue, which we have raised with the manufacturer. This issue is highlighted in the relevant reviews. Fortunately, none that we’ve come across so far allow you to remotely activate the high-temperature pyrolytic cleaning program.
Are there any security issues?
If your oven app is not secure, it could provide hackers with a back door into your home wi-fi network. A poorly designed app could allow them to control your oven and other wi-fi-connected appliances in your kitchen, or gain access to your computer or tablet and hack into your personal accounts. We therefore put smart ovens through a privacy and security test programme. For each model we test, we confirm whether or not we would recommend use of the app on security grounds.
When you first set up the app and when you use it, data is passed between your phone and oven. Encryption is necessary to avoid your personal data being exposed in the process. We look at the encryption methods used, check that no personal data is being sent or received unencrypted, and we see which country the data is being sent to.
If the firmware in your oven is out of date or not maintained well, it could allow a hacker to access your device and data. We check for this in our security tests and highlight any issues we come across. We also check whether the manufacturer details the update policy across your product's lifetime.
Data transparency (permissions)
We check what data the app asks for when you set it up, on both Android and iOS devices. If any of the data requests seem unnecessary, we try to find out why it’s being requested.
A strong password is a fundamental part of digital life that most of us have become used to. But some apps still allow relatively weak passwords and leave your data vulnerable. We’ll highlight any we have concerns about and give advice on how to create the most secure passwords.
Most of us keep our ovens for many years. But what happens to your data linked to the oven if you decide to upgrade or move house? We check how easy it is to delete your account and all associated data. For example, can you completely delete your account yourself, or does it have to be via customer service?
This is a cyber version of eavesdropping that leaves your personal data vulnerable. A hacker accesses the information passing between your phone or tablet and your oven. We check each model for this vulnerability and highlight to the manufacturer anything of concern we uncover in our review.
Other types of attacks
We’ve listed the most common hacking threats, but new ones appear all the time. We keep on top of what’s new and update our testing so you can be confident that the smart oven you choose is secure.
Pick the perfect oven with Which? reviews
The actual usable capacity of your oven can be different from what the manufacturer claims. We only measure the space that you will actually be able to use inside an oven.
We measure the internal width from side to side, and the depth from the inside of the door to the back of the oven. But we only measure the height from the top of the lowest shelf to 3cm below the top of the oven. We don’t include the space beneath the lowest shelf, which manufacturers often do.