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How we test coffee machines

By Yvette Fletcher

Discover how we separate the shoddy coffee machines that produce weak espressos from the Best Buys that will deliver a heavenly caffeine fix.

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In our years of testing coffee machines, we found that spending more doesn't always guarantee a great coffee when you get home. In fact, we've tested some models that cost less than £100 and make better espresso than others costing more than £500.

We've made more than 1,700 espressos in our coffee making tests, uncovering some brilliant models that are quick, user-friendly and (most importantly) able to make superb espresso. But some coffee machines we've tested make espresso that's lukewarm and uninspiring, while others will leave you scratching your head due to unnecessary complications. 

Each coffee machine that passes through the Which? test lab is assessed using a stringent set of criteria to ensure that each of our reviews answer the crucial questions you have about espresso coffee machines, including:

Head straight to our coffee machine reviews to find the best model for you – or read on to learn more about how we test to answer each of these questions.

How well does the coffee machine make espresso? 

Giles Hilton, coffee-tasting expert and a member of the Speciality Coffee Association of Europe, acts as our expert taster for all the coffee machines we test. Giles' expertise means he can tell the difference between the espresso produced by different models using the same coffee, and how well the coffee machines we test extract the coffee. 

During our blind taste test, the most important part of our coffee machine testing, he gives us his verdict on the espressos and cappuccinos made by each machine. Taste is a big part of this test, but we also ask him to judge the appearance of the coffee, including its all-important crema, as well as the texture and aroma.

In our labs, we also test the temperature of the coffee made – we make an espresso, then insert a digital thermometer into the centre of the cup. We're looking for an average temperature no cooler than 60°C and no hotter than 88°C. We use the cup warmers on the machines that have them, but a warmed cup doesn't necessarily guarantee a hotter coffee.

You can find out more about what Giles looks for in a coffee in the video below.

How well does it froth milk? 

If a coffee machine offers some way for you to make milky drinks - whether it's a steam pipe, automatic milk frother or milk capsule - we test how well it works. It doesn't matter whether your favourite is a cappuccino, flat white or any of the latest fads – you'll be able to use our milk-frothing rating to find how easy it is to achieve perfect results.

We time how long it takes for the milk to be heated to 70°C, and how well the frothed milk combines with espresso to make a cappuccino. Our coffee expert Giles Hilton then rates the appearance and flavour of the frothed milk - and how well it combines with espresso to make cappuccino.

Does it work quickly? 

A good coffee machine will take up to 30 seconds to make a standard 30ml espresso and stop dripping. Poor coffee machines can take more than 30 seconds to make your espresso, and a further 30 seconds or more before they stop dripping completely, leaving you waiting longer for your drink. 

30 secondsThe maximum amount of time a good machine will take to make a standard espresso and stop dripping.

We time how long you have to wait for a standard 30ml espresso, and how long the machine continues to drip for afterwards so you won't have to hang about getting your morning coffee - or clearing up the mess.

How easy is it to set up and use? 

Some coffee machines are a cinch to use while others are unnecessarily complicated – and it's tricky to know which is which before you get them home. We rate each coffee machine for ease-of-use to ensure you don't end up with a horror. 

We check how easy the instructions are to understand and follow, how clear the controls and indicators are, whether the water tank is easy to fill and empty, and how easy the machine is to clean. We also check how straightforward it is to make a coffee, whether using capsules, beans or ground coffee. 

Is the coffee machine noisy? 

After feedback from Which? members asking about the quietest coffee machines, we've now added a decibel noise assessment into our test programme, just like we do in our kettle reviews. We check how loud each coffee machine is when making espresso and frothing milk and we also check how loud bean-to-cup machines are during grinding.

Should I buy it? 

Each of the assessments described above goes part way to making up a total test score, which is the overall percentage figure we award to each machine. 

We weigh the importance of each aspect based on what is most important to you, so for coffee machines we think it's essential that they do their core job of making an excellent espresso. However, we also ensure that models which are a faff to use - or horribly noisy - are marked down, so your morning coffee routine isn't a time-consuming nightmare.

Our total test score for coffee machines ignores price and is made up of the following factors:

  • 50% taste test
  • 25% performance
  • 20% ease of use
  • 5% noise

While ultimately you just want the best coffee maker, we've found that the different types have their own overall pros and cons. Capsule machines, for example, are usually very simple to use and this can bump up their scores. To account for this, we have a different cut-off point for each type of coffee machine, so you can easily find the best bean-to-cup, capsule or ground coffee machine - or use the percentage scores to find the best machine overall.

The percentage scores each type of machine needs to get to achieve a Best Buy are:

  • Bean-to-cup coffee machines -70%
  • Ground coffee machines - 72%
  • Capsule coffee machines - 77% 

Any machine that scores less than 45% is a Don't Buy. This means the machine is so poor at its core job of making espresso, or has another serious flaw, that we don't recommend you buy it.

If you aren't sure what type of coffee machine would suit you, use our guide to choosing the best coffee machine.

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