How we test steam irons

Watch our video to find out how a Best Buy iron or steam generator iron can make laundry days less of a chore. We reveal the lengths we go to find the best steam irons and steam generators to transform your pile of laundry.

At Which? our extensive, market-leading tests are designed to sort the outstanding steam irons and steam generator irons from the feeble models that will leave you with an aching arm and clothes that still have creases.

Our reviews answer all the most crucial questions about steam irons. 

• How quickly and easily does it smooth creased and crumpled fabric?
• Will the iron clog up with limescale?
• How durable is the soleplate?
• Is the iron easy to use?
• Should I buy it?

Video: how we test steam irons

How quickly and easily does it smooth creased and crumpled fabric?

The only way to see whether an iron is any good is to iron with it. So, we pit each model against a pile of creased and crumpled laundry.

We iron our way through a stack of cotton shirts, light cotton skirts and linen trousers until all of the creases are removed, rating how long it takes to finish the job and how easy it is to banish creases. We then run each iron across a range of fabrics on our automated ironing bench to see how good it is at busting creases with only a couple of passes of the soleplate.  

And the more steam an iron pumps out, the quicker and easier it will be to iron with. So when an iron arrives at our test lab, we also measure just how much steam it will produce for you at home. We’ve found that more powerful irons aren’t necessarily any steamier than low wattage models, and some premium steam irons that are billed as powerful steamers don’t always produce more steam than budget ones.

The best irons and steam generators power through creases in no time and leave clothes beautifully smooth. But the worst make ironing hard work, meaning you’ll have to press down hard and won't get all the creases out.

Don't miss our guides to choosing the best steam iron and finding the best steam generator iron.

Will the iron clog up with limescale?

Not many of us enjoy ironing, but you certainly don’t want your iron to start flagging before you do. So we test just how good an iron is at preventing limescale from forming and clogging up the system, which causes steam levels to fall.

To see how tough on limescale an iron is over time, we hook each one up on our custom-built rig where they steam continually for two hours, then rest for 40 minutes to cool down. We repeat this process over 48 hours - to simulate ironing for an hour a week for nearly a year – and measure the steam rate at various intervals.

Irons that are tough on limescale will be as steamy after 48 hours of testing as when brand new. Whereas steam consistently tails off on the worst models to practically non-existent levels – which will make ironing really hard work.

To see whether the iron’s cleaning function is any good, we descale the iron after 48 hours on our test rig, following the instructions in the manual. We then measure the steam rate for a final time.

The results of all these tests enable us to give each iron and steam generator iron we review a rating for limescale resistance and how easy it is to descale.

How durable is the iron's soleplate?

A scratched soleplate can cause the iron to snag and catch on fabrics. This makes ironing harder and can even cause delicate clothes to tear.

Many manufacturers claim their steam irons have extra-tough soleplates that won’t scratch if they catch on buttons or zips, or if you need to wipe them down vigorously. So to see how the claims stack up, we rub each soleplate 20 times with a scotch brite scouring pad (the sort you might use to clean your dishes with) to see whether the soleplate lives up to the claims.

Some soleplates are so tough our scouring pad has absolutely no effect. Others mark quickly and end up scratched beyond repair.

How easy is it to use?

Some irons and steam generators are much easier and more pleasant to use than others, so we carry out a number of tests and checks to see which models will help you to sail through the ironing and which will make the job harder than it needs to be.

We record how heavy each iron is when it’s full with water and measure the amount of water it will hold, which can sometimes differ from what the manufacturer claims. We also check the length of the power cord and rate how likely the cord is to get in your way while ironing.

Next, we time how long it takes for it to heat up and start producing steam, so you’ll know whether you’ll have to wait ages before you can iron your outfit in the mornings. We rate how easy the tank is to fill, how comfy the handle is to grip, how simple the descaling process is and how easy all of the buttons and dials are to use while ironing. We even rate how easy it is to store away when you’ve finished the job.

All this goes into our ease of use ratings, which are provided in each of our iron and iron and steam generator iron reviews.

Should I buy it?

Each of the assessments described above goes part way to making up the iron's total test score, which is the overall percentage score we award to each steam iron and generator. But certain assessments are more important than others and so carry different weights. Our overall ratings ignore the price and are based on:

• 50% ironing performance
• 20% ease of use
• 15% steam power 
• 15% limescale resistance

A steam iron needs to score 72% or more in our tough tests to qualify as one of our Best Buy steam irons. A steam generator must earn 80% or more to earn our Best Buy recommendation. Irons and steam generators that score 45% or less are highlighted in our reviews as Don't Buys.

Improvements to our tests

We constantly improve our iron and steam generator tests to ensure that only the very best models hit our Best Buy gold standard. This means that some of the older models we have reviews for on Which.co.uk (tested before August 2014) were tested in a slightly different way to how we currently test.

Although you can generally compare results for irons and steam generators tested before August 2014 with those tested after (the date tested is shown under the 'Technical specifications' page in each review), the results don’t directly correspond. However, each score still gives a very good indication of the overall performance of the steam iron.

How we've changed our tests since 2014

• The automated ironing bench and soleplate scratch tests were new additions to our irons testing in 2014, which means you won't find these star ratings on some reviews.
• For models tested before 2014, the total test score was largely based on the same factors as described above, but steam power wasn’t included and limescale resistance and ease of cleaning accounted for 30% of the score total.

What is a Which? Eco Buy steam iron?

If you want to make the most sustainable choice when next buying a steam iron, an Eco Buy is for you. 

Eco Buy steam irons last longer, and thus have a lower impact on the environment over their lifetimes than other steam irons.

We calculate this by looking at how reliable the steam iron's manufacturer is and how easy it is to maintain the iron, to get an idea of how long-lasting it’s likely to be. We also look at how scratch-resistant its soleplate is.

To become an Eco Buy, a steam iron must have:

• A total test score of at least 62% for regular steam irons, or 70% for steam generator type irons
• Four stars and above for cleaning efficiency
• Four stars and above for ease of cleaning
• Five stars for resistance to limescale
• Four stars and above for soleplate scratch resistance
• Its brand must get a good reliability rating in our annual steam iron owners survey

Only between 5-10% of steam irons are sustainable and effective enough to be Eco Buys. To find out which qualify, head to our steam iron reviews and use the Eco Buy filter.