Choosing a heat pump tumble dryer over a vented or condenser dryer is a great way to reduce your energy bills – but only if you remember to clean your dryer’s lower filter.
Rinsing the sponge filter by the heat exchanger is a relatively simple, yet often overlooked task.
Our investigation shows that failing to clean the lower filter can result in longer drying times, steamier windows and, worst of all, mounting energy costs.
Read on to see just how much energy use can climb with a dirty filter, and how you can keep your dryer working efficiently.
Go straight to the best tumble dryers we’ve tested in our lab.
Our snapshot tumble dryer test
Which?, along with other European consumer organisations, tested eight representative heat pump tumble dryers – one from each of the major brands.
We ran each dryer for 20 cycles, ignoring any prompts to clean the lower filter.
For three brands, energy use was unaffected or even went down, whereas energy use increased by 50% for the Beko and Candy machines, and by 40% on the Samsung.
The results clearly show that to make the most of the amazing savings of heat pump dryers, you’ll have to clean the lower filter regularly.
It’s helpful to have a reminder on the machine so you don’t forget this crucial task.
Beko’s heat pump dryers typically have an ‘evaporator indicator’ that flashes when it needs doing, though this didn’t come on in the 20 cycles of our test.
Samsung dryers also have an indicator, or an audible signal every 25 cycles. However, you’ll need to clean more regularly than that, as the machine we tested was already using 30% more energy by its 18th run.
Candy dryers have a light that comes on after every cycle to remind you to clean both the lint and the lower filter.
What happens when you don’t clean the lower filter?
As well as mounting energy costs, we also saw an increase in drying times. The Beko and Candy dryers took 40% longer to dry the same load on cycle 20 than on the first run.
This means if your clothes usually take four hours to dry, you’ll have to wait an extra hour and a half before your load is ready.
We also found that the condenser works less efficiently – in fact 12-13% less efficiently for the Beko and Candy machines – when you don’t clean the lower filter.
This means more moisture leaking into your home, steaming up your windows or potentially even causing a damp problem.
What did the manufacturers say?
Samsung told us: ‘We always encourage our customers to clean their lint filter after every load, and their lower filter at least every month. Test results obtained by Which? do not match our internal test results’.
Beko said: ‘We don’t sell the tested model in the UK. Since we’re not familiar with the reviewed model we can’t comment on its performance’.
Candy said: ‘Which?’s tested model isn’t sold in the UK. All instruction manuals provide extensive guidance. Cleaning after every use helps to ensure continued efficient, effective and safe product performance’.
How to maintain your tumble dryer and clean the lower filter
You’ll find it in the bottom corner of your heat pump dryer, in front of the heat exchanger. You might need to push two small levers inwards to unlock it.
Once unlocked, remove the sponge filter. Pick out bits of fluff and hair from the exchanger and its casing.
Rinse the filter under a cold tap until the water runs clear. Wait until it’s completely dry before you put it back.
As well as cleaning the filter, you can also separate your fabrics by type and untangle your clothes to make your dryer run more efficiently.
See our top tips on how to clean and maintain your tumble dryer to find out more.