Do Washing Machines Heat Water? Here’s How They Work

When you throw in some white towels and set your washing machine to 90 °C, is it necessary to have your building’s water heater or boiler working away? Or does the machine heat the water itself?

If you’re having trouble with your washing machine at home, or you’re just curious about how they work, you might be looking for an answer to this question, and perhaps a way to identify and fix certain issues.

Before we go into more detail on the topic, here is a brief summary:

All modern washing machines take in cold water at the beginning of a cycle and have an internal heater that brings it up to the desired temperature. While some older and top-loading models draw hot water from elsewhere in the building. To be absolutely sure, consult the manufacturer’s user manual.

By the end of this article, you will be able to identify whether your washing machine heats its own water. You’ll also know where to begin when it comes to troubleshooting issues with your washer and hot washes.

If you’d rather not have to worry about all this, consider taking a look at our Homeforce Plumbing and Heating Plan. Our qualified engineers will be on hand to solve any problems that may arise with your washing machine and other appliances.

Does my washing machine heat water itself?

If you search online for this question, you’ll find conflicting answers. Some sources say washing machines have an internal water heater, while others say they have separate hot and cold water inlets.

It’s actually much more energy-efficient for the washer to heat the water itself, so it’s easier on both the planet and your wallet!

Additionally, washers that have an internal heater can even give better wash results due to the way the enzymes in the detergent work with lower starting temperatures.

According to the Centre for Sustainable Energy,

Modern washing machines, dishwashers and electric showers take cold water and heat it themselves so you don’t need a supply of hot water waiting for them in the tank.

But what constitutes a “modern” washing machine? And how can I determine whether my appliance falls into this category?

Which washing machines heat their own water?

At a glance, you can often figure out whether a washing machine heats its own water just by looking at which side the door is located.

Do washing machines heat water? … While it’s not a hard and fast rule, generally speaking, front-loaded machines tend to heat their own water, while (the rarer) top-loading machines draw hot water externally (i.e. from the building’s hot water supply).

Short of taking the appliance to pieces, it’s more sensible to refer to your owner’s manual.

They often have a diagram near the front showing all the components and connections. Scanning through the documentation, it will become clear whether it heats its own water or requires a hot water input.

It is wise to refer to the “troubleshooting” section of your manual whenever you have an issue with your appliance. More often than not, you will find the solution to (or at least an explanation for) your problem there.

If you lost the copy of the manual that came with your appliance, don’t worry. You can always download a digital copy of it from the manufacturer’s website, where you simply enter the model number and receive a free PDF download.

Will a washing machine work without hot water?

In the absence of a hot water supply or working internal heater, you might be asking yourself if your washing machine will function at all.

As long as the machine has a supply of cold water, then you can safely run it on a cold wash and see results. However, running the machine with no water supply whatsoever may result in damage to the appliance, so this should be avoided.

If your washing machine does not have an internal heater and tries to pull hot water from your home’s water heater, but receives only cold water, then it will simply run the programme with that cold water. Therefore it’s just like running it on a cold wash.

Will my clothes wash properly in cold water?

If your washing machine’s heater is not working, you might be tempted to just throw your clothes in the washer and run it on a cold wash. But will it work effectively? What kinds of laundry are better when washed cold?

Again quoting the Centre for Sustainable Energy

Most washing powders are now designed to work just as well at 30 °C as they do at higher temperatures. If you are trying to remove a particularly stubborn stain try using a pre-wash stain remover.

Even if your cold wash is as low as room temperature, below 30 °C, you are still likely to see good results for most items of clothing.

Cold wash cycles of 20 or 30 °C are great for freshening up lightly soiled garments and are easy on delicate fabrics.

The following categories of laundry, on the other hand, are best washed with warm or hot water:

• White clothes
• Non-delicate underwear
• Towels of all sizes
• Bed linen
• Stained and heavily soiled clothes

Also keep in mind that running the machine on a 20 °C wash too often can increase the build-up of mould and grease in the machine, particularly around the door seal and detergent drawer. This is usually accompanied by a not so pleasant odour as well.

Troubleshooting your washer’s internal heater

There are a few potential points of failure which can be the cause of your washing machine not heating its own water properly:

• A damaged control board
• Temperature sensors not working normally
• Damaged or loose internal wiring
• Faulty or damaged internal heater

If you are certain you have set the programme to a warm or hot wash, but your clothes are still coming out cold, then you can be fairly certain one of the above things is the cause of the issue.

You will probably not be able to tell if the water is warmed up by placing your hand on the door, and it’s well insulated and the water is only warmed up for a fraction of the overall programme.

You would need to do more research to find out how to further troubleshoot and repair the machine, or whether it makes more sense financially to just replace it.

Either that or you can call in a professional who will be able to tell you exactly what the problem is and how best to solve it.

If your machine is still covered by warranty, then contact the manufacturer before attempting a DIY fix as taking the machine to bits will void that warranty straight away!

More help with washing machine issues

We hope this article has been a helpful resource to help you understand your washing machine and what could be the matter with it.

One final tip – if you know someone is on their way to fix your machine or water heater, make sure not to start a cold wash too soon before their arrival as they will no doubt need to disconnect the water supply as part of the repair process, which would interrupt your wash cycle!

With our Homeforce Plumbing and Heating Plan, you can avoid all the stress and anxiety of unexpected breakdowns and costly repairs.

We have an expert UK-wide network of engineers who will be on hand to solve any problems that may arise with your washing machine and other appliances, with no further costs whatsoever outside of your monthly plan fee.

We have over 10 years of experience protecting UK homes against unexpected faults, breakdowns and other costly repairs. Get in touch today and talk to our friendly customer care team who understand that your home is more important than ever.