A heat pump tumble dryersitting on a wooden floor with a blue wall behind it.

Your typical vented tumble dryer uses a lot of energy, which is why many people are looking for alternatives.

A heat pump tumble dryer is one alternative that is becoming more popular.

But how does a heat pump tumble dryer work?

A heat pump tumble dryer works by continually recycling air in a closed system. A heating element warms the air, and a fan circulates it around the clothes. The air then passes through an evaporator, where the moisture is removed and condensed before the air is reheated and recirculated.

Drying clothes doesn’t have to be a chore – in fact, with the help of a heat pump tumble dryer, it can feel like a breeze.

Keep reading for a detailed explanation of the tech and science behind this technology and how it compares to the regular dryer technology we’re all used to.

A Heat Pump Tumble Dryer Uses a Closed-Loop System

illustration of technology behind heat pump dryers in relation to conventional dryers
Heat pump dryers use a refrigeration cycle to recover heat from within the drum, concentrate it and reuse it to heat the air before it is blown back into the drum to dry the clothes. This makes them much more efficient than conventional dryers that vent the heat from the drum and lose it to the room or vent it outside.

To understand the science behind a heat pump tumble dryer, you first need to understand the concept of closed-loop systems.

In the context of a tumble dryer, a closed-loop system means that the warm air used inside the device gets recycled and is never vented into the atmosphere.

Because of that, there’s no need to constantly heat new air, as the same air can be used repeatedly.

The main advantage of this is that it uses less energy than an open-loop system (like a vented tumble dryer) because less energy is needed to heat the air.

In a vented tumble dryer, the appliance uses hot air to absorb moisture from clothes tumbling in the dryer drum. The hot air is passed through the drum and then vented outside.

The problem with this system is that the hot air is constantly being vented out, so the dryer must work hard to heat new air to blow through the drum.

To better understand how the closed-loop heat-exchange system works, here’s a rundown of the critical stages a heat pump tumble dryer goes through during a drying cycle.

The Dryer Uses Hot Air To Absorb Moisture

A heat pump tumble dryer works by heating the air inside it using a compressor and a coil. The hot air is then passed through the dryer drum, which absorbs moisture from the clothes.

When the air is heated, its capacity to hold moisture increases. So, by heating the air, the dryer makes it easier for the air to absorb moisture.

The hot air heats the wet clothes and encourages the water absorbed in them to evaporate. As the hot air passes through the drum, it picks up the moisture that evaporates from the wet clothes.

The result of these processes is that the clothes in the drum dry out.

The Air Goes Through the Evaporator

After the air has passed through the drum, it goes through the evaporator. That’s a vital component of a dryer, as it’s responsible for cooling the air and condensing the moisture from the dryer.

The evaporator consists of a coil filled with low-temperature refrigerant, which helps lower the temperature of the air and extract moisture. As a result, the air that comes out of the evaporator is cooler and drier.

The Condensed Water Is Collected and Stored in a Tank

Illustration of a condenser dryer showing how it functions
Some heat pump tumble dryers collect the condensed water removed from the wet clothes in a reservoir that must be periodically emptied. Other models allow a drain hose to be connected to a drain in your home, which is much more convenient.

Once the air has been cooled and its moisture extracted, the condensed water is collected in a tank.

The tank must be emptied periodically; otherwise, the dryer will automatically switch off to avoid flooding the unit and spilling water out onto the floor of your home.

Some models have a drain hose that can be connected to a suitable drain in your home so that the condensed water is continuously discharged without the need for emptying a condensate reservoir.

The Collected Air Is Reheated

Once the air passes through the evaporator, it’s reheated using the dryer’s heat pump. The reheated air is then passed through the dryer drum to absorb more moisture from the clothes.

The process is repeated until the clothes are dry. And because the air is continuously recycled, there’s no need to constantly heat new air, making the dryer more energy-efficient.

Key Takeaway: As long as the dryer is turned on, the closed-loop system will continue to recycle the air, reheating it as needed using heat recovered from the drum exhaust air.

That means a heat pump tumble dryer uses much less energy than a vented tumble dryer, where no heat recovery occurs.

Differences Between Vented and Heat Pump Dryers

Having looked at how a heat pump tumble dryer works, let’s now compare it to a vented tumble dryer.

A Heat Pump Dryer Reuses the Same Air

Closeup side angle view of the top front of two heat pump dryers side-by-side
Heat pump tumble dryers recirculate the same air, recovering heat from the air that leaves the drum. This makes them far more efficient than vented dryers, which lose all the heat from the drum exhaust air.

The most significant difference between the two types of dryers is how they deal with hot air.

As mentioned, a heat pump tumble dryer uses a closed-loop system where the air is continuously recycled. That means the same air is used over and over again, which makes the dryer more efficient.

On the other hand, a vented tumble dryer vents the hot air out of the dryer and replaces it with new, cold air. That makes the dryer less energy-efficient because it must heat the fresh air constantly.

Heat Pump Dryers Operate at a Lower Temperature

Another difference between heat pump dryers and vented dryers is the operating temperature.

A heat pump dryer operates at a lower temperature than a vented dryer. That’s because the heat pump system works most efficiently at slightly lower temperatures.

On the other hand, a vented dryer tends to be hotter because it heats the new, cold air using an electrical heating element that operates at higher temperatures.

Heat Pump Dryers Protect Your Laundry Better

A closeup of the washing instructions label on a brown garment. The label has a red cross over the tumble dryer icon to indicate that it is not suitable for tumble drying.
Some garments will be damaged by the high temperatures in a tumble dryer. You should always follow the washing instructions on the label to avoid damage to your clothes.

Another benefit of heat pump dryers is that they protect your laundry better.

Since the air isn’t as hot, there’s less risk of damaging your clothes with too much heat.

Moreover, the lower operating temperature also reduces the risk of shrinking and fading.

On the other hand, vented dryers operate at a higher temperature, which can damage delicate fabrics.

Heat Pump Dryers Are Slower Than Vented Dryers

One downside of heat pump dryers is that they’re slower than vented dryers. Since the air is at a lower temperature, it takes longer for the clothes to dry.

However, the slower drying time is offset by the fact that heat pump dryers are more energy-efficient. So, you’ll save money on your energy bills in the long run.

Heat Pump Dryers Are More Expensive Upfront

A picture showing US Dollar bills floating around in a tumble dryer drum.
Heat pump tumble dryers can cost a lot more upfront than conventional vented or condenser tumble dryers.

Another downside of heat pump dryers is that they’re more expensive upfront. However, the extra cost is quickly offset by the savings you’ll see on your energy bills.

On the other hand, vented dryers are less expensive upfront but are not as energy-efficient so you may spend more in the long run.

The Bottom Line: Heat pump dryers are more energy-efficient than vented dryers. They’re also more expensive upfront. However, the extra cost is quickly offset by the savings you’ll see on your energy bills.

If you’re wondering whether a heat pump tumble dryer is more efficient than a condenser tumble dryer, too, we’ve got the answer for you in our article, “Is a Condenser or a Heat Pump Dryer More Energy Efficient?

Tips for Choosing a Heat Pump Tumble Dryer

Now that you know the difference between heat pump and vented dryers let’s look at some tips for choosing the right tumble dryer.

  • Consider the efficiency rating. Be sure to pay attention to the efficiency rating. The higher the rating, the more energy-efficient the dryer will be.
  • Choose the right size. Make sure to choose a dryer that’s big enough for your needs. Otherwise, you’ll end up using more energy to dry your clothes.
  • Check the features. Check the features and see if they’re right for you. Some features, like automatic shut-off, can help you save energy.
  • Take advantage of discounts. Many utility companies offer discounts on energy-efficient appliances. So, be sure to take advantage of them.
  • Check for Energy Star approval. When in doubt, choose an Energy Star-certified dryer. That way, you’ll know that you’re getting an energy-efficient appliance.
  • Check the warranty: Be sure to check the warranty before you buy. That way, you’ll be covered in case anything goes wrong. For the best protection, choose a dryer with an extended warranty.

For an in-depth review of some of the best heat pump dryers on the market, you can watch the following video:

A thumbnail of a video that shows the results of testing heat pump tumble dryers. There is a row of dryers with the title, "Test 3" written above.
This video gives a thorough lowdown on the pros and cons of some of the leading heat pump tumble dryers available.

Final Thoughts

A heat pump tumble dryer uses a closed-loop system where the air is continuously recycled.

The dryer passes hot air through the drum, which transfers the heat to the damp clothes and removes the moisture from them.

After that, the air passes through an evaporator, where the moisture is removed.

Finally, the air is reheated and passed through the drum and the clothes again.

Incorporating highly efficient heat pump technology into these machines, instead of traditional electrical heating elements, is a key factor in making them so efficient.

The other main reason they are so efficient is that heat is recovered from the air leaving the drum, which is much more energy-efficient than vented tumble dryers that lose all of that heat via the exhaust air vent.

Wondering how much energy a condenser tumble dryer uses? You can find out by reading our article here.

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