Are new electric clothes dryers more efficient than older models?
What ENERGY STAR dryers are available to replace an old electric dryer? I’ve looked for efficiency information on electric clothes dryers but can’t find any. I have an electric clothes dryer that’s over 10 years old and I’ve been thinking of replacing it with a more energy efficient model, but I can’t find any from any of the big name brands. Are newer electric clothes dryers more efficient than something 10 or more years old?
Answer from Green Energy Efficient Homes
Until recently (ie. before January 2017), you would not have found ENERGY STAR dryers on the market, because fossil gas dryers are not covered by ENERGY STAR standards, and because for electric resistance-based dryers, there should not be any significant difference in efficiency between older and newer electric clothes dryers. Beginning in 2017, however, new heat pump electric dryers began to appear on the North American market, and these are significantly more efficient than resistsance-based dryers, and many have therefore earned ENERGY STAR certification. More on that a little later.
Most electric clothes dryers use an electric resistance heating element, which is always 100% efficient at converting electricity into heat. By far the biggest share of energy used by an electric dryer is for the heat, so improvements to the fan motor won’t make much difference in dryer efficiency. Fan motors are inductive loads, which means you can actually improve the power factor efficiency of them by using a built-in capacitor in the motor assembly, but assuming this makes the motor 5-10% more efficient it will only effect the overall efficiency of the dryer by 0.5 to 1%.
ENERGY STAR dryers would need to be at least 10% more efficient than the current minimum efficiency standard for electric clothes dryers, as typically the ENERGY STAR standard for an appliance type starts with what is easily achievable with current technology, and tries to push for a higher efficiency. But there’s really not much you can do to make an electric resistance dryer more efficient, so I don’t think you’ll ever see ENERGY STAR dryers being certified among the resistance-based dryers, because there would be no way for manufacturers to improve on existing efficiency, and therefore no point in ENERGY STAR setting a new standard.
To give an example of how hard it is to boost dryer efficiency, consider this: The Canadian Office of Energy Efficiency at one time provided dryer ratings that varied only between 950 kWh/year (least efficient) and 898 kWh/year (most efficient), which is only a difference of 52 kWh a year, or about $5-10 worth of electricity depending on what you pay. Compare that to washing machines, where the differences between lowest and highest energy use washers ranged (at that time) from 100 to 500 kWh per year. That means the most efficient washer then was 400% more efficient than the least efficient. That’s why there are plenty of ENERGY STAR washers and no ENERGY STAR dryers for resistance-based heating.
Heat pump dryers
Enter the heat pump dryer. Heat pump dryers have been a thing in Europe and Asia for over a decade, and are just starting to appear in North America. I purchased one in 2020 and have been quite happy with it. A heat pump dryer achieves greater heat output, for the same amount of energy, than a resistance-based electric dryer, which remember, is 100% efficient at converting electricity to heat. How is this possible, you ask? Because a heat pump does not create heat, it moves heat from a cooler place to a warmer place. This is what your refrigerator does – moves heat from the cool refrigerator to your warm house, which is why you feel heat coming out the top, sides, or bottom of your fridege when it’s running. An air conditioner does the same. Both of these are examples of heat pumps. Another example is a whole house heat pump, which extracts heat from the cool outdoor air and uses it to heat your home.
A heat pump dryer works on a somewhat similar principle. It runs a heat pump that draws cool air from your house, extracts heat from it, and uses that heat to dry your clothes. On the cold side of the cycle, before it ejects the cold air back into your house, it uses the cold to condense moisture out of the air, so that moisture can go down the drain. This improves the efficiency of heat pump dryers in two ways: First, unlike with a gas or electric dryer, you are not venting any air out of doors, so you don’t such your heated or air condtioned air out the vent and draw in cold (or hot) outdoor air into the house to replace it, requiring more heating or cooling; and second, the heat pump can produce several units of heat energy for each unit of electrical energy. This ratio is called the Coefficient of Performance or COP. The COP of an electric resistance dryer is always 1.0 or later (it’s the same thing as saying 100% efficient, in that case); there is no way to produce more heat energy than the electrical energy input, in the case of an electric resitsance dryer. For an electric heat pump dryer, the COP can be at 2.0, or 3.0, or even 4.0 or higher (in theory at least).
These ENERGY STAR dryers, which are all heat pump based, achieve significantly better performance than resistance heat dryers. For example, out of 366 electric resistance dryers listed on the ENERGY STAR website, the lowest rated non-heat-pump dryer is rated at 236 kWh/year, while the lowest rated heat-pump dryer is rated at 125 kWh/year, or almost twice as efficient.
Other ways to save on drying
The best way to save energy on drying your clothes is to upgrade your washer to a front-loading, ENERGY STAR rated washer. Front loaders use less water and less electricity to wash, but above all they spin much faster than top-loaders so they extract far more water than a top loader could. As a result, the clothes you put into the dryer from a front-loader are much dryer to start with than those from a top-loader, so take much less energy to dry.
Of course, even better are clothes lines and clothes racks. We have a dryer but almost never use it, except for towels, which get to feel like prickly boards when you dry them on the line, and some permapress or cotton shirts that get too wrinkled when line dried.
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