How We Test Laundry

See How We Test Other Products: Laundry tests washing machines and clothes dryers using a rigorous scientific methodology, developed through industry standards and internal research. This allows us to determine the performance of a washer or dryer in detail, and to use scientific data to discuss the pros and cons of a product.

We take thousands of measurements over a long period of time and analyze these results using a number of sophisticated mathematical techniques. Our testing is based on industry standards created by industry bodies such as the American Society for Testing and Manufacture (ASTM), the Association of Home Appliance Manufactures (AHAM), and the International Electrotechnical Commission (IEC), all of which allows us to really understand how washers and dryers perform.

Instrumentation & Data Analysis

To test the performance of washing machines and dryers, we measure temperature, power use, and other performance factors.

We use iButton sensors to measure the temperature of the water inside a washing machine and of the air used to dry clothes. We place the sensors inside waterproof containers and deposit them into a standard load of laundry. These small sensors log the temperature every two minutes for an entire wash or dry cycle, allowing us to measure the temperature inside the appliance without opening the door. These sensors can measure the temperature with an accuracy of .0625°C within a temperature range of 0°C to 85°C, and each sensor can hold over 8000 measurements. We then save the data for further analysis.

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The temperature sensors are placed in waterproof containers

To measure the water use of washing machines, we use a pair of water meters designed for hot and cold water. These are accurate down to 0.01 gallons. The electricity use of washing machines is measured using a Kill-A-Watt EZ power meter.

We quantify stain removal by taking color readings on each patch of a stain strip (more on those later). Color readings are measured using an X-Rite i1 Basic Pro 2 spectrophotometer.

Testing Conditions

Our tests are carried out in a custom-built, climate-controlled test facility, where we regulate both the temperature and the humidity. This ensures that tests carried out at different times take place under the same test conditions, with minimal variations in temperature and humidity. The washers are run on individually fused electric circuits, and are supplied water by a standard domestic sized water line. The hot water is heated to 130°F by a high capacity water heater, and then moderated to 120°F (which is about the normal temperature of water from a hot water heater in a home) by Intellifaucets, which add precise amounts of hot and cold water to achieve and maintain specific water temperatures.

Test Materials

Stain Strips – To test the cleaning performance of washing machines, we use cotton test strips that include a control swatch (a white patch) and 5 different stains: simulated sebum (human sweat), carbon black (a mix of carbon and oil), pig blood, cocoa and red wine. All of these stains have been evenly applied and are allowed to fully dry.

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The test strips used to evaluate washer performance

Wear & Tear Sheets – To test the amount of clothes wear that a washing machine causes, we use mechanical action test sheets made of cotton. Each sheet has a number of carefully cut holes that expose the cotton threads. We measure the number of threads that become dislodged during a wash cycle. Each sheet is used for one single test, and is not reused.

Detergent – To ensure a level playing field between washers and across wash temperatures, we use a standard detergent, known as AHAM HLW-2010 Formula III. This avoids any possible bias from detergents that favor or work better with a certain temperature or type of washer.

Wash Loads – We use a number of different laundry loads in our washing machine testing, depending on the type of machine (top load vs. front load) and the specific wash cycle. Cycle loads are composed of varying amounts of cotton towels, sheets, and pillowcases. We log the number of times these items have been used, and regularly replace them to avoid any issues with them becoming overly worn.

For most wash cycles, we use an 8 lb. (dry weight) load. For the Quick cycle, which was designed to wash a smaller number of clothes more quickly, we use a 4 lb. (dry weight) load.

Washing Machine Objective Testing

Cleaning Performance

To test the cleaning performance of a washer, we use the stain strips described above. Three of these stain strips are attached to towels that are placed in the washer with our test load. The items in the test load and the strips are put into the washer in an order that matches AHAM standards.

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One of our test strips, attached to a towel as part of a 4lb load

After the wash cycle is complete, the strips are allowed to dry flat, away from all light sources. Once they are completely dry, we measure the color of the strip in the XYZ color space. Each stain is measured in 3 locations, and the results are averaged.

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A test strip before (top) and after (bottom) washing

The scoring for this test is based on the amount of difference in the Y color (that is, luminance) value between the pre- and post-wash strip. The bigger this difference, the more the stain has been successfully removed, and the better the washing machine. The overall score is based on the average cleaning performance for each of the 5 stains across four standard wash cycles: Normal, Delicate, Heavy Duty, and Quick.

Wear & Tear Test

To test the wear and tear that washing involves, we used multiple standard mechanical action test sheets that are inserted into the wash. After the wash cycle is complete, these are carefully removed and allowed to dry flat. We then closely examine the sheets to see how many of the cotton threads have become loose. All of the holes in the sheets are examined (there are 5 holes per sheet), and multiple sheets per wash cycle are used.

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A fabric wear test sheet before washing (bottom) and after washing (top)

The scoring for this test is based upon the number of threads that have been loosened. The more loose threads, the more wear and tear there is on the test load and the lower the score. The final score for wear and tear is only based on the results from the Delicates and Normal cycle, as these are the two cycles where the preservation of your clothes is most vital.

Water Retention

To measure how much water remains in the test load after it is washed, we measure the bone-dry weight of the load before washing, then measure it again immediately after the wash has been completed.

The water retention score is based on the percentage of the post-wash weight that is water: because washers should ideally remove as much water from the load as possible, the higher the water retention, the lower the score. The overall score is averaged across the four standard cycles.

Cycle Time

Today’s consumers want laundry products that are both quick and effective. When we run the aforementioned performance tests, we record the start and end time of each cycle, and calculate the time duration (in minutes) for each cycle.

The cycle time score is calculated using the time durations for the Normal and Quick cycles, as they represent the most commonly used cycle and the cycle that should have the shortest time duration, respectively.

Per Wash & Yearly Running Costs

Our figures for the cost per wash and the running cost of a washing machine are based on the combination of the following individual costs:

  • Electricity to run the washer
  • The cost of water
  • The cost of the gas used to heat the hot water

We do not include the cost of the detergent, as the cost and quantity of detergent used can vary widely.

We calculate these using the following assumptions:

  • An electricity cost of $0.13 per kilowatt hour
  • A water cost of $6.55 per 1000 gallons
  • A gas cost of $10.00 per 1000 cubic feet of water.

The yearly cost is based on an average of 392 wash loads per year, with 50% of these loads done in the Normal cycle, 20% in the Heavy cycle and 15% each in the Delicates and Quick cycles.

We believe that this approach provides a good representation of the typical use that a washer and dryer will get with an average family. However, the cost to run a washer can differ from user to user based on a large number of factors (electricity cost, water cost, gas cost, etc.), so this number should be used as an estimate for comparative purposes, not as a guide to the actual cost.

EnergyGuide – Our approach differs from the one used for the EnergyGuide labels seen on washers. These labels include figures for energy use and running cost, but are based on a different set of tests. So, our numbers will differ from the EnergyGuide numbers.

Washing Machine Subjective Assessment

In addition to thoroughly testing the capabilities of the washing machine, we also want to give our readers an idea of how it feels to actually operate the washer. Was the washing machine easy to use? Could you find what cycle options you wanted without the manual? Did the door have a soft close? Is the design purely functional, or does it have a nice finish? We answer these questions and more in an effort to give consumers as much information as possible about how this washing machine will look and feel in their home.

Dryer Objective Testing

Dryer Performance

We test the performance of dryers on four cycles: Normal, Quick, Delicates, and Bulky. For each test, we wet a standard laundry load (8 lbs. of sheets and towels for the Normal and Delicates cycles, 4 lbs. for of sheets and towels for the Quick cycle, and one large comforter for the Bulky cycle) so that the weight increases by 60 per cent to simulate the dampness of clothes that have just been extracted from the washing machine. We then place this in the dryer, along with two iButton sensors and set the dryer going.

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After the dryer stops, we remove the load and weigh it again to see how much water remains. We also retrieve the data from the iButton sensors to see what the temperature was inside the dryer while the cycle was running, and to ensure that the dryer did not “overdry” the load, or continue to dry the laundry load after everything was already dry.

Final dryer performance scores are based on two variables: how quickly the dryer removes the water from the test load and the peak temperature recorded during each cycle. Dryers need to remove water from the test load quickly, while maintaining a temperature low enough to avoid heat damage to the towels, bed sheets, pillowcases, and comforter inside the machine in order to achieve high performance scores.

Dryer Subjective Assessment

In addition to thoroughly testing the drying capabilities of the dryer, we also want to give our readers an idea of how it feels to actually operate the dryer. Were the dryer controls intuitive and easy to use? Was it easy to remove and clean the lint trap? Does the door close smoothly and securely? Is the dryer ventless, or is the venting flexible and easy to install? We answer these questions and more in order to to give consumers as much information as possible about the usability of a dryer.

If you want to read our most recent washing machine and dryer reviews, be sure to check out our library of laundry product reviews. To see some of the products we love the most, navigate over to our Best Right Now articles, where we talk about all types of washers and dryers, from the Best Washing Machines for Large Families, to the Best Top-Load Washers Under $1000, to the Best Dryers with Steam, and back again.