How we test dishwashers in the Reviewed test labs

We are appliance testing experts, putting all types of large appliances—including washers, dryers, refrigerators, and, of course, dishwashers—through our rigorous testing process to help you find the best one for you.

Dishwashers require one of the more elaborate setups we use in our testing labs in order to test every aspect of a machine. If you've ever wondered exactly how we get all those dishes so perfectly dirty so we can thoroughly test each dishwasher, this article is for you.

We've tested all the popular brands—Bosch, Samsung, Miele, Beko, Hisense, GE, KitchenAid, among them—across all types of countertop, portable, or built-in dishwashers.

We know exactly what differentiates a top-quality dishwasher from a dud.

Our team has been in the business of creating dishwasher reviews for over a decade, so we have a good sense of what makes a dishwasher worth the money. Here is an overview of how we test dishwashers and the rationale behind how we rate them.

To test cleaning, we need consistently dirty dishes

When it comes to evaluating which dishwashers are competent cleaners and which ones wash out of the competition, we're not afraid to get our hands dirty. The first step in our hands-on review process is making a mess—a series of very precise messes, to be exact.

The first step in our testing process is to prepare a slate of test plates with standardized food stains designed to emulate what you might run into in real life. "To test a dishwasher's cleaning ability, we created a variety of standardized stains in-house," says Jonathan Chan, our Senior Manager of Lab Operations.

This includes cooked egg, meat, pureed spinach, milk, baked-on cheese, and more. Each stain is applied evenly, measured, and photographed, so we can determine how much of the stain is remaining after any given wash cycle.

He further explained, "We draw our inspiration from both IEC and AHAM standards. However, our scoring model has areas of flexibility to test dishwashers with specific features or trends we're seeing in the real world. American households are getting more diverse, and Reviewed's testing labs are prepared to keep up."

We hand-measure stains so you don't have to!

Once we know exactly how much stain is on each and every dish, we're finally ready to let the dishwasher have a crack at cleaning them. We test each dishwasher’s three main cycles: quick, heavy, and normal by baking nasty food and beverage stains on 15 to 20 dishes that are then loaded into the dishwasher per the manufacturer's loading directions.

We also use specific stains when we test certain cycles because it more closely matches a common use case. For example, if you had a casserole dish with baked-on cheese or another stubborn stain, you'd likely rely on a heavy-duty cycle as opposed to a quick wash cycle.

According to David Ellerby, Reviewed's chief scientist, "No dishwasher is perfect, and at home, you probably don't expect your dishwasher to completely remove the toughest stains. In the lab, we're not that reasonable. We test dishwashers against food stains that are baked on in the oven. Challenging dishwashers with the worst possible conditions is the only way to find the very best."

Once dishes come out of a cycle, we hand-measure any stains remaining with a tape measure, to calculate exactly how much of the initial stain is still remaining after a wash.

How we separate a "good" performance from the rest of the pack

One thing that's important to keep in mind when evaluating dishwashers is where the goalposts are that delineate a "good" performance from one that's merely OK—or outright lacking.

On most cycles, the average dishwasher is able to clean over 90% of our test stains away, with excellent dishwashers cleaning over 99% of all stains. Worse performers fall into the 80–90% range. Unless a dishwasher has an issue, it's going to fall in that 90–99% cleaning range.

This creates three general ranges for performance: Excellent dishwashers clean 99% of stains or more, while average dishwashers clean away over 90% of all stains, and poor dishwashers fall below that threshold.

This may seem like a relatively small range to work with—and it is!—but this narrow field makes a lot more sense when you think about it practically. If we're staining the entirety of the interior of a bowl, and 90% of it is getting cleaned off, that still means 10% of the stain is remaining after a wash cycle.

For the overwhelming majority of users, if 10% of a plate is still gunked up after a wash cycle, it's still a dirty plate. Most users consider a plate still dirty if it has more than 1% of a stain remaining. Of course, because we're testing with more intense stains than the average user might force on their own dishwasher, we're also more lenient with our scoring.

Stains not getting washed away properly can show gaps in spray arm coverage or an error with the wash system. Stains that get washed off one plate and onto another are called redeposit and indicate an issue with the filter.

We also take note of any abnormalities we see, such as plates in one location getting a better or worse clean than those placed in other locations.

Are the dishes dry?

Whether or not a dishwasher fully dries your dishes is a big point of dishwasher contention for a lot of users. Once dishes come out of a wash cycle, we let them sit for 30 minutes to allow them a reasonable amount of time for any drying technologies to work their magic. If the instructions recommend we open the door to facilitate this process, we do so.

We want to see exactly how dry the dishes are getting after a wash cycle, from flatware to plastic containers. Plasticware is actually our most important component to this test, as most modern dishwashers are pretty good at getting traditional dishes dry: Ceramics and glass tend to hold heat well, so the heat remaining after a cycle is often enough to get any standing water to evaporate. Plasticware doesn't hold heat as well, which is why those Tupperware containers always seem to have a small lake on top of them after a wash cycle.

This test is particularly important because one of the most common complaints about dishwashers is that they don't completely dry dishes after a wash cycle. The reason for this perception is partially due to newer Energy Star standards for dishwashers: Older models used to have integrated heating coils, which were extremely energy-expensive, but did get dishes dry.

This is one area where built-in models often have an advantage over countertop or portable dishwashers: They have more space to circulate drying air around the dishes.

User experience: How easy is it to actually use the dishwasher?

We don't just rate products based on their objective test performance: We also make sure to use each dishwasher normally, just like any owner would. This helps us get a feel for the overall user experience.

Do all the racks slide smoothly? Can you adjust the height of the top/middle rack? Is there a third rack? Can you fold down the tines? Are there bottle jets? Does it have front-facing or top controls? How do they feel to use?

If working with a smart dishwasher, how easy is it to start up a cycle using the app controls? If it's a portable or countertop dishwasher, how easy it is to pick up and reposition around your kitchen? We consider all of these factors and more.

This holistic approach also helps us contextualize a dishwasher's price. If a model is advertised as high-end or luxe, chances are the justification for its price will be accounted for in less tangible features than raw stain-scrubbing power. If you're buying a higher-end machine, you expect it to look and feel the part, otherwise you won't feel like you've made a good investment in an expensive appliance.

Our testing is always evolving

As dishwasher technology evolves, so does our testing. One of the newer features that has come into its own on dishwashers is the third rack. When we first started testing dishwashers, none of them had a third rack; at this point, most midrange dishwashers and above have them. As such, we're currently developing more rigorous testing around how well items placed on the third rack get cleaned. This will allow us to directly compare the performances of dishwashers that have this useful feature.

Just as with all the other categories we review, as newer features get rolled out, we'll update our testing procedures to accommodate them!

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Prices were accurate at the time this article was published but may change over time.