Dishwashers, Energy Star, water efficiency and the environment. A consumer guide.


Flickr photo courtesy of fixedgear.

Do you hand wash your dishes because you don’t want to “waste” water and energy by using the dishwasher? If so, then consider this:

If you run hot water through your sink and keep it running, you are using at least 2 gallons of water for EVERY MINUTE that you have the sink turned on. And that is assuming that you have an efficient kitchen faucet. Does it take you 10 minutes to do the dishes by hand? Well, then you just used at least 20 gallons of water!

No way, you say! I don’t keep the water running. I fill up the sink and wash my dishes that way. Well, how long does it take you to fill up the sink? More than 3 minutes? I just did a test with my own kitchen sink. It takes my faucet 30 seconds to fill up a 1 gallon container, so my faucet is putting about 2 gallons per minute. After 4 full minutes, my kitchen sink was just over half full. That’s 8 gallons of water.

Not too bad, right? Wrong!

Want to know how much water a new Energy Star dishwasher uses each time that you run it? Just 4 gallons! Okay, so what about a regular new dishwasher? How about a mere 6 gallons. It’s right there on the Energy Star site for you to see for yourself.

Want to know how much it will cost you to use your dishwasher for a whole year under average conditions? Try under $30!

Don’t believe me? Look at the government mandated EnergyGuide label at your local appliance store and see for yourself. Outside the USA? The Australian government requires both Energy Ratings and WELS water ratings to be provided on every unit. EU Energy labels also show the specific amounts of energy and water used, with a grade scale from most efficient to least efficient.

Even if you think the EnergyGuide label is overly optimistic, then double their numbers and you’re still around $60 a year.

Compare this to taking a shower, where you’ll use 2.5 gallons per minute if you have an efficient showerhead. Just one person taking a 5 minute shower will use 12.5 gallons of hot water. And you were worried about the impact of your dishes!

From a strictly practical perspective, I could stop right now and sum up this post with one sentence that says, “Use your dishwasher to save water and energy.”

Want some extra eco-credit? Here’s what you do:

1. Only run full loads. You’ll be using even less energy and water than if you run twice as many half filled dishwasher loads.

2. Air dry your dishes instead of using the heating element. If you run your dishwasher at bedtime, you won’t unload it until the next day anyway, so there’s plenty of time for the dishes to drip dry. That makes your dishwasher even more energy efficient than it already is!

3. Take it easy on the pre-rinsing. I’m not going to lie and tell you that modern dishwashers don’t require any pre-rinsing at all because they work perfectly and your dishes will sparkle happily ever after. I own a brand new Energy Star Kitchenaid dishwasher that had high reviews from Consumer Reports, and I still have to pre-rinse. But I only have to scrape most plates and only use a brush under the faucet to get those stuck-on cheesy areas, and the dishes come out clean. Test out how little pre-rinsing you can get away with using your own dishwasher! You aren’t being lazy, you are saving the environment.

4. Use a phosphate free dishwashing detergent. Phosphates are a good thing to avoid because they encourage algae growth when they get into our waterways. The good news is that Consumer Reports rates several phosphate free dishwashing detergents highly. “The Ecover tablet and powder, Citra-Dish, 365 Everyday Value, and Seventh Generation do a good to excellent job cleaning.”

Anyone else have any good dishwasher tips or anecdotes they’d like to share? Leave a comment!

PS When I was looking for photos for this post, I noticed a disturbing number of photos of cats playing in dishwashers on Flickr. What’s up with that?

PPS It isn’t just cats, either! There are plenty of dogs, and even a goat.

20 thoughts on “Dishwashers, Energy Star, water efficiency and the environment. A consumer guide.”

  1. Which Energy Star dishwashers use 4 gallons? I checked the user manual for several Energy Star dishwashers and found that most use 6.5 gallons for a normal wash. A new GE Profile uses 7.5 gallons for a normal wash (yes, it’s Energy Star). You have to check the manual for each model to know the real story.

  2. Thanks for the comment.

    I was going by what the Energy Star site itself says, which I thought to be the most reliable source.

    I’m going to look it up with my own new Kitchenaid dishwasher as soon as I get home though, to see what my owner’s manual says about how much my dishwasher uses. I’ll let you know!

  3. I checked my Kitchenaid manual, and here are the results.

    The normal cycle uses 3.9-7.1 gallons.
    Heavy duty cycle – 6.9-7.8
    Rinse only uses 1.8 gallons

    Ellen, did the manuals you looked at have a range like that, or did they give a single number?

    I know a lot of dishwashers now have sensors that wash longer if your dishes are super dirty.

    I would say that I’d still come out ahead using the dishwasher, which uses an extra 4 gallons on the heavy duty mode in the worst case scenario. That’s only 2 minutes of running the kitchen faucet.

  4. “Want to know how much water a new Energy Star dishwasher uses each time that you run it? Just 4 gallons! Okay, so what about a regular new dishwasher? How about a mere 6 gallons.”

  5. Commercial dishwashers often use the greywater from the last rinse cycle for the first cycle on the next load. I wonder if any home machines do this.

  6. I was wondering if it is still necessary on newer model dishwashers to rinse dishes before loading them into the dishwasher, and do the dishes come out clean? I don’t have a dishwasher partly because of my negative experiences with them, basically having to wash the dishes before and after anyway. Not as energy efficient in such cases.

  7. Hi Amy,

    Here’s the deal. You SCRAPE the dishes off before you put them in the dishwasher instead of rinsing.

    The only time that you still might need to rinse is when you have cheese stuck to the plate. If you have a scrub brush, you hardly need to use any water at all.

    I barely scrape my plates at all in my Energy Star dishwasher, and they come out spotless. It’s only when there is cheese stuck to the plate that I have to pay attention at all before I put something in.

    My wife gets grossed out by putting the plates in the dishwasher when they still have stuff on them, and so she likes to rinse them off first. That totally defeats the purpose of having a dishwasher! You want the DISHWASHER to do the work instead of YOU!

  8. I used to be anti-dishwasher, then I realized how much water I was using that I could be saving. Now, we almost exclusively use it. Both my girlfriend and I are super water conscious and try to save as much as we can.

    We started using the Ecover tablets, and they work great.

  9. Just want to say thank you for this post! I have been trying to convince my husband for three weeks that we need to use the dishwasher to cut costs and he just doesn’t believe me. This from the man that thought we would save money going to the laundry mat lol. I am armed with info in the fight to keep the water bills down and to get out of washing dishes.

    Oh, by the way..the water company told me that a dishwasher uses more water than washing in the sink! What morons.

  10. Has anyone taken into account the amount of electricity (pretty expensive in this day and age) that dishwashers use, and not just the amount of water? Washing dishes by hand uses NO electricity. So what’s the difference?

  11. According to, “According to researchers, a load of dishes cleaned in a dishwasher requires 37 percent less water than washing dishes by hand. However, if you fill the wash and rinse basins instead of letting the water run, you’ll use half as much water as a dishwasher would.” I wonder if anyone has exactly measured this?

  12. We wash up once or twice a day. We use a plastic washing up bowl that holds 2 gallons full. We half fill it – that is about 1 gallon. We do not rinse. That is less hot water than any dishwasher.

    I’ve done that all my life. It is how I was brought up. I’m English.

  13. I’d like to add that the idea that dishwashers use less power and water to clean dishes than washing up by hand is one of the most successful pieces of greenwash there has been so far, and as for Lars – he should take a housekeeping course. Leaving the tap running indeed! What total nonsense.

  14. NO home dishwasher uses gray water. That would be dangerous. You could literally kill a person with such a foolish action.

    I have never seen a nfs rated washer do such a dangerous thing. Pretty sure it is against plumbing codes of any modern country.

  15. Ok people for me it isn’t the amount of water i use. The amount of electricity and the products that you buy is the money. The dish detergent and the dryer stuff for the dishwasher costs u money as the soap that u buy for the hand washing isn’t that bad. So u go ahead and use your dishwasher.

  16. On top of that if u rinse dishes before u put them in the dishwasher then u are doing just about the same things as doing them by hand.

  17. Becky: If you wash with hot water, you do use energy to hand wash; the water heater uses electricity and/or gas. I am very energy conscience but am also a germaphobe so there is no way I could do what Jane Leaper (above comment) does. I had a Miele dishwasher and while the amount of water and electricity was lower than most domestic models at the time, it didn’t get the dishes very clean and I would have to rinse the littlest bits off my dishes. I opted for a Kitchenaid for my new house which, with the most recent models, is comparable in energy efficiency to the European models.
    You can put a gallon or less of water in your sink or a bucket and leave dishes in it throughout the day and then use a brush to wipe off the dishes as you put them in the washer. I keep a bucket in my sink to catch the (gray) water and use it for watering plants, cleaning out garbage cans, compost bins, etc.
    The key to either hand washing or using a dishwasher is being diligent with your process; never letting the faucet run, compost instead of using the garbage disposal and doing a large load at one time instead of smaller ones (sometimes I only do a load every 2 or 3 days). Whether you choose to hand wash or use a dishwasher, the most important thing is that you are being conscientious.

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