Sense Sets the Record Straight About Running Your Dishwasher Every Day

In mid-February, Cascade debuted a new ad campaign featuring celebrity couples saying that they’re “doing it every night.” Of course, it’s not what you’re thinking. The ad is about washing your dishes every night. In its “Rethink the Sink” campaign, Cascade claims it’s busting myths about the efficiency of water use, energy and time of handwashing versus dishwashing. They say they’ve done the math to confidently recommend that running your dishwasher every night, with as few as eight dishes, will save water.

With many families stuck at home these days and dishwashers in use more than ever, people may be tempted to take Cascade’s advice at face value. And while some housebound families are already running full dishwashers on a daily basis, for those who aren’t, is this the time to start?

Since we’re obsessed with data about homes, we couldn’t resist crunching the numbers on this claim, and we discovered that it’s actually more wasteful to run your dishwasher every day. To analyze the real costs, we started with what Cascade says:

Contrary to popular belief, the dishwasher is designed to be more efficient than the way most of us hand wash dishes. According to Energy Star, certified dishwashers use less than four gallons per cycle. The sink uses four gallons of water every two minutes. But just how many dishes do you need to make the dishwasher a more water efficient choice? In a recent study, Cascade found that the average person spends 15 seconds hand washing a dish. In that time, the sink uses half a gallon of water. That’s why running your dishwasher with as few as eight dishes is all it takes to save water.

Using the dishwasher can also help you save costs on water and energy. According to Energy Star, if you are preparing at least two meals a day for a family of four, you could save more than 75% in energy and water costs by running your dishwasher instead of hand washing your dishes. Over the lifetime of the dishwasher, that’s $1,300 in savings.

Cascade is right that for a full load a dishwasher uses less water than hand washing, especially if you keep the water running rather than filling the sink to wash and rinse multiple dishes, but they’re wrong about the energy use. The energy required to heat hot water from a faucet is 0.1kWh to 0.15kWh per gallon, so you would need to use 10-15 gallons of hot water to equal the 1.5kWh of electricity used by an average dishwasher load. Assuming handwashing a single dish takes 15 seconds and a half-gallon of hot water, as Cascade’s research finds, you’d need to wash 20-30 dishes by hand with water running continuously to equal the electricity used by the average dishwasher.

A typical dishwasher holds 10-12 place settings (about 48-50 items), so we think that as long as you do full loads, the water versus energy tradeoff is reasonable, especially if you have an Energy STAR dishwasher. And, of course, using a dishwasher is a whole lot easier than hand washing!

But the more obvious issue with Cascade’s campaign is that they are trying to encourage you to run the dishwasher every night with as few as 8 dishes, versus waiting for a full load. This seems intuitively wrong, but how wrong is it? Here are the stats:

The average dishwasher uses 1.5kWh of energy and 6 gallons of water per load.

A new Energy STAR rated dishwasher is more efficient than average: it uses 1.2kWh and 3.2 gallons of water per load.

The EPA assumes that an average household runs their                  dishwasher 215 times per year.

Running every night instead would add 150 extra loads per year. If you use the energy data for the average dishwasher in most peoples’ homes and multiply 150 by 1.5kWh of energy and 6 gallons per load, you find that each household in the US would use an extra 225 kWh of electricity and 900 gallons of water annually if they ran their dishwasher daily.

How does this affect total water and energy consumption per household? Assuming 11,000 kWh per year and 49,000 gallons per year for total household use, this means a 2% increase in electricity use and 1.8% increase in water use for the household.  

While 2% might not seem huge in individual homes, when you consider that increase across the entire country (128 million households), it translates into $3.8B in electricity cost and over $2B in water costs. Given our increasing concerns about climate change and access to clean water, it is very irresponsible of Cascade to encourage people to run less-than-full dishwashers in order to sell more of their detergent.

It’s important that people pay attention to energy waste from dishwashers for another reason. A petition to “Make Dishwashers Great Again” advocates for “fast dishwashers” that complete their cycle in an hour. Since this would require more electricity and water, it would mean that efficiency standards would be relaxed. The Association of Home Appliance Manufacturers says that weakening these standards would actually incur additional costs to manufacturers and ultimately consumers. And by putting less efficient appliances into peoples’ houses, consumers will pay more on their utility bills.

Rather than heeding the advice of celebrity couples and dishwasher detergent brands, we recommend following the advice from ENERGY STAR: run full loads whenever possible and buy efficient dishwashers that will save you money with each load.

We’d like to know your opinion. Have you crunched the numbers on your dishwasher versus hand washing habits? Let us know at @Sense or