Dishwasher Power Usage - Changing Settings vs. Higher Star Rating
Dishwashers carry a star rating label to help you purchase the most efficient option within your budget.
One problem with star ratings is that for simplicity they only convey and compare one thing. For dishwashers, it is the energy usage of 7 uses per week at the ‘normal’ setting.
In other words: no mention of the different settings available and what impact they have.
Regardless of star rating, you can save a substantial amount of power, simply by changing the settings.
Power Usage of Different Settings - Eco, Normal, Auto, Intensive, Etc
The following are real-world test results from a several-years-old "3 Star" Beko dishwasher. I used a Power Mate Lite to conduct the power measurements. If you want to do some testing yourself our Reduction Revolution Power Meter will do the same job at a very affordable price.
|P2 30 Min||35˚C||0:30||0.72 kWh|
|P3 Eco - Half Load||45˚C||1:55||0.82 kWh|
|P3 Eco||45˚C||2:31||0.93 kWh|
|P8 Auto||40˚C - 65˚C||2:34||0.93 kWh|
|P4 Quick & Clean||60˚C||0:58||1.23 kWh|
|P5 Intensive||70˚C||2:23||1.37 kWh|
Dishwasher setting options.
These results clearly show that the settings you choose have a big impact on energy usage per load. For example, simply changing from 'Quick & Clean' to 'Eco' reduces energy consumption (and cost) by about 25%. In my experience, the Eco mode is just as effective as the others. You can save even more by switch to the 'half load' option which also works just fine. The short '30 Min' load showed even bigger savings, but it is only suitable for very light loads (and some hand drying is required).
Another important result is that the temperature level is more important than time taken. Generally speaking, the higher the temperature setting, the higher the energy usage. You can use this result as a rough guide to choose a more efficient option on your dishwasher.
Power Consumption by Star Rating
At the time of purchase, it's often hard to know how much of a difference one star rating is from another. With the above 'real world' usage table in mind, we can now review what the star ratings actually mean in terms of energy usage. The data shown below is for a '14 place setting' dishwasher.
|Star Rating||Energy Usage (per load)||Annual Cost*|
|1 Star||1.84 kWh||$192|
|2 Star||1.28 kWh||$135|
|3 Star||0.90 kWh||$94|
|4 Star||0.63 kWh||$66|
|5 Star||0.44 kWh||$46|
|6 Star||0.31 kWh||$32|
*Based on 365 loads per year and an electricity cost of $0.287/kWh. Source data is from the Energy Rating website.
From these results you can see that choosing a higher star rating can have an even bigger impact on energy usage than merely changing settings. However, this comes with a big caveat: the vast majority of dishwashers on the market tend to hover quite closely around the 3 to 4 star range.
In other words, a very high rated device may simply not be available at an affordable price. In which case, your best bet is still to play around with the settings you have available, and choose the lowest temperature option that works for you.
My dream dishwasher: an as yet unavailable / only theoretical 7 star dishwasher with next to no usage.
Other Ways To Save
As you may have gleaned, the key energy using part of a dishwasher relates to heating the water. So, if you already have an efficient hot water system (such as solar or heat pump powered by solar) you may wish to use a dishwasher model which allows a hot-water supply rather than the usual cold-water supply.
Don't forget that the best way to save energy would be to reduce the total number of loads you require. So if you can do a load say every 1.5 days, rather than daily, that will save even more energy again.
Want to know more? Buy our Plug-in Power Usage Meter to find out exactly how much your dishwasher costs to run.