Running the dishwasher on hot water can save energy – but it depends on how the hot water is heated and how far it travels to the dishwasher.
Heating water costs energy and money
Tap water is around 10 to 15 degrees cold. For washing and drying, dishwashers usually heat the incoming water to about 50 to 55 degrees Celsius. This consumes a lot of electricity. It seems to make sense to connect the inlet of the dishwasher directly to the hot water supply. The dishwasher can save energy if the water is already warm when it reaches the appliance.
Hot-water connection usually not a problem from a technical point of view
Technically, a hot-water connection is not a problem for most dishwashers – usually you will find a hint in the instruction manual. But a hot water connection does not always save electricity.
Hot water connection can shorten program duration
The first energy saving comes from the duration of the program. Since the heating up of the water is mostly omitted with a dishwasher with warm water connection, the cleaning programs are usually a few minutes shorter.
Long line means more reheating
However, the longer the pipe from the water heater to the dishwasher, the less energy-efficient the hot water connection. Reason: The water in the connection pipe is usually not really warm, but cooled down. Initially, a relatively large amount of cool water flows into the machine – despite the hot water connection. The dishwasher has to heat it up with electricity, the energy saving disappears.
Independent. Objective. Incorruptible.
Heating twice wastes energy
It makes no sense to have a dishwasher with a hot water connection if the tap water is heated electrically anyway. Then the device must heat the water electrically a second time. If the line is also long, electricity consumption can even increase instead of decreasing – consumers pay the price.
Only solar is wonderful
If the hot water is heated in an environmentally friendly way by a solar system, a hot water connection for dishwashers is almost always worthwhile. Even if solar energy is not sufficient in winter, the sun alone provides hot water for more than half the year.
The dishes will be clean either way
By the way, it doesn’t matter whether hot or cold water flows into the dishwasher. How well the dishes are washed and dried does not depend on the temperature of the incoming water. Program sequence and temperatures for cleaning and drying hardly differ from each other.
Save energy with the Eco program
Energy can also be saved by using the "Eco" program, which rinses at lower temperatures but takes several hours to do so. In modern dishwashers, "Eco" must be preset as a standard program or offered first in the program menu.
For more information, see our dishwasher test.
This message is on 26. August 2010 on test.en appeared. It was installed on 11. March 2021 updated.
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We’ve had solar thermal on the roof for a few years now and have been saving approx. 25-30% of our previous gas consumption. Since then, our dishwasher has also been hooked up to hot water and saves electricity. Today I accidentally measured the initial temperature of the dishwasher. Yesterday we had to mourn the death of our dishwasher heater and thought, we could rinse perhaps with the hot water from the line. From the faucet at the sink it ran with almost 60°. When the dishwasher had filled and wanted to start cleaning, it was still 40 °, because the warm water meets a cold machine and on usually not preheated dishes and cools down first of all quite nice. This is too little if the machine can not reheat.
Laundry MUST be heated slowly because of many types of stains and cooled slowly to avoid permanent plissee, therefore a WW connection would be nonsense not only in terms of environmental protection, but also in terms of textile protection.
"At the beginning – despite the warm water connection – a relatively large amount of cool water flows into the machine." – Doesn’t this make sense anyway for the first rinse cycle?
It depends, of course, on whether there is a circulation pump and how long the lines are between the water heater/storage tank and the dishwasher.
Which manufacturer has dishwashers with separate hot and cold water connections in its program??
Another note on the subject of hot water connection of the dishwasher:
To dissolve proteinaceous dirt it is better to start with cold water. If hot water is used right away, the protein contamination could become even more entrenched.
Possibly the cleaning performance is thereby somewhat lower. Certainly, this disadvantage is compensated today by more modern rinsing agents. In the past, there was a warning in the operating instructions of the machines that the cleaning results could be worse if they were connected to hot water.
So my WaMa always makes a few rinses after washing to get the soap out of the laundry again. I guess, that consumes more water than the actual washing cycle.
With WW connection I have to make them with warm water. This is absurd!
Ditto the pre-rinse at the SpuMa. This takes place unheated. There you want to chase WW in?
The times with the hot water connection of the dishwasher are over.
The WW connection of washing machines and dishwashers is also associated with some disadvantages.
A PV on the roof and if it is only a balcony system generates electricity.
Electricity is good to use for all appliances in the house and around the house, the dishwasher then just runs at times of sunshine, without sun the sense of a hot water connection is also very limited.
And when the reference to water heaters comes here, battery systems are becoming increasingly viable, battery prices are already affordable.
Thermal solar system are a discontinued model.