Dishwaters can consume a considerable amount of energy if run thoughtlessly.
A dishwasher on a full load consumes about 15 litres of water on average, capable of cleaning up to 144 items. The average consumption by a dishwasher varies from one brand to another. However, the exact water utilisation is always printed on the energy rating label present on all the dishwashers. Some energy-saving models can bring down this amount by 30% and pre-rinsing can reduce overall water consumption. Miele’s dishwashers are considered top-rated in Australia, capable of using 6.5 litres of water. Some of the models manufactured by Bosch are known to consume as low as 6 litres for cleaning dishes equal to 13 meals. A standard dishwasher can consume 9.5 litres of water. A modern dishwasher can run on a half load and clean anything present in the bottom zone only.
A dishwasher's power rating identifies its energy consumption. Ideally, a 3-star dishwasher running for 30 minutes at 35 degrees Celsius will consume around 0.72 kWh of electricity. According to some sources the retail price of electricity in South Australia is 43.67c per kWh, which is the highest in Australia. Therefore, one load of a dishwasher running for 30 minutes will consume approximately 32c in South Australia. The energy-rating of dishwasher range from 1-star to 6-star. A 6-star machine will consume about 0.31 kWh per load. It's important to know that this power consumption will change with a change in settings. For instance, though a 3-star machine uses 0.72 kWh, this amount can further rise to 0.90 kWh with tweaked settings.
On average, a standard dishwasher consumes around 9.5 litres of water for washing dishes, which would require 60 litres of water if washing them by hands. Washing dishes for one person by hand would need around 11 litres of water every day. Assuming that an average household in Australia has three members, the total water consumption would reach 33- 35 litres per day. Dishwashers are capable of bringing this amount down to 15 litres. People end up using approximately 3.5 times more water than a dishwasher to clean the exact same load of dishes.
The cost of one load in a dishwasher includes electricity costs, water charges, etc. An assumed electricity cost is $0.12- $0.40 per load if a dishwasher is run on cold wash under normal settings. Each load consumes about 13-15 litres of water. Assuming the standard rate of water in Perth to be $2.2/KL, the cost of water per load will be $0.28- $0.33. You can expect to spend around $0.33 + $0.40 = $0.73 per load. Add the detergent cost to this amount to find the estimated cost per load in a dishwasher.
Rating | Estimated kWh used |
|---|---|
1 star | 1.8 kWh |
2 star | 1.2 kWh |
3 star | 0.9 kWh |
4 star | 0.6 kWh |
5 star | 0.4 kWh |
6 star | 0.3 kWh |
Dishwaters do consume a considerable amount of energy if run recklessly. However, with the most optimised settings, they become energy efficient and people can save some energy. Energy usage of a 3-star dishwasher per load at various settings is listed below.
Dishwasher setting | Estimated energy use |
|---|---|
30min setting | 0.7 kWh |
Eco (Half load) | 0.8 kWh |
Eco | 0.9 kWh |
Auto | 0.9 kWh |
Quick & Clean | 1.2 kWh |
Intensive | 1.3 kWh |
Different settings mentioned above operate at different water temperatures. The heater and pump are the highest electricity-consuming components, which means that running a dishwasher on cold water will allow users to save a significant amount of electricity.
Dishwashers are capable of utilising hot water and have a separate water inlet connected to the hot water pipeline. This allows a direct flow of hot water into the dishwashers, which eliminates the need to heat the cold water inside the machine. Most dishwashers are shipped with a heating element at the bottom - a circular ring-style shape. This element is meant to heat the cold or regular water right inside the machine at an average rate of 1 degree Celsius per minute.
The least water consumption per load is 6.5 litres in some machines but you can expect to use up to 15 litres per load. Most people exclude the amount of water for pre-cleaning the dishes. This process is done by hands that consume up to 3- 5 litres of water. Therefore, add 3 to 5 litres to 15 litres, making a total of 18 to 20 litres of water per load in a dishwasher.
Modern machines now use at most 15 litres of water per load. Cleaning the exact same load by hands can consume nearly 3 times more water. Dishwashers can wash and rinse 14 place settings.