Washing the dishes is most people’s least favorite job when they come home from work.
The mess and scum of every dish, often accompanied by bits of half-eaten food, the gradual accumulation of grease in the original clean water, and the dripping of water and soap suds everywhere.
All in all, the result is good and necessary, but the process is awful.
That’s why, whenever families come into a bit of cash, they typically find themselves thinking about buying a dishwasher.
It is effective, both in cost and in cleaning, and even though it is large and clunky, the benefits outweigh the cost. Or do they?
See, even though washing the dishes is a pain, you know exactly how much water and soap you are using. This is not exactly the case with a dishwasher.
You can’t just tell or assume by experience how much it will use as the process is all internal. So, how much water does a dishwasher use, and is it too much?
How Much Water Does A Dishwasher Use In A Cycle?
The amount of water used by each cycle depends on several factors:
Volume Of Water Used Per Load
The more water used to wash one dish, the longer it takes for the machine to get through that set of dishes.
Number Of Cycles
Each cycle has its time period, during which it uses some water. If you run your dishwasher twice a day then this may translate to 2×10 minutes 20 minutes.
Amount Of Water Used Per Cycle
Not only does water volume affect how long it takes to wash a set of dishes, the way that the cycle works also affects the amount of water used.
For example, if you have a 3-minute cycle, you’ll be using 1/3rd of the water than if you had a 30-minute cycle.
So, what does all this mean? Well, firstly, let us consider the two extremes:
A) A 10-minute cycle would use 25% (10/40) of the water that a full 50-minute cycle would, so we can say that a 10-minute cycle uses 0.75 times the amount of water as a 50-minute cycle.
B) A 30-minute cycle would use 75% (30/40) of the total water that a 50-minute cycle would, making it the equivalent of 5 cycles using water at the same rate as a single cycle.
Now, since the average household has 4-5 sets of dishes per week, we can estimate that an 8-hour cycle would use approximately 7 gallons of water per week.
Is That Enough?
Probably! But wait! That number is based on the assumption that you wash your dishes once a week.
In reality, we’re likely to wash them multiple times a week, but how many loads of dishes can you realistically fit in a week?
If we were to take the average family size to be 4 people, who would normally eat each meal together, then we could estimate that a typical week would see between 1 and 4 people eating together each day.
If we presume that each person eats around three meals a day and that these occur roughly equally over the course of the week, then we can estimate that there would be between 12 and 84 individual plates being washed weekly.
In other words, if we want to take the maximum, we can estimate that we’d need to wash around 84 plates a week, or around 4368 plates a year (times the number of weeks in a year 52 by 84).
In fact, according to our calculations, washing each of these plates would require around 20 gallons of water per plate per year.
Now, this isn’t entirely accurate, because we didn’t account for things like the weight of the dishware, the temperature of the water, etc., but overall, I think that, provided you’re not washing dishes 24/7, it should be fine.
Since handwashing plates and bowls can take up to 85% more water than a dishwasher, dishwashers are a more environmentally friendly alternative.
But, What About Energy Use?
Well, energy usage is something else altogether.
As mentioned before, a dishwasher runs off electricity, so the energy consumption directly relates to the power draw required.
There are two main ways of measuring power consumption; Watts and Kilowatts.
Kilowatt-hours (kWh) measure the amount of energy consumed (in kilojoules) divided by the duration of the period of time that the appliance was running.
This means that one kWh equals 1000 J divided by the length of time that the appliance ran, e.g. if the appliance ran for an hour then it would consume 1000 J.
The wattage rating measures the instantaneous power drawn from the mains supply, i.e. the amount of energy used by the appliance per unit of time, e.g. 1 Watt 1 Joule per second.
The higher the wattage, the greater the instantaneous power draw. So, what’s the difference? Well, let’s say that you have a dishwasher with a 100 Watt motor.
This means that it will draw 100 Watts of power. And, assuming that the dishwasher is programmed to run for four minutes, then it will consume 200 kJ.
However, if it was programmed to run for ten minutes, then it will only consume 20 kJ.
To put this into context, consider that a 100 Watt light bulb consumes 10 W (10 Watts), which means that it uses 100 / 10 10 kJ every minute.
So, a 100 Watt dishwasher would only use about 2 x 10 kJ (20 kJ) per hour. That’s less than half a normal lightbulb.
Put another way, washing your dishes using a dishwasher would last approximately 18 times longer than washing them by hand!
Of course, this doesn’t apply to all dishwashers – some models may have lower power ratings than others.
For example, my old dishwasher had a 40 Watt motor, which meant that it took around 3 x 10 kJ to do the same job as the 100 Watt model.
The length of time a dishwasher can take means that they can end up drawing a lot of power from an electrical grid.
Therefore, it is best to consider whether it would be worth having a dishwasher in exchange for higher energy bills.
How much water a dishwasher uses depends entirely on the dishwasher itself, but for the most part, it would be about 0.875 gallons per hour of the cycle, which is a lot lower than washing the dishes by hand.
As such, if you can afford the expense it is recommended that you purchase yourself a dishwasher to save on water.
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