Washing Dishes by Hand or Dishwasher: Which is more Eco-Friendly? [Infographic]
I have a confession to make.
I try to live a green life, reduce my carbon footprint and be environmentally conscious. My shampoos are biodegradable, my sunscreen eco-friendly and I buy local produce. I also wash dishes by hand under running water.
Continuous running water.
My confession is answered by retorts of hypocrisy and my environmental stance is questioned but I simply can’t stand washing dishes in a basin filled with stagnating, food-filled sink water.
Therefore, I took it upon myself to calculate the amount of water, dish-washing detergent and energy used up with three dish-washing techniques:
- Washing dishes by hand under running water
- Washing dishes by hand in a filled sink
- Using a dishwasher.
Savings or costs of each method were calculated with the following data:
- Price / litre water (in Britain) = ~0.002$/L.
- Price / kWh (United States average) = 0.12$/kWh.
- Price / therm for gas (United States average) = 0.93$/therm
- Average water use / cycle of a dishwasher (Energy Star) = 9.4L.
- Average dishwasher loads per year (per family of 4) = 110.
- Energy consumption / year of a dishwasher (Energy Star) = 200kWh.
In hope of redemption, I tried to answer the question, which of these methods is the greenest? That answer, surprised me.
Washing dishes by hand under running water
There are two variables to confine: (1) the flow rate, and (2) the average time spent washing.
After a few tests, I found that I run water at a rate between 550 ml and 850 ml/10 seconds. Taking the middle ground as average flow rate, I then measured the time it takes to wash a dinner plate. After tests on messy and clean plates, it took on average 20 seconds to clean the dish.
Our dish washing rate is then 1.1L to 1.7 L per plate, which costs 0.0022 to 0.0034$.
Assuming a family living together, washing for an average of 15 minutes a day and at eating at home 6/7 days (vacations, weekends, nights out etc.) this method accounts for 15 500 to 24 000 litres of water used a year at a cost between 30.97 to 47.86$. Averaging it out, dish washing by hand under running water costs 39.42$ and uses 19750 litres per year.
That’s a shocking amount of water.
(The cost of detergent is an additional 10$/year and hopefully that detergent is biodegradable. If you would like to learn more about biodegradable detergents, we wrote an article on biodegradable shampoos that details the effects and processes of eco-friendly biosurfactants.)
Washing Dishes by Hand in a Filled Sink
The only variable in this scenario is the size and volume of the sink required to adequately cover most dishes, pots and pans.
The sink has to be filled deep enough to cover some of the dishes, but doesn’t need to be filled to the top. For this example, my sink volume is 13530 cm3 (41 x 33 x 10 cm) or 13.53 L. Assuming you wash the dishes twice a day (morning and evening), each day your consumption will be around 27 L. Applied over the year, that’s some 9855 L of water at a cost of 19.71$.
That’s a savings of 10000 litres of water and around 20$ per year by changing your dish washing habits.
However, we don’t wash dishes under cold water, so let’s now factor in the water heating costs in both examples.
Gas or electric heaters matter
The office of energy efficiency & renewable energy has a handy calculator to estimate the cost of running electric or gas water heaters.
For the calculations, we assume a 50/50 split between cold and hot water. Therefore, the yearly cost calculated by the website is halved.
With an electric water heater:
- Using the first scenario of 19750; yearly energy costs are 67.25$.
- In the second scenario of 9855 litres; yearly energy costs are 31$.
With a gas water heater:
- Using the first scenario of 19750 litres; yearly energy costs are 24.75$.
- In the second scenario of 9855 litres; yearly energy costs are 12.5$.
The cost of washing your dishes by hand under running water run with an electric and gas water heater run respectively from 111.67 to 69.17$ per year.
The cost of washing your dishes by hand in a basin with an electric and gas water heater run respectively from 55.71 to 37.22$ per year.
It’s looking like we have a clear winner …
Dishwashers are mad efficient
A dishwasher requires energy, water and detergent to effectively operate.
Energy consumption from modern dishwashers is lower than what it took to illuminate old computer CRT monitors. This drives the yearly operating cost down to only 24$.
Modern dishwashers also use an incredible low amount of water per wash. By Energy Star estimates, only around 1000 litres of water are consumed per year, at a cost of 2$ and an annual heating cost between 9 and 4$.
Due to this efficiency, a modern dishwasher should cost approximately 32.50$/year.
Detergent prices vary, but users report cost per loads of around 0.08$ adding 8.8$ to the yearly usage costs.
In total, a dishwasher runs on around 41.50$ of detergent, water and electricity per year.
Dishwasher or dish-washing: The winner is …
The most cost effective way to wash dishes is: washing your dishes by hand in a small water-filled basin.
Although, a dishwashers year operating costs may be lower, we have not factored in the water or the specialized detergents that are required to clean the machine. Servicing costs are also not included, and obviously the cost of the dishwasher itself will never been recouped if you use the alternative basin method.
Now let’s address the elephant in the room i.e. how do we define which method is the “greenest”?
We could use the amount of water used, which would clearly favor the washing machine. Or, maybe the CO2 emissions, which would reflect the electricity costs and also favor the dishwashing machine. Despite those two factors, dishwashing machines are not greener than hand washing.
Consider the raw materials, energy, water and shipping in the life cycle of a single dishwasher. Consider the motors and oil, the PVC or PP plastics, steel and ultimately the infrastructure built to recycle the old dish washing machines. With hand washing as an alternative, a dishwasher cannot be called green.
Washing dishes by hand is hands-down, the greenest and most spartan way of cleaning your dishes.
What do you think? Have we missed some factors in our calculations, or over-estimated something? Write to us below in the comments.
P.S. We have not factored in the time saving aspects and convenience of a dishwasher over hand washing. That was not the point of this article, but they are undeniably strong arguments for a dishwasher.
Want to share this infographic on your site?
Simply copy and paste the code below into your blog post or website: