Eli5 how does the eco setting on a washing machine save energy and water by washing the laundry for *longer*?

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Edit: Thank you to everyone that replied!

In: Technology

9 Answers

Anonymous 0 Comments

Whenever you clean something, there are 5 basic elements involved: Water, Agitation, Time, Chemical, Heat (WATCH for short!). Think of them arranged as the wedges of a pie chart. For something to get properly clean, there is a balance of these 5 things. You can reduce one or more of these elements, but in compensation, one or more have to be increased.

In modern washers, the amount of water, chemical, and heat is reduced, at the expense of time and agitation. The washer is relying more on the mechanical action of agitation to shoulder the load of soil removal, but obviously, this takes longer. In terms of our pie chart, W, C, and H wedges are smaller, and the A and T wedges are made larger to compensate.

As someone mentioned, it takes less energy to agitate the clothes in the wash wheel than it does to heat the water to higher temps, hence the energy savings.

Anonymous 0 Comments

It’s model dependent, but the most eco friendly thing a washer can do is an extended spin cycle to dry the clothes. Every drop it can wring out of the cloth before the washing is done is a huge energy savings for the dryer.

Anonymous 0 Comments

If I have to wash my clothes 2-3x to clean them as well as a non-HE machine, how is that “high efficiency” or “Eco Friendly”?

A 20 liter HE washer uses approx 45 liters of water per load, and die to the low water level, it requires 2-3x the number of cycles to clean clothes properly… So roughly 135 liters of water total.

A non-HE washer is 30 liters and uses approx 60 liters of water per load. It requires that once, and the clothes are clean. 60 liters total.

HE washer uses 50% of the electricity that a non-HE unit does, power load. Requiring 3 cycles to clean clothes results in 150% electricity usage in comparison to a non-HE unit only requiring 1 cycle.

So, it takes way longer, uses more water, washes less per load (thus requiring more loads/cycles overall), and uses more electricity.

Sounds like a bullshit scam to me.

Edit: liters, not gallons

Anonymous 0 Comments

The energy required to heat the water is significantly greater than the energy to pump the water or spin the tub.

A typical electric water tank is 4500 W. A washing machine’s boost heater (for better machines, if incoming water is too cold) would be 1500 W. A pump might be 100 W. The main drum motor might be 300-500 W.

Kinetic energy to heat 20 L of water from 20 to 40 C: 1,600,000 J

Kinetic energy to spin a stopped drum full of 40 kg clothes+water up to 300 rpm: .5 × (.5 × mass × radius^2) × (angular velocity)^2 = 1.2 × (37 rad/s)^2 = 1600 J (assuming solid cylinder for moment of inertia)

Anonymous 0 Comments

The eco setting on my washer uses colder water than the warm setting. Heating water takes a lot of energy. A big chunk of household energy use is just heating water and heating|cooling air.

Anonymous 0 Comments

It saves water by simply washing the clothes for a longer time. I’m not sure if that actually saves any power in the end.

Anonymous 0 Comments

It uses the water, longer.
therefore it can get away with using less water, since it uses that same water more efficiently.

think of how long it takes for water to seep into a thick cloth

Anonymous 0 Comments

The motor of the washing machine uses very little power when it’s just moving the clothes around. It’s a bit more during the spin cycle, but that doesn’t last very long.

The vast majority of the power is used to heat the water, so if you can use a lower temperature and/or less water and instead just have the motor do its thing for a longer time, you use less energy (and water) overall.

Anonymous 0 Comments

Washing machines use heat to speed up the chemical reactions between the clothes and detergent. And heat takes a lot of energy to generate. You can use less energy by letting them react colder but slower.