Laundry Science 101: Hot Water Vs Cold Water
There are good reasons to use cold water and good reasons to wash on hot so let’s explore why temperature is important in certain situations and clear some myths and misconceptions about washing on cold and hot water.
The cost/energy savings of washing in cold is obvious. I won’t argue with that for a second. From an economic standpoint, cold water wins hands down. From a cleaning standpoint – you may have to weigh getting clothes cleaner vs how much money you are spending per load.
In a previous post, I discussed the basic principles of washing. Lets review.
The process of washing laundry is broken into a ratio of
Here’s the monkey wrench – Cold water changes a few things. Cold water requires that you not only run your machine longer and/or use more chemicals (soap),but also on the drying side of things, your clothes may have to dry for longer in the dryer.
This is because cold water weighs more so natural fabrics like cotton actually soak up more water, which will add to your drying time.
Hot water is most often 10 degrees colder when it arrives at your machine from when it leaves your hot water heater. In washing terms, hot water is 130 degrees Fahrenheit (54.4 Celsius) or above. Warm water is generally between 110 and 90 degrees Fahrenheit ( 43.3-32.2 Celsius). Cold water is between 80 and 60 degrees Fahrenheit (26.7-15 Celsius).
When you are washing at 80-60 degrees Fahrenheit, soap works 70-90% less effectively within the same amount of time time as it would in warm water. If your cold water is below 60 degrees Fahrenheit (15 Celsius), clothes are unlikely to be cleaned very well.
You may want to try using a candy thermometer when you are running the machine to see what the temperature actually is when washing. If you are running cold loads and the temperature is below 60, tell your machine to wash on warm. Additionally, your cold temperature can change seasonally, so if you are in the frozen north, consider dialing up to at least warm to wash your clothes in the winter.
Cold Water = a need for increased wash time (or increased chemicals) and possible longer drying time.
Hot water = decreased wash time (or decreased chemicals) and possible shorter drying time
In some cases your washing machine will automatically give you a longer wash time if you select a cold cycle, but when the settings are completely up to you – if you didn’t know to increase the time when decreasing the temperature, you might be wondering why your clothes aren’t getting properly clean.
All things considered, you are most likely still saving money using cold water, even if you have to run the machines a little longer. In that regard, cold water wins. In addition, you can counteract the longer drying time by using Wool Dryer balls. Three to Four dryer balls in your dryer will cut down on drying time. Wool Dryer balls are a one time investment that save a lot of energy and time.
To find out how much you’re actually spending per load, check out this useful resource that will allow you to enter in your machine type, settings, and everything else.
Cleaning and Sanitizing Power vs Energy Efficiency
It is when you get to heavily soiled items that you may want to reconsider if it’s worth it to save a few cents or a few watts. Hot water is wasteful. You have heat up to 40 gallons of water if your machine is not High Efficiency. But it’s not wasteful if you need to get things really clean and kill germs. If someone in your household is sick or has a compromised immune system, it’s best to wash on warmer settings. Things like cloth diapers really need to be washed on warm/hot (explained in more detail below).
Hot water is better for disinfecting, although this can also be a bit of a myth.
Unless you are using boiling water, you are not killing off everything. Even adding a few drops of tea tree oil won’t kill everything. The heat of the dryer doesn’t necessarily kill everything either, so don’t rely on your hot dryer to disinfect. For killing everything you need to use the UV rays of the sun. The sun is free – and will kill bacteria as your garments hang on the clothesline. Bleach is another disinfectant option, though it does degrade fabrics (UV light does too, but not nearly as much as bleach). Grapefruit Seed Extract and Tea Tree oil are other disinfectant additives. I’ll do another post on disinfecting and cover all those bases, but they were worth the mention. The other benefit of a clothesline is that it’s 100% free. If your clothes come out a little stiff after hanging you can run them in the dryer for 10 minutes and you’re still using far less electricity to dry. Another money-saver in the drying department are Dryer Balls. Those are awesome and help cut down on drying time and are a great investment. If you wash with Eco Nuts you don’t need a fabric softener, but if you’re using a different detergent, these do help soften fabrics pretty well.
Back to the subject of cleaning power, almost all body fluids are better removed from fabrics at warmer temperature. The reason is that your body is warm and those fluids are soluble at that temperature.
If you need to remove fluids like urine, blood and sweat – then a WARM (not hot) rinse is the answer. Certain fabrics can set stains (especially blood) at higher temperatures, so when you introduce a soiled fabric to water, you want it to be warm.
Warm and hot water has the most cleaning power because it is speeding up the chemical reaction of the soap removing soil. The hotter water is, the more soluble most soils are and the easier they are to remove.
Washing Machine Maintenance
Washing machine maintenance is very often overlooked, but you need to take it into account when considering your water temperature habits.
Gunk builds up more easily in your washing machine with cold water which means you’ll be calling the maintenance man more often. For the same reason hot water gets dirt out of clothes more easily, it also keeps buildup out of your machine. If you are washing in cold water and using more detergent to make up for the cold, you’re creating a possible buildup situation in the machine.
On a heavily soiled garment, you can get away with warm water instead of hot 99% of the time. Using warm instead of hot will also save up to half the energy of hot water while still getting most of the soil removal benefits. If you decide to wash on cold most or all of the time, consider doing some washing machine maintenance once a month with a few hot water cycles and no clothes. You can peek inside the machine and depending on what detergent you are using you may see lots of bubbles – this is the detergent residue that is stuck in the machine coming out. You can hasten the washing machine strip by adding vinegar or Eco Nuts Liquid Detergent to the hot water which will aid in the removal of that gunk building up.
My general recommendations are to wash in a mixture of water temperatures according to what’s on your clothing labels, and sort your items accordingly. Having to buy new clothes (or having to go through the mental anguish of having to retire an old favorite because there was some kind of laundry mishap) can be more expensive or simply not worth it, depending on what you spend on clothes and how attached you are to them. Your washing machine maintenance will be taken care of automatically if you do this, as well. I generally wash on a mix of cold or warm for about 90% of my own washing. Your priorities may be different from mine – so feel free to disagree.
Now dear readers, what temperature do you wash on the most? Cold? warm? a mix?