Cold Wash vs Hot Wash: A Guide to Saving Money

The verdict, line by line

Cold washing wins, and it is not close. At the defaults of our calculator — 5 loads a week, 260 loads a year, electricity at $0.17 per kWh, 50 litres of water per load heated from 15°C — a cold wash costs $13.26 a year and a hot wash at 60°C costs $129.06 a year. The difference is $115.80 a year, or about $0.45 per load, in cold's favour. A warm wash at 40°C sits between them at $77.35 a year: it saves $51.71 against hot, but still costs $64.09 more than cold. Those three numbers are the whole verdict. Everything else in this guide is about when they change, why they are what they are, and what not to get wrong. If you wash 5 loads a week and you switch every load from hot to cold, you keep $115.80 a year for no loss of anything except hot water. If you keep hot washes only for the loads that genuinely need them — bedding after illness, cloth nappies, heavily soiled work clothes — you keep nearly all of that saving while keeping the hot wash where it earns its keep.

The physics: why heating water costs so much

The machine itself is cheap to run. In our model it uses 0.30 kWh per load for tumbling, pumping, and spinning, whatever the temperature. That is 78 kWh over 260 loads, or $13.26 a year at $0.17 per kWh — the entire cold-wash bill. A hot wash adds one more job: heating the wash water. Water is stubborn stuff. It takes 4.186 kilojoules to raise one litre by one degree, so heating 50 litres from 15°C to 60°C — a lift of 45 degrees — takes 50 times 4.186 times 45, or 9,418.5 kilojoules. Divide by 3,600 to convert kilojoules to kilowatt-hours and you get 2.62 kWh of heat per load. Add the machine's 0.30 kWh and a hot load uses 2.92 kWh, nearly ten times a cold load. Over 260 loads that is 759.2 kWh, or $129.06 a year. The lesson is general: whenever a household job involves heating water, the water is the bill and the machine is a footnote. That is why a hot wash costs ten times a cold wash while a longer cold cycle costs only a little more.

Every branch, so you can find your own household

The defaults are a starting point, not your house. At 3 loads a week, cold costs $7.96 a year and hot costs $77.44, a saving of $69.48 for cold. At 8 loads a week, cold costs $21.22 and hot costs $206.50, a saving of $185.28. Notice that the saving grows with every load: the more you wash, the more each hot load costs you, so large families gain the most from switching. Price matters just as much. At $0.30 per kWh, cold costs $23.40 a year and hot costs $227.76, a saving of $204.36 — nearly double the default saving, because the same kilowatt-hours are suddenly worth more. Water volume matters too: a machine that heats only 30 litres instead of 50 cuts the heat energy by two fifths, and the hot-wash penalty shrinks with it. Inlet temperature matters in the other direction: cold winter water entering at 5°C instead of 15°C needs a 55-degree lift to reach 60°C, not 45, so a hot wash costs more in January than in July. Put your own numbers into the calculator rather than trusting any single figure here, and the branch that matches your house is the one that counts.

The warm-wash middle ground

If cold feels like too big a jump, warm is a genuine compromise rather than a cop-out. A 40°C wash heats the same 50 litres through 25 degrees instead of 45, needing 1.45 kWh of heat, so a warm load uses 1.75 kWh in total and costs $77.35 a year at the defaults. Against hot, that saves $51.71 a year — almost half the cold saving — while still giving bedding and towels some heat. A sensible split is cold for everyday clothes and warm for bedding, towels, and anything that smells less than fresh. Suppose half your 260 loads go warm and half go cold: the yearly bill is half of $77.35 plus half of $13.26, or $45.31, saving $83.75 against all-hot. The exact split matters less than the direction: every load you move down a temperature step keeps money, and you do not need to move all of them at once.

Three mistakes to avoid

First, assuming a cold wash cannot clean. Modern detergents are formulated for cold water, and for everyday laundry — shirts, underwear, sheets, gym clothes — a cold wash with the right detergent cleans as well as a hot wash did a generation ago. The mistake is not washing cold; it is using an old detergent dosed for hot water and blaming the temperature. Second, washing hot out of habit for loads that do not need it. Towels do not need 60°C every week, and neither do jeans. Reserve hot washes for the short list that genuinely benefits: bedding after illness, cloth nappies, and heavily soiled items. Everything else can go cold or warm. Third, forgetting the dryer. A household that saves $115.80 a year by washing cold and then tumble-dries every load on high heat has moved the energy bill, not removed it. Line-drying where you can, or at least drying on a lower setting, protects the saving you just made. Avoid those three mistakes and the $115.80 is real money, not a figure on a page.

Output · formula · meaning

Who uses this

• The household switching to cold: reads the verdict and the physics, then checks its own loads and rate in the calculator.
• The large family: sees the 8-load branch at $185.28 saved and treats the switch as a real budget line.
• The warm-wash compromiser: adopts the cold-and-warm split for bedding and towels without giving up heat entirely.
• The renter with a shared laundry: uses the per-load figures — $0.05 cold versus $0.50 hot — to judge a pay-per-load machine.

Accuracy & limitations

This guide uses the same energy-only model as the calculator: 0.30 kWh of machine energy per load, 50 litres heated per hot or warm load, 52 weeks a year, and per-load energy rounded to two decimals before yearly totals. It leaves out detergent, machine wear, purchase price, and drying, and real machines vary in water use and inlet temperature. Treat every figure as the yearly energy gap at the stated settings, and put your own settings into the calculator for your household.