green calculator

Cold Wash Laundry Savings Calculator

What washing in cold water saves, computed from the temperature rise and your water heater's efficiency.

Water heating is 96% or more of a hot wash, and the energy is litres x temperature rise x 4.186 / 3600 / heater efficiency. A 57-litre load heated from 15 C to 49 C costs 2.46 kWh against 0.44 kWh cold — a saving of 2.02 kWh per load. Six loads a week with 60% washed warm saves 379 kWh and $64 a year on electric heating, but only about $24 with a heat pump water heater.

Quick actions: Save inputs, view saved runs, print, share, or export results

Saved Runs

Inputs

Water heater

Loads Per Week

Water Per LoadL

Hot Wash Temp°C

Cold Wash Temp°C

Inlet Temp°C

Energy Price$/kWh

Machine Electricity Per LoadkWh

Share Currently Washed Hot%

Grid Intensitykg CO2/kWh

Results

Annual Saving

$64.39

Annual kWh Saved379 kWh

Saving Per Load2.023 kWh ($0.34)

Hot Load Energy2.462 kWh

Cold Load Energy0.439 kWh

Heating Share of a Hot Load96.3%

Temperature Rise (hot)34 °C

Temperature Rise (cold)5 °C

Loads Per Year312

Currently Washed Hot187 loads

Current Annual Energy516 kWh ($87.66)

All-Cold Annual Energy137 kWh ($23.28)

Ten-Year Saving$643.87

CO2 Avoided Per Year140.5 kg

Tip

Worth running once: the answer depends heavily on how your water is heated, and a heat pump water heater changes it by more than a factor of two.

Formula

Water heating energy

Heat energy (kWh) = litres x temperature rise (C) x 4.186 / 3600 / heater efficiency

  4.186   specific heat of water, kJ per kg per C
  3600    kJ per kWh
  1 litre of water = 1 kg

Hot load  = heat(hot temp - inlet) + machine kWh
Cold load = heat(cold temp - inlet) + machine kWh
Saving per load = hot load - cold load

Heater efficiency: electric resistance 0.95 | gas 0.70 recovery | heat pump 2.6 COP

The energy depends on the temperature rise, not the wash temperature on its own — which is why the same setting costs meaningfully more in winter than in summer. Heater efficiency divides into the result, and a heat pump with a coefficient of performance above 1 delivers more heat than the electricity it draws. That produces the counter-intuitive conclusion that the more efficient your water heating already is, the less washing cold saves you.

Step by step

How the calculation works

1Enter loads per week and litres per load. A modern front-loader uses 45 to 60 litres; an older top-loader can use 120 or more, which roughly doubles every figure here.
2Inlet temperature is the input most people skip. Mains water arrives at roughly 10 to 15 °C in winter and 18 to 25 °C in summer in temperate climates, and the energy scales directly with the gap you have to close.
3Heater type matters more than anything except the temperature. Electric resistance heating has the most to gain from switching to cold; a heat pump water heater has already captured most of that benefit at the tank, which cuts the saving to roughly a third.
4Set the rinse to cold regardless of the wash setting. Rinsing only removes detergent, so warmth achieves nothing and is pure waste.
5If you wash exclusively cold in a front-loader, run an occasional hot cycle to keep biofilm out of the gasket and drum. The [appliance energy cost calculator](/calculators/appliance-energy-calculator) covers the rest of the machines in the house on the same basis.

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Cold Wash Laundry Savings Calculator

What washing in cold water saves, computed from the temperature rise and your water heater's efficiency.

Quick actions: Save inputs, view saved runs, print, share, or export results

Saved Runs

Inputs

Water heater

Loads Per Week

Water Per LoadL

Hot Wash Temp°C

Cold Wash Temp°C

Inlet Temp°C

Energy Price$/kWh

Machine Electricity Per LoadkWh

Share Currently Washed Hot%

Grid Intensitykg CO2/kWh

Results

Annual Saving

$64.39

Annual kWh Saved379 kWh

Saving Per Load2.023 kWh ($0.34)

Hot Load Energy2.462 kWh

Cold Load Energy0.439 kWh

Heating Share of a Hot Load96.3%

Temperature Rise (hot)34 °C

Temperature Rise (cold)5 °C

Loads Per Year312

Currently Washed Hot187 loads

Current Annual Energy516 kWh ($87.66)

All-Cold Annual Energy137 kWh ($23.28)

Ten-Year Saving$643.87

CO2 Avoided Per Year140.5 kg

Tip

Worth running once: the answer depends heavily on how your water is heated, and a heat pump water heater changes it by more than a factor of two.

Summary

Key output metrics

Annual Saving

$64.39

379 kWh a year, $643.87 over ten years

Per Load

2.02 kWh

$0.34 saved on every load switched from hot to cold

Heating Share of a Hot Load

96.3%

2.46 kWh hot against 0.44 kWh cold

D3 visualization

Energy Per Load by Wash Temperature

The same machine and inlet temperature across a range of wash settings. Energy scales with the temperature rise, so the saving comes from the gap you avoid closing.

Guide

How to understand and use this calculator

Quick Answer — How Much Does Washing in Cold Water Save?

Nearly all the energy a washing machine uses goes into heating water. The motor, pump and controls draw very little. So the saving from washing cold is the heating you avoid, and that follows straight from physics:

Energy (kWh) = litres × temperature rise (°C) × 4.186 ÷ 3,600 ÷ heater efficiency

The 4.186 is the specific heat of water in kilojoules per kilogram per degree, 3,600 converts kilojoules to kilowatt-hours, and one litre of water weighs one kilogram.

A 57-litre load heated from a 15 °C inlet to a 49 °C warm wash is a 34-degree rise. That is 57 × 34 × 4.186 ÷ 3,600 = 2.25 kWh of heat, or 2.37 kWh through a 95%-efficient electric heater. Add 0.09 kWh for the machine itself and a hot load costs 2.46 kWh.

The same load washed at 20 °C needs only a 5-degree rise: 0.35 kWh of heating plus 0.09 for the machine, or 0.44 kWh total.

The difference is 2.02 kWh per load, and 96.3% of a hot load is water heating. At 17 cents a kWh that is 34 cents saved per load.

How to Use This Calculator: A Household of Two or Three

Enter loads per week and litres per load. A modern front-loader uses 45 to 60 litres; an older top-loader can use 120 or more, which roughly doubles every figure on the page.

The inlet temperature is the input most people skip and it matters a great deal. Mains water arrives at roughly 10 to 15 °C in winter and 18 to 25 °C in summer in temperate climates, and the saving scales directly with the gap you have to close.

For 6 loads a week at 57 litres, a 49 °C warm wash against a 20 °C cold, a 15 °C inlet, a 95%-efficient electric heater, electricity at $0.17, and 60% of loads currently washed warm:

Hot load 2.46 kWh, cold load 0.44 kWh, saving 2.02 kWh per switched load
312 loads a year, of which 187 are currently warm
Current annual use 515.7 kWh costing $87.66
All-cold annual use 136.9 kWh costing $23.28
Saving: 378.7 kWh and $64.39 a year, or $644 over ten years, avoiding 140.5 kg of CO2 on an average grid

That is a real saving from a setting change that costs nothing. The appliance energy cost calculator covers the rest of the machines in the house on the same basis.

A Second Example: Two Things That Change the Answer

First, a larger household washing hotter. 10 loads a week at 68 litres, washing at 60 °C against a 10 °C inlet, all loads currently hot, electricity at $0.24. The temperature rise is 50 degrees, so a hot load costs 4.27 kWh against 0.94 kWh cold — a saving of 3.33 kWh per load, and 97.4% of a hot load is heating.

Across 520 loads a year that is 1,731 kWh and $415.49 a year saved, $4,155 over ten years, avoiding 692 kg of CO2. Six times the first household's saving, from a household doing under twice the laundry — because both the temperature rise and the electricity price are higher.

Second, and in the opposite direction: change the heater. Run the *first* household's numbers through a heat pump water heater with a coefficient of performance of 2.6 and the hot load falls from 2.46 kWh to 0.96 kWh, because the heater moves heat rather than making it. The saving per load drops to 0.74 kWh and the annual saving from $64.39 to $23.53 — barely a third.

That is the counter-intuitive result worth knowing. The more efficient your water heating, the less washing cold saves you. A household on electric resistance heating has the most to gain; one with a heat pump has already captured most of the benefit at the tank. The same logic applies to gas, where a recovery efficiency around 0.70 and a much lower price per unit of energy change both sides of the sum at once.

Does Cold Water Actually Clean?

For most household laundry, yes. Detergent chemistry has changed substantially: modern formulations contain enzymes selected to work at low temperatures, and cold-specific detergents are formulated around 15 to 20 °C rather than adapted to it. Independent testing consistently finds cold washes remove ordinary body soil, food and everyday dirt to a standard most people cannot distinguish from a warm wash.

Cold water is also better for the fabric. Heat is what drives shrinkage, dye bleeding and fibre degradation, so cold washing extends garment life — which for most wardrobes is worth considerably more than the electricity saving.

Three situations still justify heat. Heavy grease and oil need warmth to dissolve; cold water leaves oil-based stains in the fabric. Sanitising — clothing from someone with an infection, cloth nappies, kitchen textiles handled after raw meat — needs temperatures above about 60 °C to reliably reduce microbial load, and this is a genuine hygiene reason rather than a habit. And heavily soiled workwear simply cleans better warm.

One practical warning about washing exclusively cold: front-loading machines can develop biofilm and odour in the gasket and drum when they never run warm. An occasional hot cycle, empty or with towels, keeps that under control. It costs a couple of loads worth of energy a month and prevents a problem that is unpleasant and hard to reverse.

The rinse temperature is a separate setting on many machines and always worth setting to cold. Rinsing warm cleans nothing — it only removes detergent — and it is pure waste. Where a machine has a heater built in rather than drawing hot water from the house supply, the Energy Star appliance savings calculator is the better tool for comparing whole machines.

Limitations

The model calculates the energy needed to raise the water temperature, which assumes the machine actually reaches and holds the temperature you set. Many machines do not: the actual wash temperature is often several degrees below the label, some models blend hot and cold to hit a target, and internal-heater machines behave differently again from those drawing pre-heated water from a tank. That means the real figure for a specific machine can differ from this by a meaningful margin.

Heat losses are ignored. Water cools in the pipe run between heater and machine, the drum and its contents absorb heat, and a tank heater has standby losses running continuously regardless of use. Including those would raise the hot-wash figure and therefore the saving, so this estimate is conservative on that count.

The heater efficiency input carries a lot of weight and is easy to enter wrongly. Electric resistance is near 0.95 to 0.98, a modern gas heater around 0.60 to 0.80 on recovery efficiency, and a heat pump has a coefficient of performance of 2 to 4, meaning it delivers more heat than the electricity it consumes. Gas also needs its price converted into dollars per kWh of delivered energy before the comparison is meaningful — a therm is 29.3 kWh, so gas at $1.50 a therm is about 5.1 cents per kWh before efficiency.

Finally, this prices energy only. It does not account for detergent cost, which can be marginally higher for cold-specific formulations, nor for the value of longer garment life, which for most households substantially exceeds the electricity saving and is the better argument for cold washing anyway.

Related Calculators

The Appliance Energy Cost Calculator applies the same watts-to-dollars logic across every machine in the house, which is the natural next step once the washer is settled. The Energy Star Appliance Savings Calculator compares whole machines rather than settings, and is the right tool when the washer itself is due for replacement. The LED Bulb Savings Calculator covers the other classic no-cost household energy change, and the Carbon Footprint Calculator puts the avoided kilograms into the context of a whole household.

Related concepts

Specific Heat of Water

4.186 kilojoules to raise one kilogram of water by one degree Celsius. It is the constant behind every water-heating calculation, and it is why the temperature rise, not the temperature itself, determines the energy.

Coefficient of Performance (COP)

How many units of heat a heat pump delivers per unit of electricity consumed, typically 2 to 4. Values above 1 are possible because the device moves ambient heat rather than creating it, which is why heat pump water heating changes this calculation so much.

Inlet Temperature

The temperature of mains water arriving at the machine, roughly 10 to 15 °C in winter and 18 to 25 °C in summer in temperate climates. The energy needed depends on the gap between it and the wash temperature, not on the wash temperature alone.

Frequently Asked Questions

How much does washing in cold water save?+

For a household doing six loads a week with electric water heating and 60% currently washed warm, about 379 kWh and $64 a year. A larger household washing all loads hot at a higher electricity rate saved $415 a year in the second worked example. The range is wide because the inputs vary so much.

How much of a washing machine's energy goes into heating water?+

Around 96% for a warm wash and over 97% for a hot one. The motor, pump and controls draw well under a tenth of a kilowatt-hour per load. That is why the wash temperature is essentially the only setting that matters for energy.

Does washing in cold water actually clean clothes?+

For everyday laundry, yes. Modern detergents contain enzymes selected to work at 15 to 20 °C, and independent testing finds cold washes handle ordinary body soil, food and dirt to a standard most people cannot distinguish. Heavy grease, sanitising and heavily soiled workwear are the genuine exceptions.

Why does a heat pump water heater reduce the saving?+

Because it moves heat rather than generating it, delivering two to four units of heat per unit of electricity. In the worked example a heat pump cut the annual saving from $64 to $24 — the household had already captured most of the benefit at the tank, so switching to cold adds less.

Does the season change the answer?+

Yes, noticeably. Mains water arrives at roughly 10 to 15 °C in winter and 18 to 25 °C in summer in temperate climates, and the energy scales directly with the gap you have to close. Winter washes cost meaningfully more to heat than summer ones.

Should I set the rinse to cold too?+

Always. Rinsing only removes detergent, so warmth achieves nothing at all, and it is one of the purest forms of wasted energy in a household. Many machines set the rinse separately from the wash.

Will washing only in cold cause smells in my machine?+

It can, in front-loaders, where biofilm builds up in the gasket and drum when the machine never runs warm. An occasional hot cycle — empty or with towels — prevents it, at the cost of a couple of loads worth of energy a month.

Does cold washing help clothes last longer?+

Yes, and for most households this is worth more than the electricity. Heat is what drives shrinkage, dye bleeding and fibre breakdown, so cold washing extends garment life. This calculator prices only the energy, so it understates the real benefit.

Formula

Water heating energy

Heat energy (kWh) = litres x temperature rise (C) x 4.186 / 3600 / heater efficiency

  4.186   specific heat of water, kJ per kg per C
  3600    kJ per kWh
  1 litre of water = 1 kg

Hot load  = heat(hot temp - inlet) + machine kWh
Cold load = heat(cold temp - inlet) + machine kWh
Saving per load = hot load - cold load

Heater efficiency: electric resistance 0.95 | gas 0.70 recovery | heat pump 2.6 COP

Step by step

How the calculation works

1Enter loads per week and litres per load. A modern front-loader uses 45 to 60 litres; an older top-loader can use 120 or more, which roughly doubles every figure here.
2Inlet temperature is the input most people skip. Mains water arrives at roughly 10 to 15 °C in winter and 18 to 25 °C in summer in temperate climates, and the energy scales directly with the gap you have to close.
3Heater type matters more than anything except the temperature. Electric resistance heating has the most to gain from switching to cold; a heat pump water heater has already captured most of that benefit at the tank, which cuts the saving to roughly a third.
4Set the rinse to cold regardless of the wash setting. Rinsing only removes detergent, so warmth achieves nothing and is pure waste.
5If you wash exclusively cold in a front-loader, run an occasional hot cycle to keep biofilm out of the gasket and drum. The [appliance energy cost calculator](/calculators/appliance-energy-calculator) covers the rest of the machines in the house on the same basis.

Related guides

Learn more about this calculation

Guide

Cold Wash Laundry Savings Calculator

Inputs

Results

Water heating energy

How the calculation works

Learn more about this calculation

Appliance Energy Cost Guide: Watts, kWh, and Monthly Bills

How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide

Appliance Energy Cost Calculator

Energy Star Appliance Savings Calculator

LED Bulb Savings Calculator

Key facts

Cold Wash Laundry Savings Calculator

Inputs

Results

Key output metrics

Energy Per Load by Wash Temperature

How to understand and use this calculator

Quick Answer — How Much Does Washing in Cold Water Save?

How to Use This Calculator: A Household of Two or Three

A Second Example: Two Things That Change the Answer

Does Cold Water Actually Clean?

Limitations

Related Calculators

Related concepts

Frequently Asked Questions

Water heating energy

How the calculation works

Learn more about this calculation

Appliance Energy Cost Guide: Watts, kWh, and Monthly Bills

How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide

Appliance Energy Cost Calculator

Energy Star Appliance Savings Calculator

LED Bulb Savings Calculator

Key facts

Key output metrics

Energy Per Load by Wash Temperature

How to understand and use this calculator

Quick Answer — How Much Does Washing in Cold Water Save?

How to Use This Calculator: A Household of Two or Three

A Second Example: Two Things That Change the Answer

Does Cold Water Actually Clean?

Limitations

Related Calculators

Related concepts

Frequently Asked Questions