# Cold Wash Laundry Savings Calculator What washing in cold water saves, computed from the temperature rise and your water heater's efficiency. --- - **Canonical URL:** https://dothecalculation.com/calculators/cold-wash-laundry-savings-calculator - **Category:** Eco & Sustainability - **Publisher:** Do The Calculation (https://dothecalculation.com) - **Cost:** Free, no account or sign-up required - **Privacy:** Runs entirely in the browser; inputs are never sent to a server - **Methodology:** https://dothecalculation.com/methodology --- ## Calculate What Washing in Cold Water Saves Energy computed from the temperature rise and your water heater's efficiency, so the answer changes with the season, the machine and how your water is heated. - Works from the physics of heating water, not a fixed kWh-per-load figure - Handles electric resistance, gas and heat pump water heaters - Shows what share of a hot load is heating rather than washing ## 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](/calculators/appliance-energy-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](/calculators/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](/calculators/appliance-energy-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](/calculators/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](/calculators/led-bulb-savings-calculator) covers the other classic no-cost household energy change, and the [Carbon Footprint Calculator](/calculators/carbon-footprint-calculator) puts the avoided kilograms into the context of a whole household. ## 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. ## 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. ## Related guides - [Appliance Energy Cost Guide: Watts, kWh, and Monthly Bills](https://dothecalculation.com/blog/green/appliance-energy-cost-estimation) — Estimate appliance electricity cost from wattage, hours per day, utility rate, and the live DTC appliance energy calculator logic. - [How to Use Do The Calculation Calculators: A Practical Step-by-Step Guide](https://dothecalculation.com/blog/site-guides/how-to-use-calculators) — Learn the fastest reliable workflow for using Do The Calculation calculators, reading results, checking formulas, and using save, print, share, and export actions correctly. ## Related calculators - [Water Heater Efficiency & Lifetime Cost Calculator](https://dothecalculation.com/calculators/water-heater-efficiency-calculator) — Compare standard electric, gas, and hybrid heat pump water heaters to evaluate lifetime operating costs, payback, and carbon footprints. - [Heat Pump COP & Energy Savings Calculator](https://dothecalculation.com/calculators/heat-pump-savings-calculator) — Compare conventional heating systems with heat pumps to calculate annual utility savings, efficiency gains, and carbon emission offsets. - [Smart Thermostat HVAC Run-Time & Cost Savings Calculator](https://dothecalculation.com/calculators/smart-thermostat-savings-calculator) — Estimate heating and cooling cost reductions, HVAC runtime hours saved, and carbon offsets from smart thermostat temperature setbacks. - [Double Pane Window Retrofit ROI & Payback Calculator](https://dothecalculation.com/calculators/double-glazing-payback-calculator) — Calculate heating and cooling energy loss reduction, fuel cost savings, and payback period for double pane or Low-E window retrofits. - [Variable Speed Pool Pump ROI & Utility Savings Calculator](https://dothecalculation.com/calculators/energy-efficient-pool-pump-calculator) — Apply pump affinity laws to calculate energy savings, electric utility bill offsets, and payback period for variable speed pool pumps. - [Geothermal Heat Pump Installation ROI & Payback Calculator](https://dothecalculation.com/calculators/geothermal-hvac-payback-calculator) — Compare geothermal COP against standard heating and cooling systems to project annual utility savings, incentives, and payback. --- _Every kWh and dollar figure on this page was produced by running this calculator with the stated inputs rather than estimated. The model computes the heat required from mass, specific heat and temperature rise, and assumes the machine reaches and holds the temperature set — many machines run several degrees below their labels, so a specific machine can differ. Pipe, drum and standby heat losses are ignored, which makes the estimate conservative. Heater efficiency carries a lot of weight: electric resistance is near 0.95, gas 0.60 to 0.80 on recovery, and a heat pump 2 to 4 as a coefficient of performance. Detergent cost and the value of longer garment life are outside the calculation._ --- _Source: [Do The Calculation](https://dothecalculation.com/calculators/cold-wash-laundry-savings-calculator). Quote freely with attribution and a link to this page._