What is the eco programme on a washing machine actually doing?

The eco programme confuses people because it is the longest cycle on the machine and yet is presented as the efficient one. Both are true, and for the same reason. Almost all the electricity a washing machine uses goes into heating water, not into turning the drum. Running the motor for three hours costs very little; heating the water twenty degrees hotter costs a lot. So the cheapest wash is a long, cool one.

What you'll need

• The programme table in your manual, if you want your machine's actual figures

Step by step

1. Understand where the energy actually goes.Heating the water accounts for the large majority of a wash's electricity. The motor, the pump and the electronics are a small fraction. This one fact explains every design decision in an eco cycle.
2. Accept that eco 40-60 does not mean 40 to 60 degrees.It is a standardised test programme name. In use, many eco cycles peak well below their nominal temperature — sometimes in the high twenties or thirties on an eco 40. The manufacturer is not cheating; the programme is designed to clean by time rather than heat.
3. Recognise the trade you are making.You save electricity and some water, and you spend two to four hours of machine time. If the machine is otherwise idle, that is a good trade. If you have four loads to get through this evening, it is not.
4. Use it for ordinary soil.Everyday clothing, lightly worn, normal grime and body oils. Long low-temperature soaking with a good detergent handles all of it.
5. Do not use it where temperature is the point.Bedding after illness, nappies, heavily soiled workwear, towels that have gone sour, or a household with someone immunosuppressed. Those want a genuine 60 degree cottons cycle, and an eco programme will not deliver it.
6. Use liquid or gel detergent on long cool cycles.Powders, particularly those containing oxygen bleach, need warmth to dissolve and activate properly. On a cool eco cycle a powder can leave residue and underperform.
7. Do not shorten it with a time-saver option.The length is the mechanism. Adding a time-saver to an eco cycle removes exactly the thing that was substituting for heat, and you get a cool short wash that cleans poorly.
8. Run a hot maintenance cycle periodically if you mostly wash eco.A machine that never goes above thirty degrees grows a biofilm in the seal, drawer and hoses. An empty hot cycle once a month is what prevents the smell that low-temperature washing otherwise guarantees.

Tips

• If you are on a time-of-use tariff, an eco cycle started on a delay timer to run in the cheap window is the largest single saving available on laundry electricity.
• Eco programmes usually assume a reasonably full drum. Running one nearly empty removes most of the efficiency argument for it.
• If your machine has both an eco cycle and a separate cotton eco, check the manual — they often differ in maximum load and in whether the temperature is genuinely reached.

Common mistakes

• Trusting the eco 60 setting for hygienic washing — It may never reach 60 degrees. If the reason for washing hot is disinfection rather than dirt, use a standard cottons 60 and accept the cost.
• Never washing hot at all — The machine itself needs heat periodically. Households that only ever run eco cycles are the ones whose machines start to smell, because nothing ever gets warm enough to break down the residue in the seal and hoses.

Questions people ask