What does a washing machine (cold wash) cost to run?

Washing in cold water is one of the easiest power savings in the laundry, because in almost any washing machine the vast majority of the energy goes into heating the water, not turning the drum. Run the same load cold and you cut nearly all of that out, leaving just the small cost of the motor and pump.

That is the key thing to understand about any washing machine. The spinning, pumping and agitating use very little electricity. It is warming the water from cold to a warm or hot wash temperature that dominates the cycle, so a cold wash uses only a fraction of what the same load would cost run hot.

Modern detergents are formulated to work well in cold water, so for everyday loads of lightly soiled clothes, a cold wash gets them just as clean for a fraction of the energy. The idea that clothes need heat to come clean is largely a hangover from older detergents; today the everyday load of shirts, jeans and towels does perfectly well cold.

Front loaders use less water and spin faster than top loaders, so less drying is needed, which compounds the saving. A faster final spin wrings more water out of the clothes, which means less time in a power-hungry dryer afterwards, or a quicker turn on the line. The savings in the wash and the savings in the drying stack on top of each other.

Reserve warm or hot washes for the truly dirty loads, the nappies or bedding, and let the everyday washing run cold. Treat hot as the exception you reach for when a load genuinely needs it, not the default the dial happens to sit on, and you keep the water-heating cost for the handful of loads that actually justify it.

Because a washing machine is a load you fully control, it is also worth running full loads rather than half-empty ones and, if your machine can be timed, shifting the wash to a cheaper night rate. Put a week of washing into the calculator as cold cycles and compare it to hot, and the gap makes the case on its own.