You should wash up in the sink. It’ll use less water than the dishwasher.

Granny

The modern dishwasher has a number of programs and many will also vary their washing cycle depending on the amount of dirt they detect in the water (as do newer washing machines when you’re washing clothes). This makes it a bit harder to work out the water and energy consumption figures but let’s start with some published, generic data and see how that compares. The chances are, if we had a more up to date machine, it’ll run with lower totals than these numbers.

According to Bosch, the average washing cycle uses around 9.5 litres of water and 0.8KWh of electricity (water heating, pumping and so on). If the cycle can use less, it will – but, equally, for things that need extra oooph to clean, it could use more. Obviously, hand washing means we’re not using power to run a pump – but we still need to heat the water we’ll pour into the sink and use for rinsing.

Washing by hand is even harder to work out. First, we better assume Granny fills the sink up and washes things that way – if she’s leaving the tap running then her water consumption will be off the scale (60 litres or so is entirely possible) and there’s simply no comparison. So: Wash in one sink, stack everything to drain on the side. But what’s a typical sink hold? It’s about 20 litres. Half-fill it and we’re using about 10 litres. We’re already using about the same volume of water as the machine’s total cycle and that’s before changing the water for a clean refill if things get greasy!

Next time you wash up by hand after that light lunch, put the plug in the sink so you can monitor how much water you use. If the sink approaches half full before you’ve finished then the machine would have beaten you – and unless you washed up in cold water, it would have used about the same electrical energy, too.

Granny, we’re washing our hands of this one!