People argue about this in kitchens up and down the country, and both sides are sometimes right. The reason there is no single answer is that the cost of washing dishes is not really about the dishwasher or the sink. It is about the hot water, how much of it you use and how you heat it. Once you look at where the pennies actually go, the winner turns out to depend on how full the load is, which cycle you pick, and whether you leave the tap running while you scrub.
The short answer. A full dishwasher run on its eco cycle is one of the cheaper ways to clean a big batch of dishes, costing around 30 to 40p in electricity plus a tablet. Washing the same load by hand under a running hot tap is usually dearer, because a running tap gets through a lot of heated water. But washing efficiently in a bowl, with water heated by a gas boiler, can be cheaper than the dishwasher. The most expensive habit of all is a half-empty dishwasher or a running hot tap. Prices here are illustrative examples at recent cap rates.
Why it is really a hot-water question
Neither the dishwasher motor nor your hands do much to the bill. The energy goes almost entirely into heating water. Warming water is surprisingly demanding: raising one litre by one degree takes about 0.00116 kWh, so heating ten litres from a cold 10 degrees up to 50 takes roughly 0.46 kWh. That is why the number that matters is not whether you use a machine, but how many litres of hot water the job uses and what you pay to heat each one.
How you heat that water changes the price too. A gas boiler produces a unit of heat for around a third of the price of a unit of electricity, so hot water drawn from a gas-heated cylinder or combi is cheap, while a dishwasher heats its own water with an electric element at the full electricity rate. That single difference explains most of the surprises in this comparison, and it is why the same wash can be cheap in one house and dear in another. Our hot water savings guide goes deeper into what heating water actually costs.
What a dishwasher actually costs per cycle
A modern dishwasher heats a small, fixed amount of water very efficiently and reuses it by spraying it around, which is why it gets through far less water than most people expect, often only around ten litres for a full load. The energy used depends heavily on the programme.
| Dishwasher cycle | Electricity used | Cost in electricity |
|---|---|---|
| Eco cycle (longer, cooler) | ~0.8 to 1.0 kWh | ~21p to 26p |
| Auto or normal cycle | ~1.2 to 1.5 kWh | ~31p to 39p |
| Intensive or hot cycle | ~1.6 to 1.8 kWh | ~42p to 47p |
At an example electricity price of 26.11p per kWh. Add roughly 10p to 15p for a tablet, plus a small amount for water if you are on a meter. Actual figures vary by model and load.
The eco cycle is the cheapest despite taking longer, because it heats the water less and holds it at a lower temperature for a good soak instead. The catch is that a dishwasher costs almost the same to run whether it is full or half empty, so a barely filled machine multiplies the cost per plate. The single most effective saving is simply to wait until it is properly full. The dishwasher eco mode explained and dishwasher efficiency guides cover how to get the lowest cost per wash.
What washing up by hand costs
Hand washing has a huge range, and the difference is almost all down to whether the hot tap runs while you work. Left running, a kitchen tap delivers something like six litres a minute, much of it heated. Six minutes of that is over thirty litres of hot water, which needs well over a kilowatt hour of heat to warm.
Fill a bowl instead and the picture changes completely. A washing-up bowl holds around six litres, and if you wash a full sink of dishes in one bowl of hot water with a quick rinse, you might use eight to twelve litres in total rather than thirty or forty. Here is roughly what each approach costs to heat, shown for both gas-heated and electrically heated water, because that choice matters as much as the method.
| Hand-washing method | Hot water used | Heated by gas | Heated by electricity |
|---|---|---|---|
| Bowl wash, careful | ~8 litres | ~3p | ~10p |
| Two bowls (wash and rinse) | ~14 litres | ~5p | ~17p |
| Running hot tap, ~6 minutes | ~30 litres | ~11p | ~36p |
Assumes water heated by about 40 degrees. Gas figures at an example 7.33p per kWh allowing for boiler losses; electricity at 26.11p per kWh. Illustrative examples.
The running tap is the expensive villain here, especially if your hot water comes from electricity, where it can cost more than a full dishwasher load. A careful bowl wash with gas-heated water, by contrast, is about the cheapest way to clean dishes there is.
The head-to-head, load for load
To compare fairly you have to wash the same pile of dishes both ways. A full dishwasher holds roughly what you would clean in two or three bowls of hand washing, so line those up. On the eco cycle the dishwasher costs around 26p in electricity plus a tablet, call it 38p all in. The same quantity done in two bowls of gas-heated water costs only a few pence to heat, plus a squirt of washing-up liquid. Done under a running electric-heated tap, the hand wash could cost 40p or more, level with or above the dishwasher.
So the ranking, cheapest first, tends to run: an efficient bowl wash with gas-heated water, then a full dishwasher on eco, then a running-tap hand wash, with a half-empty dishwasher and a running electric-heated tap sharing the bottom of the table. The machine is not automatically the frugal choice, but it is far more consistent than hands, which swing from very cheap to very dear depending on the tap. If you want to measure your own habits, a plug-in energy monitor will read the dishwasher directly, and the appliance running cost calculator turns any kWh figure into pence.
When hand washing wins
Hands come out cheapest in a few clear situations. The first is a small amount of washing up: a couple of mugs and plates do not justify a whole dishwasher cycle, and a splash of hot water in a bowl deals with them for pennies. The second is a home with gas-heated hot water, where the water going into the bowl is cheap to warm, so a disciplined bowl wash undercuts the electric heating inside a dishwasher.
The trick, in both cases, is technique. Do not let the hot tap run. Fill a bowl, wash from cleanest to dirtiest so the water lasts, scrape plates rather than rinsing them under the tap, and rinse in a second bowl or a quick cold splash rather than a hot stream. Done that way, hand washing is genuinely economical. Done with the tap gushing hot water throughout, it quietly becomes one of the more expensive things you do in the kitchen.
When the dishwasher wins
The machine takes the lead when you are washing a lot at once and you run it properly. Its efficiency comes from using very little water for the number of items it cleans, so a full load spreads that fixed cost of heating across a big pile of dishes. It also washes at a high temperature that hands cannot tolerate, which many people value for hygiene, and it saves a chunk of time and effort that has its own worth.
To get the win, three habits matter. Run it only when it is full, since a half load costs almost the same as a full one. Choose the eco programme, which uses the least energy despite the longer run time. And skip pre-rinsing plates under a hot tap, because that can waste more hot water than the entire cycle uses; scraping is enough. If you are on a time-of-use tariff, running it in a cheap overnight window trims the cost further, in the same way that shifting the washing machine saves money.
Getting the cost down whichever you choose
Because the whole bill is hot water, the savings are the same on both sides of the sink. Turn the tap off while you scrub. Wash in a bowl rather than under a running stream. Only run a full dishwasher, and run it on eco. If your hot water comes from an electric immersion, heating it on an off-peak rate makes every wash cheaper, a point covered in the immersion heater cost guide, and a well-lagged cylinder keeps that heat for longer. Fitting an aerating tap or being handy with a low-flow fitting elsewhere cuts the litres too.
None of these choices moves the needle as much as heating and driving do, so it is not worth losing sleep over a few pence a wash. But the habits are free, they compound over hundreds of washes a year, and they matter most in the homes where hot water is heated by expensive electricity rather than cheaper gas.
The verdict
There is no blanket winner, because the cost lives in the hot water, not the method. A full dishwasher on eco is cheap, consistent and hard to beat for a big batch, costing around 30 to 40p all in. An efficient bowl wash with gas-heated water is cheaper still for smaller amounts. The expensive options are the ones that waste hot water: a half-empty dishwasher, or a hand wash under a running electric-heated tap, either of which can cost more than doing it the sensible way.
Pick the method that suits the size of the job, keep the dishwasher full and on eco, keep the tap off when you wash by hand, and you will be near the cheapest cost either way. For the wider picture on what your appliances and hot water are costing, the washing at 30 degrees guide and the main home electricity section carry the rest.