Is it cheaper to wash dishes by hand or with a dishwasher?
The results are in, and there's a clear winner to this question. Unless you're a master of washing dishes with very little water (boat enthusiasts, anyone?), your dishwasher will probably save you money. But it does depend on how you heat your water, the cost of gas/electricity and your washing habits. Here's what we found.
Hand washing vs dishwasher
Which is cheaper? We compared the cost of energy used to run a full dishwasher to the cost of heating water for hand washing.
Running one load in a typical energy-efficient dishwasher on eco cycle uses 0.73 kWh of electricity. At a cost of 36p/kWh for electricity, each dishwasher load would cost £0.26 to run.
Hand washing could cost more or less, largely depending on how much water you use when hand washing. Do you keep the tap on hot and high, running straight for minutes on end? Or are you super efficient (or downright stingy) with water?
Gas-heated hot water
Someone very stingy with the water who only runs the tap for 3 minutes and uses 30 litres of warm water would spend an estimated £0.10 to heat that water (assuming gas-heated hot water). In this case, the hand washer saves 16p, reducing energy costs by more than 60%. However, it could be pretty hard to use such a small amount of water, because we're not talking about dishes from one meal but an entire dishwasher full of dishes.
Someone who ran the tap for 15 minutes to hand wash enough dishes to fill a dishwasher would spend around £0.52 on energy to heat the water. In this case, hand washing costs twice as much as running a load in the dishwasher. For a household running the dishwasher every other day, these hand washing habits would cost an extra £47 per year vs using a dishwasher.
What's the 'breakeven' spot? If someone runs the tap for hand washing for 7.5 minutes to wash enough dishes to fill a dishwasher, then the energy costs are equivalent for hand washing and using a dishwasher. They can either hand wash or use the machine, it would cost the same either way.
The table below shows the cost to heat water to 40 degrees Centigrade, for different water flow times. Learn more about how we calculated the litres used and the energy required to heat the water in the methodology section below.
| Cost of hot water for hand washing dishes (gas-heated water e.g. boiler) | |||||
|---|---|---|---|---|---|
| Minutes of running water | 3 | 5 | 7 | 10 | 15 |
| Litres used | 30 | 50 | 70 | 100 | 150 |
| Pt (power used to heat the water, in kWh) | 1.05 | 1.74 | 2.44 | 3.48 | 5.23 |
| 10% upward adjustment to Pt used (because gas is less efficient) | 1.15 | 1.92 | 2.68 | 3.83 | 5.75 |
| Cost (at 9p/kWh for gas) | £0.10 | £0.17 | £0.24 | £0.34 | £0.52 |
Electricity-heated hot water
For those heating their water with electricity, the dishwasher is clearly the cheaper way to go. As mentioned above, the typical dishwasher load uses 0.73 kWh at a cost of £0.26 (assuming a cost of electricity of 36p/kWh). But hand washing those dishes would cost more, even for someone who only runs the tap for just 3 minutes—using electricity to heat that water would cost £0.38 or 46% more.
Someone running the tap for 15 minutes for a leisurely hand washing session would spend £1.88 to heat the water if they use electricity-heated water. For a household running the dishwasher every other day, these hand washing habits would cost an extra £296 per year vs using a dishwasher.
| Cost of hot water for hand washing dishes (electricity-heated water e.g. electric water heater) | |||||
|---|---|---|---|---|---|
| Minutes of running water | 3 | 5 | 7 | 10 | 15 |
| L (litres used) | 30 | 50 | 70 | 100 | 150 |
| Pt (power used to heat the water, in kWh) | 1.05 | 1.74 | 2.44 | 3.48 | 5.23 |
| Cost (at 36p/kWh for electricity) | £0.38 | £0.63 | £0.88 | £1.25 | £1.88 |
Tips for saving money washing dishes by hand
Think you can't hand wash a dishwasher load of dishes with only 3 minutes of running water? Think again! Taking some tips from my mother, who spent quite a bit of time washes dishes by hand on a boat (where there is limited fresh water in the tanks), here are some ideas for using as little water as possible to wash dishes:
- Scrape. Scrape plates clean(ish) into bin before washing
- Use a dish tub. And only fill it partway, so if you have to change the water at some point, you're dumping as little water as possible
- Wash cleanest to dirtiest. Start by washing the cleanest dishes first (e.g. water glasses) and ending on the messiest (e.g. dinner plate with remains of a curry dinner)
- Sponge off before dunking. Sponge off messy dishes before dunking them in the wash basin (to keep the water as clean as possible for as long as possible). You can even use a second small dish tub (e.g. cup filled with soapy water) for dunking and cleaning the sponge between swipes to keep your main dish tub water cleaner
- Wash in batches. Stack the clean, soapy dishes in the sink next to the dish tub and rinse them together in batches (uses less water as you only have to rinse your hands once per batch not per dish)
- Wash hot but rinse colder. We need pretty warm water to wash (especially to get rids of oils/fats) but you can rinse in colder water to save energy
- Low flow. When washing or rinsing under running water, don't have the tap on too high—a low-to-medium flow might suffice and use less water. And turn off when not actively using the flow.
Also, be careful about using too many dishes per day. For example, use one plate for salad and main instead of using a side plate for the salad. Or reuse one glass for water throughout day (not one glass per meal).
Assumptions
To carry out this analysis, we had to make some assumptions, for example on water flow. We turned on our tap water on a medium flow that we thought would be pretty typical for dishwashing and tested how long it took to fill up a 1 litre bottle: 6 seconds. That's equivalent to flow of 10 litres per minute. Of course, some people might have their tap on higher, some lower.
- Medium flow (6 seconds to fill one litre)
- Water used for hand washing is heated to 40 degrees Centigrade
- Cost of electricity is 36p/kWh (this is our rough estimate for electricity prices at the end of 2022)
- Formula to calculate Pt, the power used to heat the water for hand washing, is (litres x temperature change) x 4.18 / 3600, where the temperature change is 30 (from 10 degree mains water to 40 degree washing water)