Hand Washing vs the Dishwasher – Which is Better?

From Marjory Wildcraft’s Grow Your Own Groceries.

Is it More Efficient to Hand Wash or Use the Dishwasher?

Cooking from scratch is an integral part of preparing meals from your home food pantry. Unfortunately, cooking from scratch also means extra dirty dishes, pots and pans! Recently I read an article on the U.S. Government’s ENERGY STAR web site that claimed, “If you wash dishes by hand you are wasting more then just time…” (https://www.energystar.gov/index.cfm?c=dishwash.pr_handwash_dishwash; January 31, 2016)

I thought I would double-check this claim, which is based on the ideas that using the dishwasher saves money and time, provides better cleaning results, saves energy and water, and so helps to save the environment. This caught my attention because while today’s dishwashers use less water than older models, they also run longer to make up for using less water. For example, our new dishwasher uses 2.5 – 6.4 gallons of water to run a load instead of the 7.0 gallons our old dishwasher used. However, our new dishwasher runs nearly an hour longer at 130 – 135 minutes per load instead of 76 minutes! What’s more, run time estimates assume that the hot water arrives in the dishwasher already heated to 120 degrees F. If the water arrives at a cooler temperature, our new dishwasher runs even longer to heat the water before washing.

The Cost of Running the Dishwasher

The yellow energy tag that came with our dishwasher states that we can expect to spend $25 a year on electricity and/or natural gas if we run four normal loads of dishes per week. This works out to around $0.12 per load for electricity and/or natural gas, assuming that our hot water supply consistently delivers water at the required 120 degrees F. For our calculations, we assume that normal loads use around 5 gallons of water since we only run full loads. A quick look at our utility rates shows that the cost for 5 gallons of water and sewer is currently $0.03 in our region. This means that we can reasonably estimate a cost of around $0.15 per load to run the new dishwasher.

If conserving water is the most important thing, washing dishes by hand can conserve heated water as effectively as a dishwasher if about the same amount of heated water is used for either approach. When this condition is met, washing dishes by hand will always save energy over running the dishwasher for two reasons; (1) washing dishes by hand eliminates the use of electricity to run the dishwasher and (2) hardly anyone will hand wash dishes in water as hot as 120 degrees F! Most people like dish washing temperatures to be similar to the temperature of a hot bath, around 100 degrees F. This second reason is often overlooked.

The Cost of Hand Washing Dishes

If the groundwater is at 60 degrees F, this means we heat the water by 40 degrees F to hand wash dishes instead of heating it 60 degrees F to wash dishes in the dishwasher. Using the calculations at the “Ask Mr Electricity” web site, we estimate that it takes us around $0.06 to heat 5 gallons of water 40 degrees. This, plus the costs of water and sewer adds up to around $0.09 per load to hand wash dishes. (http://michaelbluejay.com/electricity/waterheaters-figures.html; January 31, 2016)

Following the process outlined below, we have found that we can meet the lower water consumption goal. We use dishpans to limit water use and rarely rinse dishes under a running faucet. Sometimes we use heated tap water, but an even better option is to use water from our rain barrels that is heated in our solar ovens.

Comparing Hand Washing vs the Dishwasher

Are the dishes washed in the dishwasher cleaner than those washed by hand, as the web site claims? Well, we don’t leave bits of food behind when washing dishes by hand. That is the reason why so many people rinse dishes before placing them in the dishwasher. We use vinegar in the rinse water to help get dishes squeaky clean. We use bleach if needed to sanitize the dishes, whereas it takes extra energy to run a dishwasher’s sanitize cycle.

Are there any hidden costs that the web site does not account for? Last I checked, cheap white vinegar, bleach and dish washing liquid cost much less than dishwasher detergent and rinse aides. The government website also fails to mention that a dishwasher is an expensive appliance to purchase! It could take decades to recoup the cost of a new dishwasher, and I doubt if a new model will last that long. Dishpans are cheap!

Will using the dishwasher save time? Not if we have to wait 2 hours to run the last load of the day before turning in! We can hand wash a large load of dishes in close to the time it takes to rinse and load them into a dishwasher, and have a nice chat with family or friends while doing it.

And so, contrary to the ENERGY STAR web site, we have concluded that washing dishes by hand is still much preferred to running the dishwasher, as long as a little attention is paid to the process. My simple cost comparison below assumes that one load of dishes is washed each day. However, when you are processing and preserving food, you may need to do several loads in a day – further adding to the savings. And even better savings can be had if you are able to use harvested rain water and heat that water in a solar oven!

Estimated Yearly Cost for Washing Dishes (7 Loads Per Week)

1. Dishwasher, Normal Cycle, Heated Rinse, No Dry Cycle
(Not including the cost of detergent, rinse aide, or the dishwasher for that matter!)
$55.00

2. Washing Dishes by Hand using Tap Water
(Not including the cost of dishwashing liquid and vinegar, dishpans or water heaters.)
$33.00

3. Washing Dishes by Hand using Rain Barrel Water and Solar Ovens
(Not including the cost of dishwashing liquid and vinegar, dishpans or solar ovens.)
$0.00

Instructions to Hand Wash Dishes using Tap Water

Materials
• 2 dishpans (15 quart capacity rectangular plastic pans)
• Dishcloth
• 2 tablespoons dish washing liquid
• ½ cup cheap white vinegar (bought by the gallon)
• 5 gallons comfortably hot water

Instructions
1. Fill one dishpan with 2 gallons of comfortably hot water and add the dish soap.
2. Fill the second dishpan with 3 gallons of comfortably hot water and add the vinegar.
3. Wash the dishes in the first dishpan; rinse in the second.
4. Use the dishwasher racks as a dish drainer and let dishes air dry.
5. When finished, hang the dishcloth to dry on the faucet or some other convenient place. Then rinse the dishpans and set them aside out of the sink to dry.

Instructions to Hand Wash Dishes using Rain Barrel Water and Solar Ovens

Materials
• 2 dishpans (15 quart capacity rectangular plastic pans)
• Dishcloth
• 2 tablespoons dish washing liquid
• ½ cup cheap white vinegar (bought by the gallon)
• 2 large pots to heat water
• 2 solar ovens

Instructions
1. Heat a large pan of rain water in each solar oven until the water is uncomfortably hot but not boiling. This can take some time. Be very careful when carrying the pots of heated water into the kitchen.
2. Fill one dishpan with the first pot of hot water. Add the dish soap and cool tap water as needed to make the water temperature comfortable.
3. Fill the second dishpan with the remaining hot water. Add the vinegar and cool tap water as needed to make the water temperature comfortable.
4. Wash the dishes in the first dishpan; rinse in the second. Wash the least dirty dishes first.
5. Use the dishwasher racks as a dish drainer and let dishes air dry.
6. When finished, hang the dishcloth to dry on the faucet or some other convenient place. Then rinse the dishpans and set them aside out of the sink to dry.

Below is pictured a load of hand washed dishes from breakfast and canning 10 pints of broth.