Episode 1: Test Details

We hand washed dishes three different ways for our test, and used three different washing machines as well. If you’re beguiled by details, then be prepared to be dazzled!

General

Before we ran our tests, we “pre-charged” our water lines with hot water. This means that our sinks and dishwashers got the full hot water temperature right away.

The hot water right at the wall was set to 120 degrees.

To calculate the energy that went into heating the water used, we took the total gallons of hot water used and figured out how much energy it would take to get that amount of water from an average cold water temperature back up to our 120 degree mark.

For each cleaning pass, we used the same set of 52 dishes, bowls, glasses, and silverware, which we dirtied up with tomato sauce. We used tomato sauce because it is nice and bright red, which makes it easy to see when things (especially white plates) are clean.

Hand Washing

We used a two-sink setup in our tests. Each sink held around 8 gallons.

Whenever hot water was called for in the hand washing tests, we used hot-as-we-could-stand water (which turned out to be about 107 degrees). To get this temperature, we mixed down our 120 degree hot water with cold water. To figure out how much energy we used, we only measured the amount of water that went through the hot water side.

The faucet on our sink could put out a lot of water, but we used a flow of about 2 gallons per minute (GPM) for our experiments. Depending on when your kitchen faucet was made, and how much its designers had efficiency in mind, your faucet may use less than our 2 GPM to as much as 7 GPM. If you have a faucet that puts out a lot of water, then a 15 minute dishwashing sessions could have you consuming over 100 gallons of water if you leave the water running the entire time. In contrast, filling our sinks half way used a total of 8 gallons. So even if the water had gotten bad enough that we had to refill both sinks in our two-sink setup, it still would have only used 16 gallons. And keep in mind that half of that was cold water.

We pre-scraped dishes regardless of which kind of test they were heading to.

Constant Water Method

For this test, we turned on the the hot-as-we-could-stand-it water when we were ready to start washing, and turned it off when we finished our last dish.

We applied dishwashing liquid directly to the sponge whenever we needed some.

Rinse-Only Method

For the rinse-only test, we filled one side of our sink half way up with hot water, added dishwashing liquid, and started scrubbing.

We put as many dishes as would fit into the wash side to let them soak while we were cleaning. Whenever we had enough room, we added more.

Whenever we needed to rinse something, we would turn on our water to about 2 gallons per minute at the preset temperature of about 107 degrees, and then turn it off when the item seemed rinsed. We rinsed most things individually, but did rinse some silverware in batches.

We didn’t end up having to refill our sink.

Two-Sink Method

For our two-sink approach, we filled one side half way with hot-as-we-could-stand-it water (adding dishwashing liquid), and the other side half way with cold water.

We soaked and washed just like with the rinse-only approach, and then briefly dunked each item in the cold water side for a rinse (occasionally doing more than one piece of silverware at a time).

We didn’t end up having to refill either of our sinks.

Machine Washing

For the machine washing tests, we used three different dishwashing machines:

A machine that we bought used that was new a little over 10 years ago. It turns out that when this one was new, it was pretty inefficient compared to other new machines at the time.
A cheap, low efficiency dishwasher that we bought new at an appliance store (where we looked around until we found the least efficient machine they had).
A decidedly not-cheap, high efficiency dishwasher that we custom-ordered after finding the most efficient non-compact dishwashers listed on Energy Star’s web site (http://www.energystar.gov/index.cfm?fuseaction=dishwash.display_products_html).

On all three dishwashers, we used the “Normal” cleaning mode. They all had something like a “light”, “short”, or “econo” mode, which we didn’t use because we wanted to see how they would perform the way that most people would use them. If your machine has a setting like this, give it a try. It probably won’t work on everything, but you might find that it works just fine on certain kinds of dirty dishes (let us know what you find!).

We turned off any “heat dry” or “sanitize” options for our tests.

Welcome.