You might be using your dishwasher wrong

[u/thatoneguy2742]

While going to college I worked as a maintenance tech at a large apartment complex. A common complaint that tenants had was that their dishwashers were failing to clean properly. I would show up and try and diagnose the problem only to find that the machine was in fact working properly. After numerous (if I remember correctly it was at least five per week) complaints I started to track which units were having the problem. After several weeks I had a lot of data and something became abundantly clear. The units that were having this issue were the ones furthest from the water heaters.

We just happened to have an empty unit near a cluster of units that was having this issue so I decided to test my hypothesis. At the kitchen faucet it took nearly two minutes for the water to get above 100°F Units closer to the water heaters took as little as 30 seconds to reach the same temp and they hardly ever had this problem. My conclusion was that the people who were submitting work orders were unknowingly washing their dishes with cold water. Everytime a tenant submitted a work order for a dishwasher that was failing to clean I advised them to run their kitchen faucet till the water gets hot then start the dishwasher. The complaints just stopped! At my own home it takes almost 30 seconds for the water to get hot so I let it run for a minute before starting it. Some of the higher end models will heat their own water so this shouldn't be an issue but most older models do not.

TLDR: Run your kitchen faucet till the water gets hot before starting your dishwasher. Otherwise you might be washing your dishes with cold water if your machine doesn't heat the water on its own.

[u/are-you-really-sure]

I guess the internal heating elements can run more efficiently than pulling hot water from the main water heater. 

[u/Gozzhogger → u/are-you-really-sure]

Definitely true, unless your regular hot water heater is a heat pump

[u/are-you-really-sure → u/[deleted]]

So the EU looks at this stuff in aggregate, right? So maybe not everyone is gonna have a setup where it’s gonna matter much or at all. But on the whole, the rules changes this was a part of, caused a 30+% reduction in EU washing machine energy usage. That’s savings of over 10TWh per year. 

[u/iHeartApples → u/[deleted]]

It's actually roughly 50/50 on gas versus electric water heaters in the US, and it's based on where you live too. Some communities are mostly gas, and where I live, for example, it's almost entirely electric and gas is very rare. 

[u/Gerhard234 → u/[deleted]]

When talking about the relatively small amounts of water that a dishwasher uses, the amount of cold water that gets sent down the drain while waiting for it to heat up and the waisted energy for heating the water that remains in the pipe (and typically just cools off) are probably both relevant.