Today, I washed my hands at the kitchen sink while making lunch, and was unexpectedly chastised by my partner because she had just started the dishwasher. Apparently, she has recently come across something that has convinced her that running the hot water in your sink means the water that enters your dishwasher will be hotter (checks out), and thus the dishes will be cleaner. I tried searching startpage to see if this is real, but I couldn’t make it through even one llm-slop-ticle about it before my eyes rolled back into my head, so here I am asking y’all: chat, is this real? Doesn’t my dishwasher have a heating element? Is there any meaningful difference between heating the water with a hot water heater vs a dishwasher, other than I can’t use my sink while the dishwasher is filling and I have to pour a bunch of cool water down the drain?
No, buy a better dish washer. Mine heats the water after fill and before washing starts. The only reason to do this is if gas heat was cheaper than electric and the money saved is less than the hassle and the waste in doing it.
Let’s say you have a kitchen faucet with a high flow rate of 2 gallons per minute. And let’s imagine you need to run the sink for a long time, say a full minute. So perhaps you lose 2 gallons of cold water to flush the lines. (Assuming you don’t do anything with that water, which you can certainly choose to do so.) Some searching suggests the average cost of water in the US is $5-8 per 1000 gallons. Let’s make it a round $10 per 1000 gallons, or a penny per gallon.
So, even with generous assumptions, it costs you 2 cents in wasted cold water as you flush the lines every time you run the dishwasher. If you run the dishwasher every single day, that comes to $3.65 in wasted cold water. If the fancier dishwasher with the better heating element costs only a hundred dollars extra, it will still take 27 years for the extra cost to be paid back via saved water.
In practice, these numbers were chosen to be generous, and the payback period is likely over a century. Your dishwasher will not last 27 years, let alone a hundred. Plus the time value of money. In short, the fancier heating element will never come close to paying for itself. You’re paying for a convenience, not saving money.
If you’re trying to be savvy about saving water, use the un-hotted hot water supply line water to fill a pitcher. In case the water is too hot, let it cool. Use it to water your plants, fill your pets’ water bowl or dispenser, run it through a passive filler jug if you have concerns about water from your water heater, or add a little detergent while it’s still warm and go scrub your bathroom floors. Go, do it now, TheFartographer. You’ve been meaning to do it for days. Get off the Internet and go scrub your filthy bathroom floors right now. Why am I this way?