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?
They both have electric heating elements so identical efficiency. The advantage is that priming hot water means it’s hotter for longer and reaches a higher peak temperature in the dishwasher, which means more effective cleaning.
Not every home heats their water with electric resistance heating. My previous place used natural gas for hot water, and my current home has a heat pump water heater, which has an effective efficiency much greater than a normal electric water heater.
The heating element in the dishwasher at best maintains the water at a warm temperature. It will not instantly heat the water up for the very short first cycle of prewashing, just like if you suddenly put cold water into a water heater it wouldn’t be suddenly hot. It takes a lot of energy/time to warm water up.
My statement is taken directly from TCs video where he graphed the temps for primed vs unprimed washing. Priming the water leads to hotter (higher peak) and more area under the curve. Not priming leads to lower peak temps, but it’s certainly warmer than at best warm. The element will heat your water up even hotter than it comes out of the primed line, assuming you primed it.
When I open my dishwasher it is absolutely steaming and the dishes are too hot to handle. This temperature is above the setting on the hot water heater, ergo this extra heat can only have come from the heating element. It provides significant extra heat.
You are correct that it will take significantly longer than the prewash cycle’s duration and is not something to be relied on if you want optimal washing.