Dishwasher Efficiency - Water Temperature Edition

My sister recently bought a brand new (gorgeous) house.  With the brand new house came brand new (shiny) appliances.  The dishwasher installer told her that she should run the tap water in the sink until it’s hot before starting the dishwasher.  Huh?!?!  We’d never heard that before and it was news to everyone I’ve asked about it since.  To me, it seems a bit wasteful and unnecessary since there are heating coils in the base of the dishwasher. 

Well, I did a little research on the topic and it turns out it’s a pretty common recommendation amongst appliance experts and manufacturers.  Here’s what I learned: 

• Water temperature is one factor (along with how you load it & what detergent you use) that affects your dishwasher’s effectiveness.  The target temperature varies by manufacturer, but it’s around 140°F.  However, the maximum recommended temperature for your home’s water heater is 120°F (much higher than that and you run the risk of scalding your skin).  So even if you run the faucet for a few minutes before you start the dishwasher, it’ll still need some extra heat from the machine to reach that 140°F mark.
• The dishwasher will extend a cycle in order to get to the appropriate temperature. Further, the heating coils in the base of the dishwasher are designed more to maintain the temperature of the water, rather than heat it up.  So if the water entering the machine is already hot, the dishwasher will not “waste” time waiting for the water to heat up, in turn maximizing the cycle time.
• Some newer models have a heat booster that heats the water before it enters the machine. If you’re in the market for a new machine, these are touted to save you tens of dollars a year on your energy bill.

Bottom line:
Running the tap in the sink by the dishwasher before running a load will get the water to the optimal temperature quicker.  According to my research, this could shorten the length of your dishwasher’s cycle.  

The proponents of the pre-cycle faucet run suggest that if you’re concerned about efficiency and conserving water/energy, you could capture the water in a container that you can use for watering plants or another purpose.

Final thoughts:

As I researched this I realized that, more often than not, I’m running warm water as I’m loading the dishwasher anyway.  So if you’re on Team Rinse Before Loading or if you have opted to own and use items that must be hand washed (eek!), you’re probably getting a head start already.

Even with all of this information, I’m not sure I’ll be changing my practices.  Maybe some scientific studies need to be completed in the Order Up test kitchens.  Maybe I could find a way to get Marshall Dillon involved?  But I’m not sure this is the answer.

What about you?  Is this information new to you?  Will it change your dishwasher practices?  Or do you already wash by hand?