If you’ve been following the kitchen rebuild, one of the things that I added was a Fisher-Paykel DishDrawer.  I’ll do a more thorough review later, but I’ve seen a number of comments about water and power usage, and various remarks about not wanting or using one because of boondocking habits.

Less Water Consumption

Contrary to a lot of those discussions, the water consumption in particular for the DishDrawer is the main reason I put one in.  At under 2 gallons per load, which holds quite a bit more than a sink piled full of dishes, it can get the dishes clean with a lot less water than I can washing by hand.

Very Low Power Consumption

Today, I decided to actually get some real-world numbers for power consumption as well.  Since I have the DishDrawer plugged into an outlet in the back of the cabinet (that I can reach!), I unplugged it and connected a Kill-A-Watt power meter.  I might get a little more sophisticated later and actually record the data, but for right now I just wanted to see total energy consumption.

The specifications list peak draw at 5.8A at 110-120V.  That means for the 2-hour cycle, it shouldn’t use more than 1.4kWh.  We expect that it will be a lot less than that.  If we take a look at the EnergyGuide label, it shows 141kWh per year, assuming 4 loads per week.  141kWh/(4 loads per week)/(365.25 days/year)*(7 days/week)=0.676kWh per load.

The first test is running the normal cycle, with Eco mode turned off.  It’s a 128-minute cycle, consisting of a 120F pre-wash, 130F main wash, a rinse, a 130F final rinse, and heated drying phase.

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During the drying cycle, I was surprised to see that power consumption held steady at only 10 watts.  If I wanted to be a little more precise, the chart would show 4Wh over the last 25 minutes, but that’s pretty negligible.

Cost per Load

Lets look at cost per load with a typical 12-volt DC lead acid battery system, and assume 80% overall efficiency.  That should take care of getting to 120-volt AC power at the dishwasher.  The EnergyGuide number would then equate to about 70Ah per load from the batteries.  In the real-world test (which doesn’t include the energy for the hot water), we used 0.45kWh, or about 47Ah from the battery bank.  If you’re paying for electricity, at the 2014 national average electricity price of $0.125/kWh, that’s just over a nickel per wash.

So far, I’ve been running the dishwasher once every two days or so.  That includes tossing in pots and pans, which fill it up fairly quickly.  But given these numbers, if I had 400W of solar on the roof, we’d be talking less than an hour per day to take care of the dishwasher.  Better still, since most of the energy is consumed at the beginning of the cycle, I could run the generator for a few minutes up front and have negligible impact on the batteries.

To each his or her own, but from now on I’ll be pushing a little button to get the dishes clean.  I’ll do another post later on with some more general comments about this machine, but if you can’t tell yet I’ll spell it out: I like it.