Dishwasher Power Usage

[DADoES]

 
I ran an updated test with my Kill-a-Watt meter on power usage for a load of dishes.

Normal cycle, which heats the wash to 140°F, final rinse to 150°F.  Initial estimated time 115 mins, extended as needed to reach the target temperatures.  I didn't clock what was the full time.

Water heater is normally set at 104°F.  I raised it to 123°F an hour before starting the dishwasher for washing a load of bedding, and hand-washed an item at the sink, so the supply line was fully purged to a hot flow at that point.  The water heater reverted back to 104°F by the time the dishwasher started so the supply line had only residual heat.

Pump in drain mode = 30 to 40 watts

Pump in recirculation mode = 120 to 125 watts

Pump + heating element = 650 watts

Drying blower = 7 watts

Total power usage = 0.48 kWh

Cost at my electric rate per last bill = $0.0527

 

[Chetlaham]

Mad respect! Thank you for taking the time to obtain these numbers.

 

[oldschool88]

Nice data! While we were without utility power for 5 days following hurricane Isiaias back in August, I ran our Bosch 300 (model # SHEM63W55N) on our Honda EU3000is inverter generator. The door sticker says 1.2KW, or 12A. No issue for the Honda while also powering a few lights, FIOS multiplexor for TV and Internet, and our main fridge.

Now I'm wishing I'd run it through my Kill-A-Watt as you did. Next hurricane...

While running on 3KW of inverter generator power, I did find that my garage fridge was a real power pig and we replaced it. 780W running, and enough surge during compressor start that the whole house lighting browned-out every time the thing cycled. Not that the compressor shut off very often in high garage temps. 1991 GE top freezer, no compressor start capacitor by design. I debated adding a start capacitor kit, but the running wattage was a deal breaker. Frigidaire 2004 model we bought used only shows 102W running, and it maintains temp more precisely (narrower hysteresis) than the old GE.

 

[frigilux]

Thanks for taking the time and effort, Glenn. It’s always Interesting to find out exactly how much power an appliance is using at various stages of the cycle.

 

[johnb300m]

104?

Not to be a nudge, but water heater at 104 degreees is in the sweet spot for Legionnaires bacteria.
Jussayin.

https://www.cdc.gov/legionella/wmp/overview/growth-and-spread.html

 

[DADoES]

 
My water heater is a tankless unit.  It heats only when water flows through it.  The only way to keep it continuously hot is run hot water 24/7, which defeats the purpose. 

 

[luxflairguy]

What's the fuse size for these? Very professional install!!

 

[DADoES]

 
Water heater is two 60s at top left.  50 beneath is range.  60 and 30 at top right is HVAC air handler.  30 beneath is dryer.

Pic 2, eight 40s on the water heater subpanel.

 

[luxflairguy]

WOW! Thanks!

 

[ozzie908]

Daft question but

Is this tankless water heater able to provide the whole house? Its interesting as we have a gas version that heats as and when its needed but as our appliances use only cold water its not needed for them.

Austin

 

[combo52]

DW Power Consumption

Hi Glen I love this post, it is always fun to see accurate numbers on power and water consumption etc on home appliances.

 

I assume that these figures are for one of your F&P Dish-Drawers.

 

I have often wondered on my WP DWs how much the power use is affected by the amount of dishes are in it since the heater must heat all the dishes in addition to the water. It would be interesting for you to run your DW empty to see how much difference it makes.

 

John L.

 

[DADoES]

 
Normal Eco

125°F wash and final rinse.

Purged the supply to warm-feeling on 104°F setpoint.

4 water changes -- prewash (or rinse if no detergent), wash, rinse, rinse.

88 mins initial time.

86 mins clocked time.  Dry period began at 22 mins.

0.33 kWh power usage.

$0.036 cost.

 

[wayupnorth]

No matter what your KWH is, it is always cheaper and more efficient to use a dishwasher 1X day, no matter what kind it is, than running hot water in a sink 3X a day to do each meals dishes.

 

[DADoES]

 
Austin,

It's the only water heater in the house.  I've not yet in 15.5+ years had an incident of insufficient heated water.  I know electric tankless is not usually chosen, in favor of gas.  Reasons the builder opted for electric presumably are 1) there is no natural gas service in this little neighborhood outside town and 2) both bathrooms have whirlpool tubs so sufficient capacity is needed to handle them.  I've never had a need to fill both at the same time but filling one would challenge a typical-size tank heater.

 

[launderess]

"dishwasher for washing a load of bedding"

Bedding? Or maybe I shouldn't ask.....

 

[tolivac]

Use the right tool for the right job?

 

[Marky_Mark]

Great information, Glenn.  I like experiments like this!  Thanks for posting.

 

If you connected your dishwasher to cold water, my understanding is that in your situation it would cost you less.  The dishwasher would use more energy but your tankless electric water heater would use nothing.  Overall you would save energy.  Different dishwashers (and cycles) respond differently to this and performance may increase, decrease or stay the same.  Some add more time.  It would be interesting if you tried running another load with the water heater turned off and no hot water remaining in the pipes.  If you do, please post the results!

 

It sounds like your electricity rate must be fractionally under $0.11/kWh.  I wish it were that cheap here in SoCal!  We pay less than $0.04/kWh for gas but electric rates are tired and I pay between $0.22 and and whopping $0.35/kWh!  I have a gas water heater and a hot water circulation pump, so hot water is immediately available everywhere including at the dishwasher for every fill.  So it makes a lot of sense to have my dishwasher hooked up to hot.  It is cheaper for me but does use more energy. 

 

[ozzie908]

Dadoes ....

I am suitably impressed that your heater is able to supply all the needs it goes to prove there is no need for a tank of hot water to sit there waiting to be used.

Does the heater need any maintenance ?

Am curious as never seen a house version it reminds me of our electric showers they are 8.kw and heat straight away so no waiting etc.

Austin

 

[DADoES]

 
Maintenance:  Occasional descaling (with vinegar).  Haven't done it in ~2 yrs.

Today's power test:

Delicate cycle.  120°F wash, 130°F rinse.

86 mins initial time, I missed noting the actual.

Dry period started @ 25 mins.

Did not purge the supply line so essentially ran on tap-cold.

0.38 kWh usage.