Dishwasher - Power Pig

2manytoyz · September 2009

I've been making a conscious effort lately to measure all the appliances in my home with a Kill-A-Watt meter (120VAC appliances), or with a clamp-on meter (240VAC hardwired appliances).

I recently upgraded my 19 year old 8 SEER A/C unit with a 15 SEER one (didn't want a Pureon system). My electric bill dropped by $50-$75/month.

When I moved into this house, I replaced all the appliances. The dishwasher was tested this weekend. It consumes a lot more power than I expected. Another thread mentioned the heating element does more than just dry the dishes. It runs almost constantly to keep the water HOT. My dishwasher doesn't have an option to turn this off completely. I can set it to air dry at the end, rather than using the heating element. Haven't tried that to see the power difference, but here are my numbers:

Frigidaire model FDB2415LFS0

Peak power observed.

Total power used for a standard (96 min) wash cycle.

My washing machine uses 250WH per cycle (worst case heavy load), the dishwasher 820WH. I was really surprised to see the numbers this high. The dishwasher might use less hot water than hand washing dishes, but it really doesn't matter since it continues to heat the water anyway.

I'm slowly learning the Energy Star label doesn't mean much. Next time I buy one, I'll see if I can find one that gives the user the option to turn off the heating element entirely. For now, I'll be using the dishwasher less, and not at all from alt-power.

Cariboocoot · September 2009

Re: Dishwasher - Power Pig

Energy Star rating is relative - it means that unit is low on power consumption compared to comparable models. Doesn't that just make you shiver?

Dishwashers do indeed use a calrod to keep the water temperature high while washing - for sanitary reasons. Really all they do to wash is spray water around - unlike sink washing where you can scrub and be sure soap gets on everything. The high temperature water tries to make up for this. That is why disconnecting it is a bad idea: ordinary tap hot water is usually 140 F - too low for sanitation - and it won't stay that hot while washing.

The best you can do is load it properly and go for "regular wash" instead of longer cycles like "pots and pans" or "heavy load".

BTW some clothes washers these days have "sanitize" cycles or "steam" which, of course, use built-in heating elements to really waste electricity. Er, I mean help clean the clothes.

Electricity is a lousy way to heat things.

2manytoyz · September 2009

Re: Dishwasher - Power Pig

The sad part is this was a regular wash. It does have a sanitizing setting as well (hate to test that one!).

The Electrosol tabs I use have bleach in them as well. Even with just hot tap water, still more effective killing germs than hand washing dishes in warm tap water and dish soap.

This was a worthwhile test. I made the mistake of watching a TV show saying how energy efficient Energy Star dishwasher are, and how they use less hot water. But they neglected to mention how much power they consume to use less hot water.

BB. · September 2009

Re: Dishwasher - Power Pig

Every time I looked for a dishwasher--they were always on the scale of a full size fridge worth of power usage (~1kW per wash per day).

You have just confirmed it with real world measurements.

And, for those of us that try to keep our water heater costs down, we keep the water around 120F at the faucet--So it pretty much guarantees that the dishwasher will need to heat the water with more electricity.

I have not cranked up our dishwasher in over 4 years--and just hand wash instead. (over $0.10-$0.20 worth of electric power per load :roll: )

-Bill

Brock · September 2009

Re: Dishwasher - Power Pig

We also have Frigidaire's, yes two, with lots of home cooking and 4 kids... Anyway I played around with this a lot when we first got them. The "regular" wash heats up to some point, I am assuming 140F. Since our water was heated geo-thermally I bumped up our hot water heater to 150F and sure enough I had two loads come in under 250WH each. But leaving our water set about 120F will typically get us about 750WH per load. If you turn "high temp" ( iirc 150F) on it came in about 1200WH and of course my wife favorite sanitize (160F for one cycle) was north of 1500WH.

I think it depends on how hot your "hot" water is. I found by running the kitchen sink until the water was hot first saved us about 250WH. Now I try to get her to either run them both at once or wait until the geo has the hot water as hot as it will get before running them.

Cariboocoot · September 2009

Re: Dishwasher - Power Pig

Meanwhile detergent companies keep pushing their cold water formulas. Ironic, isn't it?
We wash with cold water and regular detergent and it comes out fine. Colours don't fade so much either.

BillF · September 2009

Re: Dishwasher - Power Pig

About 10 years ago I disconnected the heating element under the dishwasher. Hot water heater is set to 120F. Hasn't killed us yet.....Possibly the dog or the bleach in the dishwasher soap are keeping us alive. Your choice

mike95490 · September 2009

Re: Dishwasher - Power Pig

BillF wrote: »

About 10 years ago I disconnected the heating element under the dishwasher. Hot water heater is set to 120F. Hasn't killed us yet.....Possibly the dog or the bleach in the dishwasher soap are keeping us alive. Your choice

Do you have one of these dishwashers, very low water usage, but the rinse is often inadequate.

Dave Angelini · September 2009

Re: Dishwasher - Power Pig

Cariboocoot wrote: »

Electricity is a lousy way to heat things.

Very true especially when you can heat water with solar so easily. I have to cover half of my panels during the summer to keep the water below 160F. Thankfully the two cats never get in the house where the dishwasher is.

2manytoyz · September 2009

Re: Dishwasher - Power Pig

Brock wrote: »

I think it depends on how hot your "hot" water is. I found by running the kitchen sink until the water was hot first saved us about 250WH. Now I try to get her to either run them both at once or wait until the geo has the hot water as hot as it will get before running them.

Great number comparison, thank you!

I have our thermostat on the electric WH set at about 140. The dishwasher is next to the kitchen sink, and I always run the faucet until the water is up to temp before kicking on the dishwasher. The data posted was best case scenario for my setup. I could understand the figures if the water was cold going in.

I might try the air dry feature, and see if that significantly drops the overall WH.

mshen11 · September 2009

Re: Dishwasher - Power Pig

[I have not cranked up our dishwasher in over 4 years--and just hand wash instead. (over $0.10-$0.20 worth of electric power per load )]

question on that - we did not use our dishwasher for 2 years and one day when we wanted to it died. we were told if we didnt run it once a month, that is exactly what will happen.

i wasnt told the reasoning why. does anyone know? also how do you prevent your dishwasher from dying of disuse?

now i have a dead dishwasher - since we never use it, i didnt replace it. also for some reason our daughter likes to play in it (yes its clean)

[I think it depends on how hot your "hot" water is. I found by running the kitchen sink until the water was hot first saved us about 250WH. Now I try to get her to either run them both at once or wait until the geo has the hot water as hot as it will get before running them. ]

but then you waste water. but then water is probably cheaper.

Cariboocoot · September 2009

Re: Dishwasher - Power Pig

Dishwashers are full of parts. Some of them are rubber and meant to keep water from leaking out and on to the floor or into the pump motor. Without water, they dry out. They then leak or break or both the minute you try to use them again. So bits of rubber pump impeller can flake off and jam the pump or water can leak past the pump seal and soak the motor, or past other seals and get into wiring.

Yup; use 'em once and let 'em sit for a couple of years and you're bound to have trouble. If they're never used, they last a bit longer but the stuff still dries out. It just happens faster after they've been exposed to water and detergent and gunk from dirty dishes.

mike95490 · September 2009

Re: Dishwasher - Power Pig

Belts and bearings. When not used, they stiffen up. I was able to kill power and crank the pump over by hand, 10 degrees at a time, after about 2 hours laying on the floor with my arm up the dishwashers guts, I got the pump loose enough to have the belt spin it. It had a squeal of about 130db, we'd load the beast, start the flow, and dash out of the house to a movie for 2 hours. The bearings never were right after they seized. Eventially bought a new dishwasher that was nearly silent, use it about 1x a week.

Dishwasher soap has lube agent in it too, like antifreeze has for your water pump in a car.

mshen11 · September 2009

Re: Dishwasher - Power Pig

so once you use a dishwasher, you better use it. no way around the drying and eventually cracking of rubber parts?

if you never use it... then what purpose is a dishwasher? other than a toy for your kid.

Cariboocoot · September 2009

Re: Dishwasher - Power Pig

mshen11 wrote: »

so once you use a dishwasher, you better use it. no way around the drying and eventually cracking of rubber parts?

if you never use it... then what purpose is a dishwasher? other than a toy for your kid.

Well you could use it to store dishes in.

But yes; leave it and lose it. You could run it once a month to keep it up I suppose. Adds to the re-sale value of the house (if it works). Nice, clean (never-been-used) dishwasher looks good to prospective buyers.

mike95490 · September 2009

Re: Dishwasher - Power Pig

Cariboocoot wrote: »

Well you could use it to store dishes in.

After the '71 Sylmar earthquake in Calif, the only dishes my grandmother had, were the ones in the dishwasher. Everything else was gone. She was 5 miles of ground zero of a 6.6 shaker.

Dishwasher - Power Pig

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