I'm just about to purchase a new dishwasher. Which is best for energy efficiency, one that heats up the water or one that uses already heated water? I have SHW and PVs on the 60c tariff. 
Water Heating For Dishwashers
(98 posts) (20 voices)-
Bushwalker
MemberEnergyrating website should help you:
Posted Friday 7 Aug 2015 @ 12:55:46 pm from IP # -
johnmath
MemberDishwashers should normally be connected to cold water. Here's why:
1. Dishwashers on use a couple of litres of water at a time. If plumbed to hot water, the dishwasher will fill with cold water from the pipes and the hot water entering the pipes is just wasted heating the pipes, which will be cold again by the time the dishwasher needs more water.
2. Proteins (e.g. egg) don't clean well in hot water. Starting with cold water and heating it during the wash works better.
3. There are several cold water rinses during the washing cycle where heating the water serves no purpose. If hot water is used unnecessarily overall energy consumption will be greater.
4. Dishwashers dry dishes by heating the dishes with a hot water rinse, but the steam given off has to be condensed somewhere other than back on the dishes. Dishwashers fill with cold water at the end of the cycle for this purpose. It the final fill is with hot water, the dishes won't dry properly.
Posted Friday 7 Aug 2015 @ 9:31:10 pm from IP # -
Oilburner
MemberIt seems very hypocritical to me that people ask about efficiency/ power/ water/ whatever consumption in the case of dishwashers.
If you really are so concerned about saving energy/ water/ the environment etc, why the hell are people even talking about Dishwashers here???
We still do the dishes at home by hand and manage to survive without feeling our lives are overburdened or we are suffering like slaves.
If people really are committed to the things I see being paid lip service to here, then I would Imagine a dishwasher would be the last thing they would be worried about.Talking about dishwashers on a forum like this is the same hypocrisy tome as the people that I see at the Gym driving round and round to get the closest carpark to the door and then go downstairs and are hoeing into a large fast food meal with the dessert afterwards.
Posted Sunday 9 Aug 2015 @ 9:24:43 am from IP # -
Annette
MemberHi Oilburner
Quite the opposite!
In the past, I also struggled with the idea that dishwashers can contribute to sustainability - certainly in terms of water saving and possibly in terms of energy too.
I flat out just didn't believe it and (just privately) I tended to be a tad judgemental - until I read some articles that showed that using a dishwasher uses less water than doing the dishes by hand.
(well, I guess that if you just use and reuse one bowl and wipe it out rather than washing, Iike when camping, then you may use less - but I am referring to 'normal' family use).
Real greenies use dishwashers too!
Posted Sunday 9 Aug 2015 @ 10:00:18 am from IP # -
Benny
MemberRight on Annette. A typical dishwasher uses 10-12L per load and less than 1 unit of electricity. As you say - as long as it is filled up - perhaps with 2-3 days dishes - then this is very economical/efficient.
As for comments from "oilburner" abut hypocrisy ......
Posted Sunday 9 Aug 2015 @ 12:34:16 pm from IP # -
Sunshine
MemberI have SHWS and PV panels for 7 years with an energy monitoring system which measures power usage per appliance.
Using hot water connection dishwasher uses 400wH, rather than 1.7kWh as specified in handbook using cold connection.
Have never had any issues with cleaning dishes with egg etc, nor with dishes being wet at end of cycle.
Just purchase a dishwasher which takes a hot connection (most don't), and ensure you have a tempering valve which drops temperature to 60 degrees.
If you want to save further money, use vinegar in lieu of liquid Finish, and you will save money on chemical costs, and repair bills, as vinegar keeps the internals of machine clean.Posted Monday 10 Aug 2015 @ 3:02:16 am from IP # -
dlvb19
MemberMy dishwasher uses 1.5 kWh per cycle - I use the pots and pans though and load it HEAVILY!!
Average sink in 20 litres - assume fill 3/4 with 50 degree water - assume 2 sinks full and no rinsing. Assume outside water 10 degrees (accurate for my location). This are super conservative assumptions for the amount of dishes I'm considering.
Specific heat of water is 4.2 J/g.K.
4.2 * 30,000 grams of water * 40 degrees kelvin = 5,040,000 Joules or 5.04 MegaJoules.
Cos I'm a nerd I know 3.6MJ = 1kWh so 5.04MJ = 1.4 kWh.So its pretty close but as I mentioned they are super conservative assumptions - energy use will likely be higher. Also dishwasher uses about 12 litres - compared to 30+ litres....but I'm on tank water so I don't really care (so long as it doesnt run out)
Posted Monday 10 Aug 2015 @ 4:35:31 am from IP # -
johnmath
MemberOilburner said:
It seems very hypocritical to me that people ask about efficiency/ power/ water/ whatever consumption in the case of dishwashers.If you really are so concerned about saving energy/ water/ the environment etc, why the hell are people even talking about Dishwashers here???
Because study after study has shown that using a dishwasher correctly uses LESS water and LESS energy than doing dishes in the sink, that's why!
Posted Monday 10 Aug 2015 @ 10:05:47 am from IP # -
Oilburner
Memberjohnmath said:
Because study after study has shown that using a dishwasher correctly uses LESS water and LESS energy than doing dishes in the sink, that's why!First thing is what is " Correctly" and how many people did all these studys find actually do that?
Secondly, Who commissioned the studys?
Wait, don't tell me, it was the manufacturers of the dishwashers or someone they paid to do the studys right?I can show " studys" that show Smoking does you no harm, HV power lines are safe and asbestos in not Dangerous. There was plenty of those "studys" done too.
Is there a study that shows a dishwasher going through a normal cycle with a water and power meter connected?
Posted Monday 10 Aug 2015 @ 10:30:31 am from IP # -
cava
MemberAs someone who has overseen the Energy and Water Label testing for more dishwashers than I can count from many manufacturers, I can advise that very few will actually perform satisfactorily in a domestic environment with a 'full load'. We constantly had to juggle the eprom to get a satisfactory setting.
The heating of the water in the cycle chosen is not the main issue. The quantity of water used is the problem.
In my own home, and for the style of cooking we eat, typically once every 7-10 days my wife has to rewash the complete load - this despite using the longest most severe cycle the dishwasher has. Also being on septic has it's shortcomings, with us being forced into using a more ecological detergent.
Posted Monday 10 Aug 2015 @ 12:53:43 pm from IP # -
johnmath
MemberOilburner said: Who commissioned the studys?
Wait, don't tell me, it was the manufacturers of the dishwashers or someone they paid to do the studys right?Nope. Here's one from Bonn University Germany (not a manufacturer is sight):
The Bonn University study shows that the dishwasher uses only half the energy and one-sixth of the water, and less detergent. Even the most sparing and careful washers could not beat the modern dishwasher. The study also rated the cleanliness achieved, again in favor of the washing machine.
http://www.landtechnik.uni-bonn.de/research/appliance-technology
This is from the US:
Dishwashing vs. Hand-Washing Which method uses less energy? Studies are showing more and more that, when used to maximize energy-saving features, modern dishwashers can outperform all but the most frugal hand washers.
http://smarterhouse.org/dishwashing/energy-saving-tips#sthash.n32JsYzp.dpuf
Posted Monday 10 Aug 2015 @ 2:20:35 pm from IP # -
tom rickard
MemberAs I don't live in a cave, I have children, and buy food from the supermarket, i'm not in a position to criticize people for unnecessary energy usage.
Having said that, our dishwasher is our biggest individual energy user, so I think it's a good idea to get one that is as energy efficient as possible.
As for the energy site, It must use the most economical setting available on the dishwasher, I have a Bosch, and it uses 1.4kwh on the "normal" setting. I see the energy site has it listed at less than 1kwh. If I use the "eco" setting, the clean isn't good enough.
Posted Monday 10 Aug 2015 @ 11:02:44 pm from IP # -
Benny
MemberOn my Bosch dishwasher all the eco setting does is stop the final drying cycle - it doesn't affect the washing cycle. We just open the door when it finishes and let the dishes air dry.
Interesting Tom that your dishwasher is the highest energy user - even less than your fridge(s) ?
Posted Tuesday 11 Aug 2015 @ 12:26:05 am from IP # -
Bushwalker
Member+1 for Bosch. Effective and economical, even using septic friendly powders.
Posted Tuesday 11 Aug 2015 @ 4:05:24 am from IP # -
Oilburner
Membercava said:
As someone who has overseen the Energy and Water Label testing for more dishwashers than I can count from many manufacturers, I can advise that very few will actually perform satisfactorily in a domestic environment with a 'full load'.The heating of the water in the cycle chosen is not the main issue. The quantity of water used is the problem.
Do you mean the qty of water per load is the issue or the fact that a re wash has to be done every so often increasing the water use?
Did you find the water and electrical usage quotes to be accurate?
Posted Tuesday 11 Aug 2015 @ 10:24:49 am from IP # -
cava
MemberQuantity of water in litres per load is the biggest problem, and there is allowed be be a tolerance in any of the figures.
I am not sure what the +/- tolerance is at the moment, but from memory 10% on water consumption vaguely resonates with me.
Posted Tuesday 11 Aug 2015 @ 10:58:13 am from IP # -
GJOESQ
MemberThanx to all of you for your contributions to this topic.
To reassure Oilburner, I always wash by hand because I'm frugal and haven't been impressed with the results of dishwashers. The reason I'm buying one is that the folks living in my home asked for one. I guess my main question was if a cold water or hot water connection is preferred. I think the hot water one is best in may case. Thanx for the vinegar hint, Sunshine. I use vinegar for many cleaning jobs. It's great and inexpensive.
For the record, I bought a Dishlex Dishlex DSF6105W, one of the best performers and cheapest in Choice's tests. I got it for just $489! Some of those damn things can cost over $3,500, like the Miele G5935 SCi XXL, which had a washing efficiency of only 72% compared to the Dishlex's 81% @ one seventh of the price!!!
Posted Tuesday 11 Aug 2015 @ 11:59:35 am from IP # -
cava
MemberChoice do their testing with a maximum of five (5) place settings regardless of what the manufacturers instruction manual states.
This has caused much consternation when a manufacturer is doing testing for WELS/EER labeling as it is incompatible with Choice's criteria.
Posted Tuesday 11 Aug 2015 @ 12:34:06 pm from IP # -
tom rickard
MemberBenny said:
On my Bosch dishwasher all the eco setting does is stop the final drying cycle - it doesn't affect the washing cycle. We just open the door when it finishes and let the dishes air dry.Interesting Tom that your dishwasher is the highest energy user - even less than your fridge(s) ?
Yes, my Electrolux fridge averages out at 1.3kwh/day, we use LPG hot water and cooker. If I run both my evaporative air conditioners flat out they would use more, but I haven't had to do that so far. Things will change when we go to refrigerated air conditioning.
Posted Tuesday 11 Aug 2015 @ 12:35:13 pm from IP # -
hamish05
MemberI converted my dish washer to hot water some years ago, after checking with the manufacture that it wouldn't be harmful.
I have Solar hot water and it just didn't make sense to me to be paying to electrically heat the wash water.
Here are the results for my Dishwasher using both COLD and HOT WATER.
COLD Eco Wash .610 kWh/wash. HOT Eco Wash .275 kWh/wash. (11 min. quicker)
The Dishwasher is an Electrolux (Dishlex) Mod DX403SB.
It cost me $13.25 for some fittings, to convert from cold to hot. The "cook" cannot detect any difference in the wash quality.
Posted Tuesday 11 Aug 2015 @ 12:52:48 pm from IP # -
Bushwalker
Membercava said:
Choice do their testing with a maximum of five (5) place settings regardless of what the manufacturers instruction manual states.This has caused much consternation when a manufacturer is doing testing for WELS/EER labeling as it is incompatible with Choice's criteria.
Well, that's just stupid. Buy a 10 place dishwasher to wash 5 places?
If you sort the energyrating dishwasher list by energy use, the top dishwasher (V-ZUG) 14 place, uses 111 kWh and is 6 stars. There is a Bosch 6 place washer a few (6) places down that uses 135kWh but is rated just 3 stars. The worst is a NEFF that is 13 place and uses 405kWh but gets 2 stars, only one less than the Bosch.
If you divide the energy use by the place settings, V-ZUG is 7.92; Bosch 22.5; NEFF 31.1 So the issue is really, are you filling your dishwasher or are you loading it lightly and running it every day?
If Choice really wants to create their own standard, they should back it up by doing back to back testing against the WELS/EER standards.
Plenty of people only run their dishwasher when it's crammed full. In that case, neither Choice nor WELS/EER are relevant. It comes down to the total energy and water use and the number of dishwasher runs per week.
If people are daily running their dishwasher partly full, they are using much more resources than the group of people who fill their dishwashers regardless of the standards based efficiency.
Posted Tuesday 11 Aug 2015 @ 10:06:12 pm from IP # -
Bushwalker
MemberDishwashers don't use detergent, they basically have an alkaline powder that burns the residue off the plates. That's why they can stuff up your septic.
Posted Wednesday 12 Aug 2015 @ 2:05:00 am from IP #
