Hot Water? Ponder This...

[mrb627]

Which of these two scenarios is more energy efficient and why?

1. A standard top load washing machine in a household with a tankless water heater.
2. A front loading washing machine in a household with a 50 gallon water heater.

Now, supposing laundry is typically washed one day per week, does it cost more to heat the extra water needed in the top loader on demand than store 50 gallons of water at 140* all week long in a household with a FL machine that may then call on its own heater to further bring temperature up?

My logic seems to lean towards option 1 above as the more efficient scenario.

What do you think?

Malcolm

 

[golittlesport]

As far as looking only at the energy required to supply hot water for the wash segment of the cycle, I'd say scenario #1 would probably be more efficient.

But in the western U.S., where water is precious, scenario #2 would be more efficient as far as making efficient use of resources overall.

Of course, we haven't considered whether it's a gas or electric water heater.

 

[foraloysius]

I guess it also depends on the insulation of the tank water heater. And what about a solar water heater? That would certainly be more efficient in combination with a frontloader.

Considering that hot water is also used for other things I would choose option #2.

 

[sudsmaster]

Best to get a cold fill front loader with an internal water heater, if you can...

 

Judging from my own utility bills, the gas fired 50 gallon water heater doesn't use much energy in the summer, when compared with the usage in the winter when the gas is also used to heat the home. That's with the usual hot water consumption: showers, dishwasher, clothes washer, etc. The washer is a Neptune front loader, which isn't among the most water efficient these days, but which probably uses about half as much as a typical traditional top loader. Nearly all of the five to seven loads a week or warm or hot fill. Cold washing is very rare in this house.

 

Other than that, your questions amount to a false dichotomy. There are plenty of other choices, such as coupling a water efficient front loader with a tankless water heater, or choosing a front loader with cold fill and an internal water heater. Unless you're prepared to set up a lab to test your two options, and measure the exact energy usage, you'll never know the real answer. The best we can do is to make each part of the setup as energy efficient as possible.

 

 

 

[nmassman44]

I find that with my new LG washer that after 6 loads of laundry my water heater will kick on once and thats usually after the 3rd load. We have a gas 40 gallon Bradford-White with that new control system.It will only heat the water if the water temp at the bottom falls below a certain temp and I have it set at 140. I am thinking that I will drop the temp some to about 120 or so since the washer does heat its own water and maintains temps thru a wash cycle. If I had a tankless heater, I doubt that it would even kick on long enough to heat the water thats used. And my dishwasher heats water well so no issues with that either.
So I would say #2.

 

[mrb627]

But...

You are maintaining water in a tank that isn't being used for anything but showering.

Malcolm

 

[foraloysius]

If only for showering means one person in a household, the tankless could be interesting. If you have several people in one household and several bathrooms, I don't think a tankless would be sufficient.

 

[brisnat81]

Hi Malcolm,

What about a 100Gal Solar heated tank that only needs electric backup for 3-5 weeks per year coupled with a H+C fill FL machine? Essentially free hot water for 47 weeks a year as long as you don't use it all at once.

Then you're good for 10-15 loads before you run out of hot water.

With a TL machine you'd only get 3-4 loads.

Cheers

Nathan