Another hot water on demand thread

[Dexter]

I am really struggling with the idea of getting a conventional hot water tank OR hot water on demand (new construction)...
I don't know who to believe- plumbers that sell HWOD, plumbers that don't(and don't like the idea), or everyone that swares by them because Europe has had them for ages(even if they themselves have never used it), or people from warm climates that don't need to heat the water as much as my glacier water will need, etc etc... It's not easy!

I've decided if I get on demand, to go with a propane model, because it is 'supposed to' be more efficient than electric.

Is it true, that with this system you need to get used to only using one hot water appliance at a time (shower or laundry, not both at once). Or is that simply not installing a large enough system?

I just don't know what to do! I'd like to be as energy efficient as possible, is this the way?

Thanks yet again for any tips!!

[tyusclan]

The propane models work very well, but the electric models do not. Depending on your hot water usage you may need to get one of the larger models or get more than one for different zones in the house where hot water is needed.

[Sawmill Jim]

Or get the wood fired boiled heat the house an the water an the cheapest thing known to man for the time your boiler is not used or elements in the same tank .

[DWIGHT DUNCAN]

I have one and its been a great change from the 40 gal propane water heater it replaced. We use nearly half the amount of propane as we did before installing this unit. But you do have to "learn" how to use it. Especially in winter when your hot water use in the shower is more senitive to changes in water temp.

The unit senses changes in water pressure to turn on and off. So if you are in the shower and the clothes washer comes on using hot water, then shuts off the hot water once the tub is full, that change in water pressure going throught the hot water line to the heater will cause it to shut off. You now get dowsed with cold water in the shower. But with some practice, you learn not to run other water-using appliances while you are in the shower. Now you have to get other people in the house to oblige as well.

I would never go back to a continuously heating water heater unless gas was free.

Just my 2 cents worth.

[Emmy D]

When I had one up North (in a rental) I tested it when I first moved in by taking a shower while my friend hand washed dishes. Plenty of hot water for both and no change in pressure...this was a Bosch model but I can't remember what model #.

Emmy

[painterswife]

We have one a love it. It does need an adjustment of how you use hotwater.

if you are the type that turns hot water on and off constantly while doing cleaning or dishes you will not be as happy with the "slug of cold water" in between firings.

If you like taking a long hot shower after 5 people have gone before you, you will be in heaven.

[Macybaby]

We installed one in the summer kitchen and it works fine in that application, but after having it I would think long and hard about having one for the entire house. We have a 50 gallon Marathon electric water heater in the house and it only costs us about $10 a month to use.

The main problem we have in the summer kitchen is restricted water flow. The heater needs a decent flow or it will not turn on. I need to turn the hot water on full (never a trickle) and then adjust the cold to get the right temp, however if I turn the cold more than about 25% open it lowers the flow to the heater and it shuts off. I've turned the heater down so that I won't scald myself. It would be great for something like filling a whirlpool tub but I'd hate it for normal washing up or doing dishes. I think for house use, I'd run seperate 3/4 lines - one for the cold and one for the heater so that turning the cold on would not have a big effect on the hot flow, and I'd strongly consider using point of use ones instead of the large full house type. My kids are grown so it's just DH and I and that also would influence my decision. If my daughter was till living with us, I'd maybe put one for the bathroom she used and keep her from using all the hot water out of the tank! Mabye but a timer on it too so after 30 minuite shower she'd run out of hot water - or limit it to only two shower uses a day . . . Teenage girls can go through a lot of hot water!

Cathy

[Callieslamb]

actually, you only have to worry about using appliances at the same time that use HOT water. I do most of my laundry in cold. And you would only have to consider the Dishwasher if it was filling. I easily took a shower with both the laundry AND DW running with ours.

[byexample]

We use on demand hot water (propane) in one of our buildings and like it fairly well. It's definitely an energy saver when compared to a traditional hot water tank heater.

Your average hot water heater is an entirely silly device in my opinion. It constantly consumes energy day and night keeping 40 gallons or more of water hot just in case you might want a little hot water. Studies have shown that as much as 85% of the energy these silly contraptions consume is released out into your home in the form of heat loss. If you are using air conditioning... you are paying extra money to pump the waste heat from the hot water heater back out of the house.

I've torn apart many hot water tanks (salvaged for solar hot water) and there's only about 1/2 inch of crappy fiber glass insulation protecting the darn things. My insulated coffee cup is more energy efficient.

If you do choose to go with the traditional hot water heater PLEASE consider installing a timer that shuts it off at night and during the day when you aren't there. It makes no sense to just keep dumping energy into 40 gallons of water throughout the night just in case you want to wash your hands in the middle of the night.

At least with on-demand you are pretty much only paying to heat the water you are using... so there's much less waste. And that has to translate into saving money.

There are various sizes of on-demand available. The smaller and less expensive models will likely only support a single use... but the larger models are designed to support multiple uses at the same time.

[madness]

I've used a propane one in a rental and didn't find any problems with it.

We have a small electric on-demand in the cheese kitchen for washing dishes. I HATE it. You can only have the hot water on - not cold and hot to adjust the temp - it has to be hot all the way or the breaker on the unit throws. Even with the hot on full blast, sometimes it doesn't seem to come on. Then 5 seconds later, it scalds you, then back to cold. It doesn't always do this, but I'd say once a week it send me into a rage! It was a super cheap model from Home Depot.

But again, I only hear good things about the propane ones. I wish we had gotten a tank just for that!

[cowboy joe]

The electric models will cost you a fortune to put in due to the wire size. I bought a small one (one sink / shower at a time). If memory serves, the current draw was so large that the unit required 6 AWG (at ~$2+ / ft) plus a 50 amp breaker. Can't imagine what the install requirements are for a larger electric unit. Getting ready to sell the electric unit so i can buy a gas model now that I have gas run to the house. My hot water take was manufactured in the 1970s so it's only a matter of time before it goes.

[cfabe]

I do not have one of the units but I have researched them quite a bit. I think they can be a nice solution, but there is a lot more thought to planning the installation than a regular storage water heater. Some things to consider:

They are sized based on hot water flow (Gallons per Minute) and temp rise. You need to know your incoming water temp and desired hot water temp & flow. Anyone who suggests a model without asking this information isn't doing you right.

They are WAY higher BTU/h than a normal waterheater. This means you may have to upgrade your electric service, gas line, propane regulator, or exhaust vent. Make sure you price out these changes.

There is some evidence that they don't work well with hard water or well water due to the heat exchangers plugging up. Some manufacturers void warranty if not installed on city water.

There are different control methods in use on the heaters. If you want it to heat water when you just run a trickle, make sure it can do that. Some of the gas models require electricity for control, some do not.

In theory, the electric ones will be 100% efficient while the gas ones are more like 80-90%. But consider fuel costs as well to determine which is lower cost.

Consider the affect of the heat loss of your current storage tank. If you keep it in a heated area of the house, the lost heat helps heat the house, so it's not really lost at all. Of course if you live in a mostly A/C area, the heat loss costs you more in A/C.

Good quality modern storage tanks are very well insulated. A lot of the data the tankless manufacturers use is based on older heaters. Depending on your fuel cost, the payback time may be a lot longer than they suggest.

[Shagbarkmtcatle]

We are plumbers and we do not install them. Why, first for the electric ones, you need the power company to upgrade the electric as the water heater demands more power when in use than what is found in a normal house.

The gas ones work if you have more than one. They still can only heat so fast and when using the shower, the washer, the kitchen sink and other appliances, how much hot water will you get at one time?

It's not been easy for people to get replacement parts. That's mean you end up with unsatisfied customer's.

We are using them in our cabin but we have what is called point of use water heaters. One in the kitchen for under the sink. ONe in the bathroom for water usage there.

[roachhill]

I read an article recently that pointed out the amount you save going to an instant heater depends on how much hot water you use each day. The more you use the less you will save. If your a real hot water hog you will use just as much gas for an instant heater. It doesn't effect me as I use very little hot water but it's important to note. I'm surprised most articles don't tell this particular fact.

[Dexter]

LOTS to think about here.
Thanks for all the tips, and things to consider!

[Sawmill Jim]

Have always said a timer on a water heater was a joke never took the time to prove it though . If there is little heat loss no gas electricity are used till the water temp drops inside the tank . So how many Kw would it take to reheat verses letting the t stat do it's work . Nother thing been sold is the two element water heater only one works at a time . Lower element is simplest an works just as well . Reminds me i put a lower element in mine 110v last winter to run on the generator an have forgot to change it back . I'll put it on my list .

[frank]

I bought a Tempstar 15 elec on demand htr and used it with Garys solar system. The tempstar accepts pre-heated water and doesn't turn on until water is less than 95 degrees. Mostly it is off (two 40 amp breakers) because the solar works so well. I love it.

[Old Vet]

I have an electric one on my front porch that you can have if you will pay the freight for it.It takes two circuit to run one is a 50 amp and another one 30 amps. The 50 amps only runs the heater and the 30 amp will run the controls. I found out that you will need several of them not one if your bathroom is in another place except across the wall from the kitchen. If your kitchen is 30 feet from your bathroom where do you place it? Not where the large tank is. It is too far from where it will be used. I have two bathrooms one at one end and another in the middle of the house and the Kitchen in the middle and a laundry room in between. If I were to use one it would take two and it would have to be placed one in the bathroom and in the laundry room.

[CJ]

It's been years since we've used them but when we lived in Germany we had them, one in the kitchen, and one in the bathroom. I thought they worked very well.

[snoozy]

I've had a propane Aquastar for 11 years. Works just great. I'm very happy with it. I'm on well water. Some plumbers whined about putting them in even then, but we had them do it and it works fine.
ZERO problems.