O/T tankless water heaters

Anybody using them? Are they more efficient that a regular water heater?
Our energy bill is about $100 a month, all electric, guessing that the water heater alone is responsible for 50%-75% of this.

They are much much more efficient, but you need to have the juice to run them.

The Rinai tankless gas units are very efficient they can also work on propane

Much more efficient than tank types, but much more up front costs. You pretty much need on for each useage area, bath kitchen, etc. A dedicated electrical circuit for each one and they are not cheap either.
Also if you have heavy mineralized water they do not last as long as a tank type from what I have seen.

Same efficiency. They win when placed next to the point of use. They save running water from cooled down hot water pipes.

Do some research. Mr. Buick-and -Deere is right-on, 100% correct. There is no gain unless you've got a distance problem. It takes very little energy to keep a tank of water warm - and tank heaters are cheaper and easier to put in. Every use a Thermos bottle? How much heat does that use to stay warm?

Now, if you have a remote bathroom somewhere, 50-100 feet from the tank heater - then you will gain some efficiency by using a spot heater at that one site.

Most of what you hear is pure hype - including the testimony from Paul Harvey. The instant heaters are overly expensive to buy, and difficult to intall. They need big wires - or big gas pipes.

One other problem also - with instant heaters. If you preheat any of your water with solar - or a wood stove - the instant heaters turn on anyway and waste a log of energy. That is, unless you buy a special version that costs 20% more than the normal overpriced units.

Is your thermostat set really high on your waterheater? Alot of people crank them way to high so it uses alot more energy to heat and you dont need the water that hot, around 120 degrees is perfect.

do you have all the hot water lines covered in insulation? the ones you can reach anyways?

then tankless work good for when lots of hot water is needed.

guess it depends on your situation and setup. There is just myself and my wife in our house and we both work so no since in keeping a tank of water hot 24/7 for two showers in the morning. Those 2 showers would be quick also with the last one in getting a cool finish with 150 liters of water. We have oil central heating and I have a setup rigged so that when we don't need heat, I switch to the tankless. In the typical American household, there could be some question on the differences between tank and tankless. Here in Germany, dishwashers, clothes washers, etc are supplied with cold water and heat themselves when you use them so your water heater is for bathroom and kitchen sink. Sure is nice to be able to take a hot shower as long as you want or fill a tub with an endless supply of hot water.

Dave

We replaced out oil-fired hot water heater with an electric hot water heater last fall. It rasied our electric bill by $20/month and lowered our oil bill by $50/month. The new heater cost $600 with installation. Given the rise in fuel costs, I think it has already paid for itself. No kids though, just the wife and I, with more people the electric cost would be higher.

I've heard the electric ones have trouble. Thought about putting a Bosch NG model in when the time comes but we're only spending about $25/month for NG for our tank unit for 5 people (we were spending $12/month about 2 years ago) so I'm struggling with the cost turn around. they are nice as they don't take much room and we don't have alot of space where the old one was.

I put a big 190,000BTU Rinnai unit at my old work at a campground. I put it in the kitchen where they cook for up to 150 kids at a time. Far as I know it's worked out well. It was natural gas and needed 3/4" gas line and the venting is very expensive and you don't have much freedom for running the vent.

(quoted from post at 06:20:31 10/20/08) I've heard the electric ones have trouble. Thought about putting a Bosch NG model in when the time comes but we're only spending about $25/month for NG for our tank unit for 5 people (we were spending $12/month about 2 years ago) so I'm struggling with the cost turn around. they are nice as they don't take much room and we don't have alot of space where the old one was.

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There are simple ones and some pretty sophistocated models. Not sure what models are available to you folks, but over here, Bosch is the most expensive and kind of overated. If you can get ahold of a Siemens, they are pretty good. Ours runs on 480 volts and has 2 positions on the switch (on/off). Have it hooked up by the normal heater so it takes care of the whole house. Weighs about 10 pounds and is about the size of a briefcase. LG is also a good model. Are washing machines and dishwashers that heat their own water available in the States (affordable)?

Dave

A tank WH is responisble for 66% of energy used to keep the water hot. Any utility website will confirm this.

My son has natural gas tankless. At the opposite end of the house, it takes about 15sec of free flow before HW is felt.

Both the son & DIL are in people service jobs thus require two showers daily each. During the summer months, they don't use enough HW to receive a gas utility bill as the tankless doesn't use the minimum use requirement from the utility.

They both can take back to back showers then wash 10 loads of cloths and never run out of HW.

He's on there 7th year and he says he'll never go back too a tank type WH.

T_Bone

Dishwashers do, but I think most are hooked up to hot water lines anyway. Maybe the new higher end washers do.

We have used an electric one for for years Bosh and have a number of problems with the heating control. But they had a supplier problem and the latest unit has has been fine for two years. They always stood behind unit. Had a gas Bosch in Europe for three years which also heated apartment. Never any broblems with this one. The guys are correct it does take heavy wiring (3, 30amp 220V breakers). I thinkgthey are worth the money in eventual savings and you do get a tax break from Fed's and maybe your state also. If you buy one get it off of the internet. The cost was significantly cheaper than the big box stores and plumbing suppliers.

I keep hearing tankless advocates talking about all the loss involved with tank-heaters. I don't believe it; in many cases it's not true.

A well insulated electric tank heater loses about .5% to 1% of its heat, per hour. So, a well insulated 40 gallon tank heater wastes about 5 gallons of hot water per day.

Average USA family uses 50 gallons of hot water daily. That results in 10% waste due to thermal loss while keeping 40 gallons hot all the time. That's not very much loss and results in a 90% efficient heater. It's also the reason why well insulated tank heaters are rated just about as high as tankless heaters when it comes to the efficiency numbers - if you read specs from unbiased sources. Tankless heaters also waste some energy - it does NOT all go to heating water. Consumer Reports did a study on tank heaters versus tankless and found no overall savings for most installations. I'll add this disclaimer - I don't tend to trust Consumer Reports without doublechecking, but I do agree with these findings.

A house with a family living in it - with one tankless heater needs something like a 3 1/2 GPM unit with a 55 degree temperature rise. That means if your cold water is normally 55 degrees F, the tankless heater will warm it up to 110 degrees (raises the temp by 55 degrees). To install, it requires a 120 amp, 220 volt circuit (more than some entire houses have).
So, you've got the cost of the electrical installation, plus the $600-$700 for the new heater - about twice what a tank heater costs.
I'll also add that parts for electric tank heaters are usually generic. If a part fails, like an electrode, upper or lower thermostat, I can go just about anywhere and get a new one. Not so easy with some of these tankless heaters.

As Mr. Buick-and-Deere stated earlier, there are certain type of applications - especially with long pipe runs, where a point-of-use tankless can save some money.

Another aspect of most tankless heaters that I regard as a downside is . . . they don't have thermostats. So, if you feed them with preheated water, they STILL come on and waste energy. This can be avoided by ordering "special" tankless heaters, usually made for the solar market.

I saw a renovation show with a whole house tankless. For the long runs they had a valve that senses the water temperature and would would recycle the water till the hot water got there. Seems like a few 110 at location would be better than a whole house.

I installed a tankless electric at a remote building at the museum site that my wife helps run. Building is over 100 feet from the main, tank hot water heater. Even with a well insulated feed pipe, you had to run the water for five minutes before any hot water came out - and even then - it was only luke-warm.
In this case, the tankless works great. Had to run a new electric service for it, though. It's a small, under-sink 1.5 GPM unit and required a 240 volt/20 amp circuit. There was a smaller unit available that only required a 120 volt/30 amp circuit - but it did not warm cold well water enough to be useful.

In regard to tankless heaters and thermostats - most don't use them, but you can special order them that way. The most common tankless units use a flow-valve and will rise the temp of any incoming water. Higher priced thermostat-controlled units sense water temp and can shut themselves off. Also, some higher price units have low-rate flow valves so you can use them in low-flow water systems.

For years, tankless heaters were a problem when used in certain off-grid, solar-electric homes. That because they often have both low-flow water, and also preheated water from solar panels and/or wood fires.

I read all the posts here and none of them mentioned that there is a regular mantinence schedule that has to be performed on tankless water heaters.

Jim