@jbow... Yeah, man. Definitely take another look at that situation. Convenience is great but there probably are far better and cost effective solutions to your dilemma... like the point of use units.

@Robert... That's cool. Like I said I don't know the math and I'm sure the tech has come a long way since I last looked into them. Still though if someone can afford a small PoU unit at the end of a long run obviously that solves the whole problem. Far more environment friendly too. I think the code problems back when I was thinking of buying one was the circuit stuff... at least for the big ones. They just had such a draw you had to install a special line and breaker for it all. Is that still the case or can they run on 220 lines?

Jeff Evans


I am assuming then you guys don't have gas as well as electricity. The ultimate way to go is a gas heater that only turns on when you need the water and it heats it on the go. You never run out then. But this is only good of course where gas is available. 

How many gallons of hot water per minute can those systems nowadays  produce? I've seen such long ago (in the UK) but the ones I saw were tiny ones - one unit for the bathub, one for kitchen etc. and they were ridicilously inefficient. It took an hour to fill the bathub, and then the water had already cooled down.
 
How reliable are they in the long run nowadays? I remember reading about the amount of maintenance they require and how dangerous they can be in case of failure.
LATE ADDITION: I've never seen one in Finland, and we have a rather cold climate. So I assume there's a reason no-one uses those here.

Electric water (resitive element) heaters are effectively 100% efficient at transferring the heat to the water, so better insulation etc. is the only difference between them in that regard. The price is mainly due to the cost of materials and construction-a more expensive heater may last longer (or not).

Gas heaters can be designed so that less heat is lost up the flue, but the cost may not reflect that. 

An "instantaneous" heater (gas or electric) in which the cold water flows through heated coils does not lose heat when not in use and offers a significant energy saving in most cases. But it requires more power or combustion when active so the heating elements/exchanger are more expensive to make. 

If you live in a warm climate, a heat pump (reveres air conditioner) unit can save substantial energy, but the cost is much more than other water heaters, and there is probably going to be more maintenance (repair) cost over the life of the unit. If your water heater is sitting in a really cold place, then the efficiency drops to the point that many of these units are made with auxiliary electric heating coils that take over when the garage is too cold to provide the temperature difference the heat pump needs to function. The energy efficiency specifications of these units need to be interpreted carefully. A unit in a Florida shed will have quite different actual savings than one in an unheated Minnesota garage in winter. If you put one in a heated area, then you are actually paying for the heat that is transferred from the room to the water, so the real efficiency is much less.

RobertB

Even in an extremely large home, at worst, you will waste a quart of unheated water.

My home certainly isn't huge ... ~2000sq. ft.  The kitchen sink is at one end of the house and the water heater at the other.  I have to run close to 1.5 gallons of water before the water coming out the tap is actually hot.  But the worst part is that when done washing dishes, or whatever, I've heated close to 1.5 gallons of water that will just sit in the pipes and cool off.  What a waste of energy.
 
I'm looking at installing one of those small tank 120V heaters to put under the kitchen sink.  Doing dishes rarely uses more than a gallon of hot water anyway.  99% of the time, the convenience of having instant hot water would outway the inconvenince of only having a limited amount available.

dmbaer

RobertB

Even in an extremely large home, at worst, you will waste a quart of unheated water.

My home certainly isn't huge ... ~2000sq. ft.  The kitchen sink is at one end of the house and the water heater at the other.  I have to run close to 1.5 gallons of water before the water coming out the tap is actually hot.  But the worst part is that when done washing dishes, or whatever, I've heated close to 1.5 gallons of water that will just sit in the pipes and cool off.  What a waste of energy.
 
I'm looking at installing one of those small tank 120V heaters to put under the kitchen sink.  Doing dishes rarely uses more than a gallon of hot water anyway.  99% of the time, the convenience of having instant hot water would outway the inconvenince of only having a limited amount available.

Now that I've seen places with this type of heater (the small, by location type) I completely agree.  Plus, there's always the laziness issue that it's nice not to have to wait to get that hot water.

Janet... a few years ago, our old gas water heater (40gal tank) was giving problems. 

I pulled it out and disposed of it. (wish now I had heard of the water tank rocket experiment...... oh well)

Since I was doing the work myself.... the option to replace or upgrade was on the table. 

I opted to install one of the TANKLESS Instant water heaters. I bought it at Lowes. It was more expensive than a tank model BUT..... it also had tax rebates and it was so much smaller.... I gained several new shelves of closet space where the old tank used to set. 


It was a few hours of re-plumbing some water lines, and removing the old gas line. I also needed to install a new electrical circuit to supply it.

It heats the water so hot that you can not hold your hand under it..... in seconds. It still takes the same amount of time for the hot water to reach the kitchen sink but no problem there...... and the water heater only runs when water is flowing at a certain level of flow.  Temp & flow are adjustable. It is a 2 stage water heater. So if you have a faucet with a drip leak on the hot side.... you are leaking cold water, not heated water. 

When I go on vacation or off for the weekend.... I no longer have to shut the water heater off to save money. 

It's about the size of a normal computer case..... not very big compared to the tanks. 

If you can work on plumbing and electrical yourself or have a competent friend who can help, this is the way to go.

For me, the total time for the removal, re-installation of the new tankless, plumbing and electrical was one day... working by myself.

dmbaer

RobertB

Even in an extremely large home, at worst, you will waste a quart of unheated water.

My home certainly isn't huge ... ~2000sq. ft.  The kitchen sink is at one end of the house and the water heater at the other.  I have to run close to 1.5 gallons of water before the water coming out the tap is actually hot.  But the worst part is that when done washing dishes, or whatever, I've heated close to 1.5 gallons of water that will just sit in the pipes and cool off.  What a waste of energy.
 
I'm looking at installing one of those small tank 120V heaters to put under the kitchen sink.  Doing dishes rarely uses more than a gallon of hot water anyway.  99% of the time, the convenience of having instant hot water would outway the inconvenince of only having a limited amount available.

True enough.
I thought about that after I wrote it. That's what I get for trying to think after a 15 hour day.
Depending on how the house is plumbed (size of pipe/length of runs) there is a variable on how much water has to be purged before hot water gets to the point of use.

Janet... the one I installed was a whole house tankless....

they also make "at the source" tankless. these are smaller and mount under the sink to provide instant hot water at the bathroom, kitchen or shower/tub. 

This route removes the wait for hot water, but raises the installation cost since every location where you need hot water would require it's own heater..... and circuit.

Kalle Rantaaho

Jeff Evans


I am assuming then you guys don't have gas as well as electricity. The ultimate way to go is a gas heater that only turns on when you need the water and it heats it on the go. You never run out then. But this is only good of course where gas is available. 

How many gallons of hot water per minute can those systems nowadays  produce? I've seen such long ago (in the UK) but the ones I saw were tiny ones - one unit for the bathub, one for kitchen etc. and they were ridicilously inefficient. It took an hour to fill the bathub, and then the water had already cooled down.
 
How reliable are they in the long run nowadays? I remember reading about the amount of maintenance they require and how dangerous they can be in case of failure.
LATE ADDITION: I've never seen one in Finland, and we have a rather cold climate. So I assume there's a reason no-one uses those here.

Kalle, we have one unit which services the whole house, including taps, shower/bath & central heating.

As long as they are serviced regularly the modern units rarely suffer from failure, and the entire family can take back to back showers with absolutely no temperature roll-off.