Smaller, much cheaper tankless water heaters?

[FiftyIsTheNewTwenty]

We have the usual, single tank water heater for the whole house.  The master suite bath is like 60' away, so it takes a long time for hot water to get to that shower.  Also, the water heater takes up half the front hall closet, and I'd love to get that space back.  So I've been thinking about tankless:  two units, one for each end of the house.

High-capacity, whole-house tankless units are expensive, but there are smaller ones with 4 gal/min capacity for under $400, like this:  https://www.amazon.com/Rheem-RTE-13-Electric-Tankless/dp/B003UHUSGQ.  And for only one shower at a time, working around laundry or dishwashing, I could probably go even smaller.

Two of these are cheaper than one big tank unit.  Labor is not an issue.  Why not go this route?  Why don't more people do this?

[Spork]

If my electrical calculations are correct (and I'm bad at making incorrect calculations... check me!)....  A 13,000 watt/240v heater is 60 amps.  If you have 2 of them installed, running ... its 120amps.

My first thought is: is your electrical panel and service capable of handling 120amps more than it already is handling?

I know most folks do not put in electric inline heaters because of the required current draw.  A plumber friend of mine says he (a) didn't care for the electric versions and (b) wouldn't put them in unless the house had 400amp service.

Do you have any access to gas/propane? 

[SwordGuy]

We have a natural gas tankless heater and love it.   

I don't think you'll see as much savings if you have a propane tank or use electric ones.

[Spork]

We have a natural gas tankless heater and love it.   

I don't think you'll see as much savings if you have a propane tank or use electric ones.

Yeah, we're on propane and it's ridiculously expensive.   You'll save a couple hundred bucks a year (in theory*) with an inline propane vs a tank propane and a theoretical minimal amount over electric/tank but you're much better off with natural gas.  Unfortunately for us, you'd have to live one mile closer to town to get natural gas.  It doesn't come down our road. 

*I say "in theory" because, with a tank you get your ass out of the shower when the hot water runs out.  With tankless, hedonistic adaptation sets in and "just a couple more minutes and I'll get out"...  I think sometimes you burn up your savings in longer showers.  And it takes quite a few years to actually get any real savings once you pay extra for the tankless.

[paddedhat]

Spork is right about the load requirements. They draw 54 amps according to the spec. sheet and need a 60 amp breaker and a #6 copper as supply wire. The reason electric on demand isn't very prevalent is that it draws HUGE loads and often require a bigger incoming electric service than typical. Will two of them work in your case? maybe, but if there are two running, and an electric stove, dryer, or any other combination of heavy loads attempting to operate at once, it might not end well.

[FiftyIsTheNewTwenty]

If my electrical calculations are correct (and I'm bad at making incorrect calculations... check me!)....  A 13,000 watt/240v heater is 60 amps.  If you have 2 of them installed, running ... its 120amps.

My first thought is: is your electrical panel and service capable of handling 120amps more than it already is handling?

I know most folks do not put in electric inline heaters because of the required current draw.  A plumber friend of mine says he (a) didn't care for the electric versions and (b) wouldn't put them in unless the house had 400amp service.

Do you have any access to gas/propane?

There's already dryer/appliance service at both locations, but it's probably the standard 30A.  I don't know about the whole house but I'm sure it's nowhere near 400A!  Or even 200A, which might be fine.

I would do natural gas in a heartbeat if we had it.  Propane might make sense if starting from scratch with the furnace and other appliances, but not just this.  I do need a new HVAC system but I'm going for a mini-split.

The current tank unit works fine.  I'm looking for more storage, and faster hot water in the master.

[Spork]

One thing I've seen builders do around here with houses that are widely spread:  They buy a tiny little 10gallon water heater and put it at the far bathroom.  When they plumb it, they feed it with the hot water from a larger tank upstream.  This gives faster hot water at the distant location, but backfills it with water that is pre-heated.

[lthenderson]

I haven't gone tankless because in our area, the life expectancy of a tankless water heater isn't significantly greater than the traditional tank model but the price is significantly higher. The last time I replaced my tank water heater with another tank water heater, it was at a cost savings over a tankless even if I calculated efficiency gains and assuming like Spork said, one doesn't adapt and use even more hot water.

[Spork]

We pretty much convinced ourselves we'd save money with a tankless (over time) when we built our house.  In hindsight, I think it is probably not the case.  Maybe it's a break-even.  And that's a maybe.  I do really like the concept of infinite hot water.  I like the minimal space it takes to install.  (We've got 2x4 construction with brick veneer.  Ours fits in the wall cavity between interior drywall and exterior brick veneer.)  I like being able to go crank the temperature up to max at a moments notice when I want to scald the crap out of something (like washing wine bottles before bottling.)

But like I say: in retrospect it seems more like a luxury item than a money saving item.  I still might go that direction again.  It's worked well.  But it is a more complicated bit of equipment and I do expect at some day the complicated mechanism is what will bite me.

[FiftyIsTheNewTwenty]

One thing I've seen builders do around here with houses that are widely spread:  They buy a tiny little 10gallon water heater and put it at the far bathroom.  When they plumb it, they feed it with the hot water from a larger tank upstream.  This gives faster hot water at the distant location, but backfills it with water that is pre-heated.

I've seen this too.  I wonder how this would work with a tankless model, especially the newer ones with (supposedly) accurate temperature control.  It shouldn't take much power to give a much smaller boost.

[Spork]

One thing I've seen builders do around here with houses that are widely spread:  They buy a tiny little 10gallon water heater and put it at the far bathroom.  When they plumb it, they feed it with the hot water from a larger tank upstream.  This gives faster hot water at the distant location, but backfills it with water that is pre-heated.

I've seen this too.  I wonder how this would work with a tankless model, especially the newer ones with (supposedly) accurate temperature control.  It shouldn't take much power to give a much smaller boost.

I can't say how well it works, but I've seen it done.  We looked at model homes/builder shows for years before we finally built ours.  Where we saw it done was a huge monstrosity with one bath way down on the other end in a different zip code from the tankless.

[bacchi]

*I say "in theory" because, with a tank you get your ass out of the shower when the hot water runs out.  With tankless, hedonistic adaptation sets in and "just a couple more minutes and I'll get out"...  I think sometimes you burn up your savings in longer showers.  And it takes quite a few years to actually get any real savings once you pay extra for the tankless.

This is always a "con" for tankless heaters. We only drain the 40 gallon tank when we run the clothes washer and then take 2 showers immediately after -- the 2nd person always gets some cold water during rinsing. Do people actually use all of the 105 degree water from a 40-50 gallon tank with one shower?

[Spork]

*I say "in theory" because, with a tank you get your ass out of the shower when the hot water runs out.  With tankless, hedonistic adaptation sets in and "just a couple more minutes and I'll get out"...  I think sometimes you burn up your savings in longer showers.  And it takes quite a few years to actually get any real savings once you pay extra for the tankless.

This is always a "con" for tankless heaters. We only drain the 40 gallon tank when we run the clothes washer and then take 2 showers immediately after -- the 2nd person always gets some cold water during rinsing. Do people actually use all of the 105 degree water from a 40-50 gallon tank with one shower?

You can do it pretty easily if you get all cozy in the shower and something else is using the water (washer, second showerer).

105??? Damn you keep your water heater cold!  I believe you need to keep it at 140 to keep bacteria from growing in the tank.

And... you don't have to use all the 40 gallons to notice.  Remember that when you pull 1 gallon of 140 degree water out, it's replaced by 1 gallon of cold.  In the winter that's probably in the 60s in the south and colder in the north.  So... if you use half of that 40 gallons, your 140 degree water is probably around body temperature -- and that is at FULL hot.  (There is some amount of pooling of hot near the top and cold near the bottom, so it isn't exactly an average of the two temps like I imply... but at half replacement, it is very noticeable.)

[lthenderson]

We have a 50 gallon tank and usually can get everyone through a shower without running out but we have ours set quite a bit north of 105. If I had it set that low, perhaps I would go through more hot water per shower because the mix would mostly be hot water.

I hate weak showers so the first thing I do is drill out the shower head low flow reducers they put in. It is much easier to go through 50 gallons of water that way than with them left in.

[maradits]

I have the "Ecosmart ECO 18" tankless electric water heater in my house.  You can find them on eBay or amazon for under $400 shipped (cheaper than buying a traditional water heater at your big box store.

My comments are:
-It heats up quickly and it on par with the few seconds it would take to get hot water at any faucet with a traditional heater.  I do notice a drop in temperature if I'm in the shower and my girlfriend is washing dishes or something... but it's pretty easy to time our use to not conflict.  I kind of wish I would have got the ECO 24 which is the next size up model, but I can live with it.
-It takes some pretty substantial electric to power it.  The ECO 18 is 18kw and requires an 80 amp circuit.  This meant running 4 #8 wires which could be challenging depending on your situation.  I was rehabbing my whole house and installing a 200amp electric panel so it wasn't a big deal.
-It's awesome not heating water all day for no reason.  I don't know exactly how much power I save because I installed it before I ever lived in the house, but I have to believe it's a fair amount.
-It takes up virtually no space in the basement and doesn't need to vent like a gas heater which is nice.

[ncornilsen]

At the recommendation of, I believe, bakari on this forum, I put a 400 dollar aquah brand heater... mainly to reduce the wait time for hot water. I have natural gas and would not recommend one if all you have is electric.

[FiftyIsTheNewTwenty]

I have the "Ecosmart ECO 18" tankless electric water heater in my house.  You can find them on eBay or amazon for under $400 shipped (cheaper than buying a traditional water heater at your big box store.

My comments are:
-It heats up quickly and it on par with the few seconds it would take to get hot water at any faucet with a traditional heater.  I do notice a drop in temperature if I'm in the shower and my girlfriend is washing dishes or something... but it's pretty easy to time our use to not conflict.  I kind of wish I would have got the ECO 24 which is the next size up model, but I can live with it.
-It takes some pretty substantial electric to power it.  The ECO 18 is 18kw and requires an 80 amp circuit.  This meant running 4 #8 wires which could be challenging depending on your situation.  I was rehabbing my whole house and installing a 200amp electric panel so it wasn't a big deal.
-It's awesome not heating water all day for no reason.  I don't know exactly how much power I save because I installed it before I ever lived in the house, but I have to believe it's a fair amount.
-It takes up virtually no space in the basement and doesn't need to vent like a gas heater which is nice.

Hot water is our second biggest electric user, at $50-60/mo.  I don't know how much of that is actual use vs. just keeping the tank hot.

I rarely use hot water for laundry -- maybe warm in winter when the water is so cold.

Thanks everyone for your replies!

[Spork]

Hot water is our second biggest electric user, at $50-60/mo.  I don't know how much of that is actual use vs. just keeping the tank hot.

They're probably not the same efficiency, but I can give you a wild ass guess baseline.  I have a 50 gallon electric water heater in my shop.  Back in the days before it was my shop, it was a weekend getaway.  We learned that if the building sat still for a month, it cost about $30 in electricity to keep the water hot.  We also learned to flip the breaker for the water heater before we left.

[paddedhat]

105??? Damn you keep your water heater cold!  I believe you need to keep it at 140 to keep bacteria from growing in the tank.

105* is NOT hot water, it's actually on the low side of warm. It is can also be extremely dangerous, as it will allow potentially fatal bacterial growth in the tank. In fact temps that low can create a wonderful environment for legionnaires disease, which is commonly misdiagnosed as pneumonia, and can be deadly. The problem with a safe temperature in the tank, is that it's too hot to safely flow at the faucets, especially if there are young children or frail elderly folks present. The cure is a mixing valve installed after the heater to mix cold water into the 140* output of the heater. This also provides the benefit of providing more usable hot water output from the tank.

[younggunner]

Rinnai makes a fantastic tankless water heater.  I would definitely recommend looking into that brand.  Aside from running gas lines and vent lines (if not there already) the install is actually very DIY friendly.  I think i spent roughly 1100$ on mine 3-4 years ago and it's great.  Spent less per month on gas bills and never ran out of hot water.  Also you can turn the water up super hot if you are like my GF and like to shower in boiling hot water...

[Spork]

Rinnai makes a fantastic tankless water heater.  I would definitely recommend looking into that brand.  Aside from running gas lines and vent lines (if not there already) the install is actually very DIY friendly.  I think i spent roughly 1100$ on mine 3-4 years ago and it's great.  Spent less per month on gas bills and never ran out of hot water.  Also you can turn the water up super hot if you are like my GF and like to shower in boiling hot water...

And if you are in a climate that supports it.. vent lines are not even necessary.  Ours mounts in the outside wall and direct vents out the side of the unit.  I suspect you can't get away with this in northern climates.

...but they're not exactly cheap.

[Doggybutt]

I have an ECO SMART 24 (I think) and it was cheaper than a 40 gallon gas water heater when I bought it on sale.  It draws 120 amps-- I upgraded my box from 100 amp to 200 amp, but the wires coming in from the meter are #2 aluminum, so I'm not getting much more than 100 amps coming into my house.  Once I upgrade to copper wires it should be fine, but it's worth checking out whatever you've got going on electrically before making the plunge.

I absolutely love tankless water heaters, due to their size, performance, and simplicity, and the electric performs similarly to the gas one I had in my old house.  The technology and price point has improved a lot in the last several years.  Tankless heaters get more efficient the more frequently you use them (because you're not having to heat the coils and water sitting in the pipes as much), so a family of 7 will see more savings than a single person.