Tankless water heaters are terrible....

[BrettS]

What bothers me is when tankless heaters are marketed as 'more efficient'.

I think that's just a marketing term that you have to take with a grain of salt. Tankless heaters are more efficient than some options. They just aren't 'most effecient'. But that's really the case for everything... it depends on what you compare it to. A tesla is a 'more efficient' car, but if you really wanted to save energy you would drive a smart electric car or maybe just use a horse and buggy. Those would be a lot less convenient, but if efficiency is your only goal....

If unlimited hot water is the goal then ideally you could put a tankless heater downstream of a heat pump heater... best of both worlds

That's actually an interesting idea and made me think for a minute, but I just checked and I used a total of 62kWH to heat water last month. I pay about 13 cents/kWH, so I only spent $8 on hot water last month. It would be a pretty long payback period to add a heat pump water heater.

 

[israndy]

I would think the BEST is a hybrid. Turn your tank down, especially during freezing times, and rely on the tankless to make up the difference. I feel SO guilty about leaving my cabin's tank heating during the winter. No easy way to turn it down remotely when we cannot get there due to snow blocked roads. So if I left it at 80 degrees and got a tankless to go the rest of the way and mount it inside the house at the bath/kitchen nexus, that seems like it would be efficient all year long.

-Randy

 

[nwdiver]

That's actually an interesting idea and made me think for a minute, but I just checked and I used a total of 62kWH to heat water last month. I pay about 13 cents/kWH, so I only spent $8 on hot water last month. It would be a pretty long payback period to add a heat pump water heater.

Yeah... you really need to have 4 people using hot water for a replacement to make financial sense... I like long hot showers and wanted to get rid of the gas service that was costing $15/mo just to keep it connected so paying $500 more for a heat pump was worth it. An added fringe benefit is that in areas with hard water you don't get scale in a heat pump since the coil temperature doesn't exceed ~140F.

 

[BluestarE3]

I have had a Takagi gas tankless water heater for over 5 years and it has worked well and reduced my NG use. I can't provide any hard numbers.

In the future I plan to replace it with either a heat pump or an electric tankless but haven't done much research yet. This thread is interesting.

Years ago, when our kids still lived at home, running out of hot water was a common occurrence as we all got ready for work and school at about the same time. That's when I had considered getting a tankless water heater; however, I had just replaced my traditional tank heater a few years earlier (emergency replacement due to the old one springing a leak) and couldn't justify the cost of switching.

Nowadays, because of the drought, my wife and I have been taking Navy showers for the past several years, so as a consequence, we don't use much hot water for bathing.

 

[wws]

What about gas tankless water heaters... are they terrible as well?

Gas tankless are great. I had two Rheem units installed in our house nearly ten years ago, and we really like them. Much lower cost of operation than electric ones.

We installed ours as part of a major re-construction project, so the extra piping wasn't a big deal. The main reason I installed them was so I did not have to dedicate valuable square footage for a closet for a tank. They just hang on an outside wall where they are out of the way. (No basement or attached garage here.) My only regret is that I should have installed one closer to our kitchen. Would still be easy to add one though.

A solar hot water heater would be fun to try. But I can't imagine it would save much money over the gas tankless. And I'd also need to find space for that tank again...

 

[nwdiver]

A solar hot water heater would be fun to try. But I can't imagine it would save much money over the gas tankless. And I'd also need to find space for that tank again...

Solar hot water heaters have been rendered pretty much obsolete by cheap PV... unless you go the Central American route and put a black barrel on your roof.

A heat pump water heater reduces your electric use by ~70% and cost ~$1k. Most solar hot water heaters cost >$3k.... so it's significantly cheaper to just install a heat pump and a few PV panels to have the same net effect as a solar hot water heater. With the added benefit that if you're on vacation you can actually export electricity instead of having hot water sit in a tank unused.

 

[McRat]

In a perfect world, the second you turn on your hot water faucet, out would come water that is at full hot water temperature. Because the last time that faucet produced hot water, there was hot water all the way to the valve.

That isn't what we experience. The water cools down in the piping. Sometimes fast, sometimes slow, but it does. So all the cold waste water that comes out of the faucet before you get hot water, used to have hot water energy stored in it. Filling a bathtub or sink or washing machine does not negate that, it just saves fresh water. That heat was lost for good and you must compensate with more gallons of 'hot' water to get to the same temperature.

A small, on-demand, local hot water heater, does pretty much supply instant hot water. Much of the efficiency gains are due to the lack of piping losses, not just storage tank losses.

 

[miimura]

When I had my house built 4 years ago, I looked at solar hot water and the costs just didn't make sense. I decided to go with a Navien tankless gas water heater. I also had all the hot water pipes insulated with a recirc loop. The Navien has an internal variable speed recirc pump so it uses that as an additional control variable to ensure consistent output temperature. It also has a built-in timer so you can turn off the recirc during overnight hours, or whatever schedule you want. I get hot water out of my shower in 4 seconds and the kitchen sink in 6 seconds. The only improvement I would make would be to integrate the water heater with a Smart Home system so that it would know when everyone was away and run even less.

 

[brkaus]

If unlimited hot water is the goal then ideally you could put a tankless heater downstream of a heat pump heater... best of both worlds

I've been considering this. I wish they made a heat pump water heater designed specifically for this application. Without the high current resistive heat elements, I would have capacity my my electric panel to do it... My plumber & electrician we

That's actually an interesting idea and made me think for a minute, but I just checked and I used a total of 62kWH to heat water last month. I pay about 13 cents/kWH, so I only spent $8 on hot water last month. It would be a pretty long payback period to add a heat pump water heater.

We live in a community with "monopoly propane", priced through the roof. Switching from two propane tanks in series to a single tankless dropped by propane bill from $120 -> $35 per month in cold months (water heaters are in cold attic).

 

[ecarfan]

A heat pump water heater reduces your electric use by ~70% and cost ~$1k.

Can you recommend a specific unit? I'm interested...

 

[nwdiver]

Can you recommend a specific unit? I'm interested...

The GE GeoSpring is the most cost effective but they've had A LOT of quality issues... not sure if they've worked them out or not. They do have a 10 year warranty so if you're in their service area they'll fix any issues under warranty. Rheem is the next step up. Both are readily available locally. GE at Lowes and Rheem is at Home Depot.

Looks like like the GE Geospring has a COP of 3.25 and the Rheem is 3.5

 

[hockeythug]

Fools tank's!

 

[Xenoilphobe]

You might want to read this report.. http://www.nrel.gov/docs/fy16osti/64904.pdf

 

[Xenoilphobe]

The GE GeoSpring is the most cost effective but they've had A LOT of quality issues... not sure if they've worked them out or not. They do have a 10 year warranty so if you're in their service area they'll fix any issues under warranty. Rheem is the next step up. Both are readily available locally. GE at Lowes and Rheem is at Home Depot.

Looks like like the GE Geospring has a COP of 3.25 and the Rheem is 3.5

Discontinued: GE pulls the plug on the GeoSpring heat pump hot water heater

 

[TexasTeslaRacing]

What about gas tankless water heaters... are they terrible as well?

I was going to ask the same question. We have tankless gas on our last two homes and it's been perfect. Rinnai and Rheem brands. It's great. Hot water all morning long. If you have a teenager you know how fast hot water can go if you have a traditional tank.

 

[brkaus]

You might want to read this report.. http://www.nrel.gov/docs/fy16osti/64904.pdf

Good info!

Discontinued: GE pulls the plug on the GeoSpring heat pump hot water heater

That stinks.

 

[Xenoilphobe]

Best Gas Tankless Water Heaters 2017: Top Reviews

 

[Merrill]

I need a new hot water heater and I am all electric, most of what I read about electric tankless is not good. Would be interested in any input.

 

[brucet999]

I guess I will jump in because I love mine and will install them in all future homes I own.

Mine is gas heated and our electricity bill even with the car is less than we were running when I lived in Texas with our traditional water heater. (Most of that is probably because we are in new construction built in 2010 with good insulation, thermal windows, radiant barrier, etc - its efficient enough that solar doesn't make $$ sense for us. My house in TX on the other hand was built in 1983.)

But honestly I don't worry about any efficiency standards for our tankless water heater - I love the endless hot water it provides. So it doesn't matter how many overnight guests we have and if everyone is taking a shower in the morning or if the dishwasher and laundry are running. Everyone has hot water.

And I got extra storage space in the garage in the nook where the traditional water heater was designed to go.

How often do you acid back-flush it? Most places in SoCal have hard water that quickly limes up the passages in the heat exchanger, so much so that Rinnai warranty is void in the area. Recommendation is to back-flush with white vinegar for an hour every 6 months to keep water passages clean enough to continue to work. You have to take it off-line, connect a pump to a 5 gallon bucket of vinegar and circulate it through the tankless unit's internal lines for 30 to 60 minutes.

For any house that is not vacant for at least half the time, tankless is of no advantage.

 

[WATTS-UP]

20+ years ago I installed a Themomax solar collector, I get 160 gallons of hot water per day and my girls can blow through that in a day. The cost to run the system, a few pennies, I have to pay to run two Groundfos circulators. My system consists of the following: a solar collector giving me 160 gal of free hot water, that goes into my tankless before going on to the shower etc. Oh, the system paid for itself many years ago, so now it's just about free.

The tankless doesn't even start up in the summer and when it does it may bring the temp up from 95 to 105. In the winter I turn off the tankless and run the water through my boiler, I have to heat the house so the boiler does the lifting if I need to add heat to the shower water.

I would never buy an electric tankless heater. Heat pumps are only efficient if the air temp is 45 deg. or greater.