The operating costs will be the same. Why not tankless? Cheaper with lower operating costs.

No tankless for reasons I don't want to get into here. I've done the analysis and decided against tankless.

What happens when you compare the GSP-150 (34 gal) to the GTP-150 (50 gal)? Their specs are the same. What would be the reason to go with the larger, more expensive 50 gallon?

Or GSP-150 vs GTP-130? In this comparison the 34 gallon has higher specs than the 50 gallon. Why would you ever buy a 50 gallon version?

If you just look at the specs there is a lot of overlap between the two sizes which makes this very confusing.

I am curious what ypur analysis has shown you?

Trying not to sound condescending and maybe I am missing something bit the advantage of a larger tank is that there is more water at your disposable. Yes they recover at the same rate but one has more hot water. The bigger tank will have more standby losses of course but you are less likely to run out of hot water.

With such a high first hour rating, aren't these things replenishing about as fast as you can use them? So is there a benefit to having 50 vs 34 gallons?

Let me give you a real use case scenario here. I have a tub that holds 120 gallons. Which one of these will let me fill it up without interruption?

Tub specs recommend having a 75 or 80 gallon water heater but that's with a conventional water heater. I was only considering the larger water heaters until I saw the first hour rating on these things.

Maybe I'm putting too much stock on the first hour rating?

Tankless acquisition and install costs are 2-3x the cost of a 50 gal gas water heater with parts and pieces. If there are 2 or more living in the house, 50 gallon. I might take you the life of the heater to recover operating savings with a tankless, depending on local energy and water rates. I would love to see real modeling with teenaged shower takers coupled with an unlimited hot water source....

With that being said, I still install 100% tankless in new customs (with integral recircs) while I patiently live with my gas tanked unit & $30 monthly gas bill (WH only with 3.5 users).

I don't want this thread to get into a debate of tank vs tankless heaters. Can anyone comment on the suitability of the above 34/50 gallon tank water heaters for a 120 gallon tub?

Their first hour rating is very impressive but I don't know if that is continuous or if, in the process of filling the tub, I'll be exhausting the tank and have to wait for it to refill several times.

No for the 120 gallon tub.... dimensions? The largest tub I've used 50 gal tanked water heaters are 60x42 aka a 5' oval which are 50-64 gallons less body displacement in the tub. Larger tubs I've used 75 gallon water heaters. It worked because the hot is mixed with cold. 120 gallons? That's a lot of tub & recovery delays mean the water is cooling while you wait for more hot. Time to consult a plumber or WH manufacturer. My experience is based on customer feedback (or lack of complaints!).

I think you are generalizing rather than taking the specs into account.

I don't have the dimensions handy but it's a giant two-person tub. It has built in heaters to keep the water hot because there is no way that much water is going to stay hot for long even if you could instantly fill the tub with hot water.

Like I said, Jacuzzi recommends a 75 gallon water heater, which is what I was shopping for when I came across these smaller tanks with very impressive specs.

I'm going to call the water heater manufacturer. I'm not sure what use 179 gallon first hour rating (on their lowest rated heater) is if the tank can't keep up with you. And their top of the line 50 gallon heater has 253 gallon per hour recovery which means it can produce around 300 gallons in the first hour. This is more than a traditional 75 gallon tank can produce in the first which is around 100 gallons.

First hour rating is useless for filling oversize tubs. The 6-10 minute rating would be more relevant. The manufacturer will rightfully advise you on a system with more capacity.

If operating costs are important, why not consider a heat pump water heater? The Stiebel Eltron Accelera 300 (80G) will better meet your tub needs, cost less upfront and cost less to operate than your current considerations. It will also contribute to indoor air quality opposed to endangering it.

Indoor air quality aside, gas infrastructure is increasingly a poor investment for new, efficient construction.

120g is asking a lot for a 75-80g tank but could work with a high thermostat setting, mild incoming water temperatures of SoCal and baths that are not "very hot". To be safe, most professionals would probably try to get you into a bigger tank or use two tanks.

I was originally considering a heat pump water heater but I don't have a 220 near the tank and running one to the water heater is a big expense. And I don't think a heat pump water heater would be cheaper to operate than a gas water heater, at least not here in Southern CA where the electric bill is more than all the other monthly bills combined.

As it is, whether I get a condensing water heater or a heat pump, there is an added cost for installing a condensate drain which in my case is also going to be expensive.

If a 50 gallon condensing water heater won't do the trick I'm not sure what other options I have. The only companies that I know of who make larger condensing water heaters are HTP and American Water Heaters. A cursory Google search of reviews suggests that I should stay far far far away from either company's products. Are there other companies that make larger condensing water heaters?

When upgrading I always like to get the best available products and on paper heat pump and condensing water heaters seem to be superior. But I'm on the verge of scrapping both and just getting a traditional gas tank water heater because that's plug-and-play for me. I'm running out of bandwidth to think about all this stuff.

You should really discuss with a plumbing contractor as well as the mfg. Those high recovery water heaters you're listing are many times more expensive vs a traditional tank, which is why I've not seen them. Since you're in CA, you'll need to permit and adjust your energy calculations to accommodate. The quick and cheapest way to more hot water is a 75 gallon tank. Likely the existing gas line works but the flu might have to be enlarged. It is probably cheaper to run 220 anywhere vs increasing a gas line size.

You kinda identified one of the issues. Not a lot of people have experience with heat pump or condensing water heaters. So I gotta put my plumber hat on and educate myself. In the process of building this house I have had to learn a lot of things that I don't need cluttering my brain. But that's the best way to make sure you're making the best decisions and make sure things are getting done right.

I know the quickest and cheapest way is a 75 gallon tank. But I'm willing to pay more up front for a superior product and experience. I give myself a lot of headaches wanting exotic products that contractors aren't familiar with.

Even a 75 isn’t going to do it for a heated swimming pool. 2 50 gallons for that tub. Or a tankless. Tankless would be better for the long term since the tub won’t be used frequently. It minimizes daily operating costs and can instantly ramp up to the demand of 2 of those tubs if needed. Yes, it has more expensive up front costs. But not more expensive than adding a second water heater to a home that doesn’t have the infrastructure for it. In CA, it can be located on the exterior and is about the size of a suitcase. It frees up space in your utility area. Especially since you’d need 2 50’s.

Sophie - For whatever reason Jacuzzi specifically advises against a tankless for this tub, I mentioned this above. And I prefer not to go tankless for a variety of reasons.

Springtime - The specs for this water heater show that the first hour delivery is a paltry 76 gallons and it requires a 240. My knowledge of electric infrastructure is minimal. I have a 110 by where the water heater goes. Are you saying I can supply 240 to this without adding an outlet? My central vacuum uses this outlet and it needs 110 so I can't totally turn this to 240.

But the bigger issue is the first hour delivery. This thing seems wimpy. They don't specify the recovery but they say "A heat pump water heater’s recovery time is slower than a standard tank." How is this my best option for filling a 100+ gallon tub? To my limited knowledge this seems like the least suitable water heater. What am I missing?

The gas venting is already there because the existing water heater is gas so no duct work is needed. The issue with the condensate line is that it is acidic and in my situation providing a suitable disposal area is a going to be a big headache. Doable, but not easy or inexpensive.

Remember the tank stores at 120+ (my HPHWH is set at 126) and you bathe typically around 100. If your groundwater is 60 - probably right for SoCal, and you raise the tank to 140, then you have effectively 150 gallons.

Recovery will be better based on ambient temp and ground water temp. So you see why they are favored in cooling dominated climates? Not to mention, they cool the area they are in when they heat the water.

But they are noisy and gas is cheap. Best suited for SE US where electricity is cheap.

I think Heat Pump Water Heaters are best suited for ALL new construction concerned with efficiency. High performance homebuilders are using them in all US climate zones and the highest priced electricity markets. If building new and can accommodate their space requirements, they are a better choice than gas almost every time in every region. For basements or tall crawlspaces, they are perfect replacements as they reduce dehumidification needs.

Having personally handled the Accelera 300, I can assure you it's not wimpy. Its size and weight are a disadvantage for installers. As for noise, it's quieter than my 90s model fridge, and uses the same technology for those still unsure about that.

Again, first hour rating has nothing to do with filling tubs. The ratings of those condensing gas units are impressive, but an 80g tank has much more capacity for hot water immediately available so it will give you better performance overall. The Accelera 300 first hour rating is listed at 74g which is similar to most like-size gas and electric tanks. This is an amazing feat considering its energy factor of 3.39 is the highest energy star rating of any available water heater.

A typical 14g wire can be configured for 220/240 volt, but it needs to be dedicated. HPWH condensate is not acidic compared to gas heater condensate.

Electric utilities are starting to offer very appealing incentives to use electric tank water heaters as batteries. With these incentives or using the tank to take advantage of time-of-use billing, one can expect even more savings compared to gas. For these and other reasons, I would choose a Rheem Marathon (hardy, electric tank) before any gas model, especially tankless.

What about a 70-80 gallon condensing water heater vs the Accelera 300? Isn't the condensing heater better on paper?

Problem
is there aren't many to choose from. HTP and American Water Heaters make them but they are very poorly rated. AO Smith makes this one but it's technically a commercial unit, whatever that means. Does anyone know of other options?

Point of clarification to the last post, I think you meant to say "HPWH condensate is not acidic compared to condensing gas heater condensate." A regular gas tank water heater does not produce acidic condensate.

The tub does not care how the hot water it uses is produced. Just that there is enough of it. It’s either go double regular tanked, go single GIANT tanked to match the tub, or go tankless. Tankless will suit your overall usage pattern much better. And use less energy.

Other than tub, tankless having usage pattern or performance advantages is debatable and I think HPWH use less energy than tankless. The energy that HPWH uses is cleaner too.

I think Accelera 300 could work for your tub but not sure. It depends on thermostat setting, incoming water temp, number of gallons and desired tub water temp. A point of use electric heater could give an extra boost if needed. 110 gallons would probably be fine without it. 125.. depends.

From what I've seen, not much compares to an Accelera 300, especially not expensive gas water heaters, condensing or tankless. And regular atmospheric vented gas water heaters should be illegal as they are such reliable backdrafters. If you want AO smith brand, we have used their HPWH and the engineer homeowner loves it. They are pretty well reviewed too.

I am not going tankless.

I am sure the Accelera 300 will work because a 75 gallon tank is large enough for my tub. My original question here was if the 50 gallon AO Smith with amazing specs would suffice but it will not. Any 75 gallon tank will work but now the decision is whether to get a traditional gas tank heater or condensing tank.

When you say not much compares to the Accelera 300, what are you referring to? The AO Smith run circles around it with respect to first hour and recovery. Are you referring to operating cost? On paper it seems like it's hard to beat a condensing water heater. Please help me understand.

I'm really at the point of throwing in the towel on all these fancy new water heater technologies and going the traditional route. Condensing heaters are way more expensive and in my case I'll have to bring a 240 over plus the expense of dealing with condensate. I don't think the math works in my favor.

Water heaters are the 2nd biggest energy user in most homes. In really efficient homes, they are the biggest energy user. It makes sense to seek out something that's efficient and reliable.

Not much compares to Accelera 300 in terms of investment, performance and appropriateness.

Investment includes upfront costs, operating costs and reliability. What models run circles around the Accelera? Surely not the ones in your original post with half the capacity and twice the upfront costs. The Accelera 300 is more efficient than any available water heater including tankless and it's priced for a fast simple payback.

The Accelera 300 can serve 5 possibly 6 people. Why ignore upfront costs and long term energy savings for better recovery? It's probably very rare needing better performance than an 80 gallon tank with a 74 first hour rating. For better performance, tank capacity is typically more important than recovery ratings.

I think all gas water heaters are usually inappropriate in terms of the damage they do to society, environment and added risk to a home's indoor air quality. This is in contrast to a HPWH that reduces space conditioning costs and mitigates interior water vapor problems.

Please do not choose a natural or atmospherically vented gas water heater.

Are you sure you can't repurpose a 15amp circuit? The existing water heater power supply is on a shared circuit? What about that existing gas venting infrastructure? Age? Inspected? Safe?

I have a 110 by the water heater but I need that as 110 for my central vac and the recirculating pump. So the only way is to bring a new 240 line.

This is the water heater I think outperforms the Accelera 300: https://s3.amazonaws.com/s3.supplyhouse.com/product_files/AO%2520Smith-BTXL-100-Product-Overview.pdf

It's a 75 gallon condensing water heater with much better specs. But it's more expensive, requires a condensate line and porobably a 240 (I don't recall). If I'm going to go through all that I might as well get the tank with the best possible specs. How is the Accelera better than this one?

I'm really at a point where the natural gas tank heater just makes the most economic sense. I am very conscientious about my environmental footprint but there are limits to what one can practically do. I live a very eco friendly life and have done other things to be green, if I end up with a gas powered heater it is what it is.

Link didn't work but any other heater is unlikely to outperform Accelera 300 in terms of economic investment. The Accelera 300 will be more affordable up front and over time. Extra recovery performance will be expensive and rarely needed.

In general, heat pump water heaters are better economic investments than anything gas.

usc - from an economic standpoint, you are probably right that a condensing hot water heater does not make sense. It depends on what your hot water use is and it sounds like it is very little. How much do you pay for gas and do you know what your typical hot water portion per month is? And then what do you pay for electricity?

I just spent 4 months in a townhome where we had a tankless hot water and the only other gas appliance was the range. Our bill was $4 a month (over the base charge) because we used between 4 and 5 therms a month. So I know that $50 is a my rough annual usage in this situation. It was fall/winter so incoming water was at its coldest. That would be the standby losses with a tanked unit although the condensing would be much less.

I went back and forth with the idea of a HPWH and was discouraged by the poor reliability issues. But I would do it in a second if I could convince my wife to give up gas cooking.

Financially - don't change a thing sounds like the best option. Environmentally - HPHW. Condensing doesn't make much sense unless you use a lot of hot water - and you don't.

We have two 50 gallon water heaters that have some automation. During the weekdays I have 100 gallons of water ready at 6:30am (there are four morning showers), one water heater cuts off at 8:00am and doesn't come on again until the next week day. The other water heater stays on, although the temperature does adjust to lower temperatures at various times of the day.

The controls cost me $150 total and I am using them on two regular water heaters, my gas bill went down quite a bit by adding the dynamic temperature controller and a second water heater. Rethinking the way you use and need hot water and adjusting your water heater accordingly will save you much more money than paying a bunch of extra money for a more efficient water heater. My water bills are low enough that the additional money required for a more efficient system would never even approach paying itself back over its lifetime.

50$ just for gas in a townhome? My single family runs 50$ electric. No gas bill.

Accurate accounting for gas costs should include utility provider minimum fee. For single appliances, you can divide by # of appliances, just know that better alternatives exists for all gas appliances, all things considered. Zero for gas is easy.

If reliability is most important, then choose a Rheem Marathon electric tank. It makes me cringe to think how long these will last, but when used with the electric utility in a sharing agreement they are transformed from an energy liability to asset. Depending on the situation, this could be a better investment than HPWH.

Tanks get a bad rap but standby losses evaporate with good air-sealing and insulation, just like a house.

I installed a Marathon ten years ago and love it. Related problem is I can watch my electric bill climb on months that I run my basement dehumidifier. If I had waited for the HPWH, I could have made both costs go down.

The Stiebel Eltron (Accelera) and AO smith HPWH have very high reliability reviews. For the Accelera, I expect better reliability than any gas appliance comparison. Gas carries extra maintenance concerns.

Not only do condensing water heaters not make economic sense, neither do cheap residential gas water heaters. Tell us the cost of the water heater, kwh costs, therm cost, monthly service fee and Energy Factor EF or use that link to help do the math for your situation. Most HPWH have EF ~ 2. The Accelera is 3.39.

All this is without adding in new construction gas infrastructure which can be surprisingly expensive.

Good golly there's a lot of bad info in this thread!

Springtime Builders: What are you even talking about with the Accelera 300?!? It would be a terrible fit!

So uscpsycho: The first thing you need to understand clearly is that you are talking an EXCEPTIONAL amount of hot water. It's really stupid wasteful.

To answer the original question though would require that we know what your inlet water temps are on a cold day.

Let's make a few assumptions: Let's assume a water temp of 115 (we normally design around 105, but you will have some cooling of the water as it is filling so start with 115F.

Then let us also assume an inlet water temp of 50F. (I'm pulling that out of my rear... but is a good starting number).

The 199 btu per hour input will provide about 5.7 gpm continuous at 67 F temp rise. You would be able to fill your tub at that rate (5.7 gpm). So assume you get 50 gal of 115F water from your water heater (that is set at 125F) the rest of the fill will only be able to go at 5.7 gpm. Note: a standard tub fills at 4 gpm... I'm assuming you have larger water supply to this kind of tub.

The minimum you will need is the 199k btu unit.

Note: All of the issues of gas service that apply to gas thankless apply to this as well. This is basically a large tankless heater strapped to a 50 gal tank.

Springtime Builders : I agree that hybrid electric water heaters are less expensive to run than gas tankless (not by much). They do require a basement, garage, or similar space in which to pull air (heat). The ones without a significant backup resistance heater are going to have very slow recovery.

Unless you are getting significant solar or hydro electric feeding into your grid, the electric vs gas pollution is nonsense. Electric is provided primarily by coal, natural gas and oil.

Gas tankless is an excellent choice if continuous hot water is an issue. Hybrid electric doesn't come close on that.

I like hybrid electric water heaters. They are cost effective to install and operate as long as reliability is not an issue. If someone needs fast recovery / large volumes of water gas tankless ( or hybrid tank) is the way to go.

An 80g tank that can replenish itself in one hour should handle 90% of 4-5 member families. Bigger tanks negate needing to have tanks for your tankless.

I don't think promoting the two best water heating investments I know of is a terrible fit for any home. Yes, HPWHs take special space requirements. Get smart and figure out if possible. For new construction, temperate garages, basements and tall crawls, they make a lot of sense.

All the Accelera needs is a 14g wire and drain. What does a gas heater need?

Significant amounts of solar and wind are being fed into the electric grid. So much that electric companies are paying homeowners to store excess in tank water heaters! Now those of us without turbines of solar panels can participate in cleaning the grid with some easy water heater decisions.

Unfortunately, nothing about gas works this way. On top of that, people still seem to think that gas is the cheapest way to heat. For typical residential needs, it's not.

The OP was asking for a heater to fill a 120 gal tub. The Accelera 300 will not reasonably do that. It will provide about 75 gal in the first hour - it then requires almost 10 hours to recover. It claims 147 gal of 104F water - but that sounds iffy based on a tank temp of 150 - which doesn't sound reasonable without a boost from the electric resistance heat.

I like a large tank tied to a heat pump. The trade-off with the the low current requirements is the slow recovery because it can't use much of a resistance heating element.

I noticed that the Accelera 300 was ~ $2500 which is twice the cost of the top of the line Rheem tankless I've installed on my two houses. You have a point that the tankless gas require venting, gas service, electric outlet and condensate drain. However, much of that is already in place for other reasons (drain for the pan / TP valve, electrical for other things such as water softener, etc.)

Note: you make a point about not having gas service at all. I think that could work in the south where this kind of water heater would also work well. Here in the midwest, gas is commonly used for heating also.

I think the Accelera 300 is an interesting entry and I like it... but it's going to be very slow recovery if you have large water use. The large up-front costs is tough also.

A more standard hybrid heat pump like the 50 gal Rheem for $1200 is probably going to work for more people at a reasonable cost upfront. It has larger resistance backup coils for faster recovery if needed.

Me and the OP seem to think they will squeeze by with 75g in their climate as long as the big drain is at night, I don't see a problem with recovery.

I found the Rheem suggestion, I think this new prestige model. Amazing specs and price. I would go for the biggest capacity possible for better performance. I worry about touchscreen electronics and reliability compared to Accelera but at that price and efficiency, seems like an incredible bargain. Thanks for sharing!

Good luck making an economical gas comparison against this new HPWH.

The difference in annual costs using the DOE energy tag between the Accelera 300 and the Rheem condensing tankless is $43 a year. The installed cost is about the same unless you need to run new gas service or upgraded gas service just for the water heater.

That's pretty close.

The tankless is smaller, doesn't require air exchange and provides continuous hot water.

The Accelera 300 provides some cooling / dehumidification but is very slow to recover.

The condensing gas tank heaters are mostly niche market - I don't see many people using them but would be very appropriate in the OP's situation. He will be very disappointed if he actually tries to use the Accelera 300 to fill his 120 gal tub.

It is close. Closer to $60 savings with Rheem HPWH not including monthly gas service fees. Why have another utility provider charging more than electric provider when appliance costs are similar (Rheem)? Do people enjoy adding indoor-air, fire, explosion risk and infrastructure costs just for promises of unlimited hot water? All-electricity is cheaper, safer and performs close to the same.

Big tanks mute recovery. You have to add tanks to tankless to make them perform as well as a tank. Might as well buy a bigger tank. Save money and maintenance. Not what suppliers, builders and plumbing contractors want you to know but true.

I'm confused why the 147g at 104 rating is not enough to suppress concerns with filling the tub? As for recovery, guess my "as long as its at night" solution might lead to some disappointment. I'm just glad that 125g is atypical. Hope to do a woodstove/compost hot tub some day. Did I mention I really like cheap hot water?

Oh for heaven's sake, what is the matter with you!??

Nobody is installing another utility just for hot water. Get your head out of your rear end. The rest of that nonsense is just FUD.

If you don't live in the south or a moderate climate on the coast, you are installing gas because it's the cheapest way to heat your house.

The difference is $43 a year comparing similar size units: the 200k Rheem tankless and the Accelera 300.

You reasonably get about 98 gal of 105F hot water out of the Accelera 300 based on 125F tank temp and 60F inlet temp. That's good... but if you ever run that out you have a very long wait. A 10 hour full recovery is a big deal that shouldn't be dismissed. In the situation where the OP is filling a large tub, you would have to design around higher than 105 - that 's why I was saying 110-115 F. Again, if the OP can even fill his tub, he has a 10 hour wait for a full tank of hot water again.

I've been recommending the Rheem hybrid electric for a couple of years. The first round of hybrid electric were iffy in terms of reliability and one repair call would negate any savings - but the newer ones seem to have it figured out. Even so, they won't work in a lot of situations where there are problems getting the air circulation.

I'm sorry but what is nonsense and what is FUD? We agree gas is not the cheapest way to heat water but you think physics are different for air?

Unless a home design is oversize or inefficient, gas is not necessarily cheaper. People are building affordable zero-energy homes with no gas in very cold climates. Heat pumps are getting crazy good. Many reasons why the industry might try to ignore these developments.

As long as the tank fills oversize tub at night, recovery is not a big deal. Why would you need a fully recovered tank so fast? Plan on filling another ridiculously oversized tub so soon? Even if tub is filled during day, a partially recovered big tank is going to handle most tasks. Recovery is the most overrated concept in this thread though it's good to point out it could be an issue for a big family that often fills 125g tubs.

Springtime - $50 was the annual bill ($4 a month) for the townhouse (posted accidently under my wife's name - jln333). Also you should acknowledge that physics is indeed different for air. You heat water at every outdoor temp but heat air when outdoor temp is on average much colder. You know that and ignoring it just opens you up to a strong counter argument. Also, while heating a tanked electric hot water heater is good for storing extra electricity, 99.9% of people don't have that option today. I think that is not a good selling point. I get that you are passionate about gas - stick to the better arguments. The OP is not building new and uses NG already most likely for several things.

Jake - you mention generating electricity with oil. Makes you look pretty ignorant in all things energy and environment related. Springtime is right that electricity is cleaner in many areas and is getting cleaner every year. Gas is sometimes the cheapest way to heat and sometimes not. That depends more on local costs than local climate. And gas gets dirtier every year.

OP is in SoCal. Average water inlet temp is 72-75 degrees.

David Cary True, I hadn't looked up the sources of electrical generation in US recently -- but the point still stands. Most of electrical power is coming from fossil fuels still 63% ,with nuclear providing 20% and renewable s 17%. Depending on where you put nuclear, electricity is still pretty dirty stuff. In the midwest where I live it's really dirty because much of it comes from coal. Other than renewables (only 17%), how would gas ever be dirtier than electricity?

When you are talking costs, it is both climate and local energy costs. In colder environments heat pumps have traditionally not been a good solution. That may have changed recently as tighter construction and better heat pumps change the equation. Heat pumps in my area didn't hold up, they were on resistance heat too much and customers didn't like the "cold" air from the registers.

And yes, I do know that there is a big difference in air-air heat pumps for heating water where the ambient temps don't get below 50 degrees or so and outdoor air temps that get -15F. The same physics do apply to both.

I have been pushing energy conservation for a long time. It's great that all of these technologies are becoming more refined and mainstream. I'm glad to hear about new products that make incremental improvements that eventually allow us to re-think what we are doing. Condensing gas appliances, heat pump water heaters, ECM motors, PV solar, it's all good stuff and getting better.

That said, from a plumbing standpoint I don't live in a world of new construction, zero energy, So Ca. When it comes to a water heater, saving $43 a year isn't probably an overriding consideration. Mostly what I see is existing construction that may or may not have gas already (usually does). Things like having the physical space, having an air heat sink, venting, recovery speed, and installed costs are going to dictate the type of heater that's installed. Truth be told, even getting people to install the $1,200 version of a hybrid electric is a stretch a lot of times.

David and others, the future is now. Duke Progress, among country's biggest, offers water heater sharing in EnergyWise program. Aren't you a Duke customer David? In CA: PG&E, SDG&E and SCE are listed as having Automated Demand Response programs. Not all customers qualify but having a tank electric water heater is a must. Among the best ways to help the grid and it's widely available. I think it's a very good argument, especially because it's so affordable.

HPWH qualify as electric storage water heaters and can usually be wired for sharing but even a regular electric tank is better for society than gas when used in this way. With the durability of a Rheem Marathon and utility incentive/sharing, potentially cheaper than efficient tankless NG over long haul.

I might have worded the physics thing differently, but my point remains. Heat pumps are available that draw heat from -17 degree air. For efficient residential, it makes more sense to use heat pumps than gas. Any existing replacement should be skeptical about upgrading infrastructure or continuing gas appliance use in a space that would be well served by dehumidification. Replacing existing natural vented gas heater with another naturally vented model is never a good idea.

I missed the $50 a year but feel this is very misleading to other readers. Most households with efficient tankless NG will be closer to $200 (LP gas higher), which might not include monthly service fees. In that situation, using induction and HPWH could have been cheaper up front and eliminated the total yearly gas bill.

17% renewable for electricity is cleaner than 0% renewable for gas. Renewables are growing so fast that excess generation is a major problem, hence why electric tank water heaters are better. They can play a big part in a more renewable grid.

It takes persistence and passion to help those who grew up with gas realize that it's not the best way to heat. Not only has it become more expensive in most markets, gas combustion is a cause for serious health concerns in efficient homes.

CA - 1.817 per therm for Tier 2 PGE (above the first 0.46/day) & of course with my outdated gas tank & 4 shower/day we exceeded tier 1. My personal home had a fairly new high efficiency heat pump HVAC system when I bought it (60yo "project" home) while 100% of my builds have been natural gas heat with integral recirc tankless water heaters. My personal homes become the building lab so it may go ele.

Brian, I'm definitely seeing things differently this year with a client coupling solar & pool heat pumps. I pitched heat pump to these people but they weren't ready.

Next client is asking about hydronic floors. The last one I installed was gas. This one? We will see.

In CA our energy rates include large tax loads as well as the cost of rebates handed out to others.

Springtime Builders Dude.... breathe into a paper bag, you are hyperventilating.
You are way ahead of the curve.

30% coal, 30% natural gas, 20% nuclear doesn't ever = cleaner than natural gas - even if you put nuclear in the "clean" category. Neither has it become more expensive in most markets. The reason that gas is replacing coal is because it's cheap (and less polluting). Nuclear has it's own issues and renewables are great, but storage is a serious problem for grid stability. A cloud system moving across the region causes transmission companies to scramble to maintain stability. Until the storage issue is solved, PV solar will be limited as a percent of the total. Here, and in much of the country, the energy management system is about limiting peak demand- not storing. They are shutting off air conditioners and electric water heaters during the day.

The part about "it's a cause of serious health concerns for efficient homes" is more FUD. Efficient gas appliances have been using outside air intake for a while. The only appliance that doesn't is a gas range. If the house is so tight that a gas range is a concern, then there are probably other indoor air quality concerns that need to be addressed with air exchange.

"Most households with an efficient tankless appliance are going to be closer to $200". You don't get to make this stuff up. We are using DOE energy stickers so that we have a valid comparison.

"Replacing an existing naturally vented gas heater with another naturally vented model is never a good idea." Again, you are out there... so looking at a 40 gal gas standard, cheap water heater has an estimated cost of $208 a year and a purchase price of ~$400. That, vs. $155 a year and a purchase price of $2600 for the Ecellera 300. If this is a replacement (gas and vent is in place) the standard gas tank water heater makes a ton of sense for most people. If they have to finance the more expensive option, the cheaper option makes even more sense. What really sucks in my area (besides propane) is electric resistance heat (space heating or hot water).

Look, I get it that you are pushing this idea of using electricity only in new construction and avoiding the base use charge for natural gas ($9 a month in my area). I also understand that PV has good potential as a renewable. But don't exaggerate your claims, don't assume that most of the country is like So Ca. and don't assume new construction. Also don't assume that there aren't capital costs that prevent many low-middle income folks from participating at all.

I'm going to throw another wrench in all this by saying that having gas as an option has probably kept a check on electrical rates - again in my area.

Springtime - Duke offers $25 a year but that is only for a/c shutdown. It varies by region of course.

I used the $50 a year as an example of a efficiency minded household and the use of hot water (I think the OP said he was not using much). I think the DOE numbers are crap and need updating. But I agree that $50 could be misleading. We also just got a water bill for 1000 gallons for a household of 3. I was kind of surprised by that. Estimates vary but 6,000 would be average. We don't do anything too crazy - front loader washing, bosch dishwasher, dual flush toilets.

WonderJackDog, this forum is building a home. I try framing my advice for the widest possible audience. So far you have accused me of terrible advice, having my head up my butt and hyperventilating. I'm actually really happy on my end and very much appreciate your contribution of the Rheem HPWH option :)

Its hard to take you seriously on the energy stuff with apparent total miss on using tank water heaters to help with the renewable storage problem. Sounds like thoughts on tight homes, natural draft heaters and ventilation are equally troubling.

As for the health concerns, (sorry OP) let's go there. Way to go wonderdog.

Fact: Homes without attached garages or combustion appliances don't need CO detectors.

CO detection is an added cost and especially worrisome maintenance concern. Detectors do a poor job, have short lives and zero maintenance is common.

Combustion inside the living space is an often overlooked health and life-safety issue. Even for the newest, best gas appliances with "outside" combustion air. This is why code requires make-up air for kitchen vent hoods over 400 CFM. Not just for tight homes but all homes.

A recent client insisted on tankless NG, a supposed sealed system using outside combustion air. When the oversize vent hood runs, the tankless water heater automatically shuts down when someone tries to shower. Not by choice, it's a safety feature built in by tankless manufacturer. It's a "good" thing but shows they are not completely airtight. I think my rater said most leak at 50 pascals.

I don't worry about homeowners deserved hassle of coordinating usage lifestyle, I worry about when that safety feature eventually breaks down and the tankless water heater runs at the same time as the vent hood. This will likely suck combustion exhaust from the "sealed" tankless gas heater into the house.

Even if the combustion exhaust has no detectable CO, water vapor is still considered a pollutant while the HPWH eliminates CO and reduces water vapor.

I'm not as worried about death as low level CO exposure over time. It seems a silly added health risk when better, more affordable options exist.

Financially, this is not a complicated decision. Each $100 you spend up-front needs to return $14.25 in annual savings, assuming a 10 year investment life (which is about the longest you should go in any home upgrade). So a $1,500 investment needs to save $214 annually. Longevity of the appliance really doesn't matter that much once you are past 10 years (at least financially).

If you want to adjust the above amount for reasonable inflation each $100 spent up-front only needs to return $12.25 in the first year assuming a 10 year life and a 2.5% annual inflation rate.

There are other legitimate reasons for going more fuel efficient, but those are not financial and so I am not addressing them.

Where exactly does 14.25% come from? Arguably for home improvements it should be dependent on your likelihood of moving and whether your market values such things. I used a 50 year payback but I recognize that isn't financial. But having a tight house has value well beyond dollars. A tank of hot water - not so much. Some value but not much.

First, payback period is garbage, never use payback period for any decision and stop people who attempt to talk to you about payback periods. Conservatively, the doubling time of money is 12-15 years, I actually 9 years for my personal financial decisions.

Next, I used a present value calculator to get $14.25, however, it isn't really necessary. Just ask yourself would you rather receive a thousand dollar bonus on your next check or $142.50 once per year for ten years. Money in ten years simply isn't as valuable as money today. For myself, a dollar in ten years is worth about 40 cents today, when I am advising people I tell them to use at least 60 cents.

Never do a home improvement based solely on what the market values. Very few people can find arbitrage in home improvements, especially considering transaction costs.

David and bry911: I appreciate the discussion on investment decisions (payback and net present value). As bry911 said, there are some reasons, like not being held hostage to energy prices, not contributing to over-consumption, not contributing as much to environmental damage, etc.

All of that said, there's an issue where the cost of housing has completely outstripped the ability for many people to afford it already. Even with "Energy Efficient Loans" much of this is getting out of the reach of even the middle class.

I know this conversation has gone far- afield. But I couldn't help but come back to the OP wanting to fill a 125 gal tub and Jeffery talking about his clients wanting to heat their pool with a heat pump. Those aren't "first world problems" those are "top 10% of first world problems." There is value to some of these folks creating a market for new technology thereby making it cheaper and more reliable, but pushing it downstream is important also.

Part of my reaction to Springtime Builder is that in all of his passion, he's tone deaf to the way that the vast majority of actually people live. Nobody I know is doing a NPV calc when their water heater goes out. Ever. Most are saying, "oh crap... an $800 replacement (standard gas or electric resistance tank + install) means we are going to be in financial trouble for a few months or more."

199k btu requirement for the condensing gas waterheaters will require a large gas line up size from the meter to the water heater just as it would for a tankless and potentially some changes from the local gas provider service line and meter.

Nobody I know is doing a NPV calc when their water heater goes out.

But they do, they might not throw it in a calculator but we all do a cost benefit analysis when asked to spend money, and often we err on the side of deferral even when paying the money makes more financial sense.

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The problem when discussing energy efficiency is that it is largely a profit vehicle for companies. People who rank environmental issues highly are likely to spend more money on a perceived efficiency benefit. This creates a market for selling energy efficient everything to people at a terrific mark-up, which in turn drives a marketing war of green appliances and techniques.

In reality changing the way we use energy is far better and more impactful than installing greener appliances throughout our house. Aside from that put your money in the things that will do the most good. Or forget the energy efficient home altogether and just become a vegan, and make history by being the first vegan not to constantly tell everyone about it.

Funny, most vegans I meet are secretive and don't like talking about it. Probably result of shocked reactions (guilty as charged) and related bullying.

I can see why a financial analyst might try to use NPV for this but it adds assumptions other than regular investor meeting or beating market. Comparing a tankless gas heater to a large tank heat pump water heater with different fuels and performance details is not that simple. Who cares about negative NPV with tankless lag and cold water sandwiches or HPWH making an important area less comfortable. Is positive NPV more important than possibly poisoning your family with cheap gas tank combustion exhaust?

Sure money is more valuable in the future including appliance cost and replacement labor. Hassle of emergency replacement is part of reason cheapo heaters exist. Better planning includes durability, especially when health is at risk. A 6 year life for a gas tank is more unsafe than 6 year life for electric tank.

I'm guessing Bry's bean counting didn't include infrastructure or monthly utility fees either. I've heard some gas fees are as high as $30 a month/$360 per year even with no gas usage. Some have low infrastructure costs, but it's not uncommon for deeply buried gas supply lines, trenching and backfill to run in the thousands for our area, mainly for challenging lots. Our HVAC contractor charges a per appliance drop charge fee for gas supply pipe in the house, roughly half the cost of the cheapest water heater. Don't forget venting!

It's not just about energy efficiency, paybacks and investment. This decision involves health and life-safety. Bry's water heaters and wonderdog's most economical suggestion are atmospherically vented gas heaters. These are dangerous appliances because they backdraft combustion exhaust regularly:

Picture from above link 3 problems with atmospherically vented appliances.

They are most dangerous inside a home. Garage installations are certainly more acceptable but they are still unsafe. Most attached garage-to-home interfaces are not airtight. Prevailing wind, stack effect, bath fans, dryers and most notably kitchen vent hoods suck garage air into the home. Having an open flame pilot light, inside the garage which is sometimes exposed to flammable fumes is not safe either. I have a friend that was tragically effected by this exact situation.

If the garage is well ventilated to the outdoors, has no living space above, does not face prevailing winds has an airtight connection to house and is not exposed to flammable liquids or fumes that makes them more acceptable but all of that is such a stretch it's safer to say never.

In case others like wonderjack have missed it, my next recommendation after a HPWH is a big, electric-resistance tank (or two smaller ones) which can be very affordable and high performance. Using electric tanks with switches, timers, Time-of-Use metering or Automated Demand Response are ways to use energy more appropriately while increasing the safety of a home.

I realize good situations for gas exist but for the most part, it's not the cheapest way to heat anymore. It doesn't make sense for most new, code-built homes or those considering upgrading infrastructure for existing appliance replacement.