If you have or design the right space, heat pump water heaters (tanks) offer the most affordable hot water, such as the Steibel Eltron Accelera or the the Rheem Prestige. I would choose the Prestige for budget builds and the Steibel for long-term ownership. Typical american five occupants may need to space out showers a bit.

For ultimate durability, a rheem marathon (electric tank) could go 30-130 years.

Gas is problematic for the indoor air quality concerns of backdrafting and as OP has encountered, high upfront infrastructure costs. Don't forget to include the minimum monthly, utility gas fee of unneeded utility hook-up.

A simple electric tank located near renewable energy input or set up for demand control power sharing with the electric provider is a better choice for the environment and society than gas. Heat pump water heaters even more so, which spit out cool, dry air instead of the fracked, fossil fuel combustion exhaust of gas.

"Gas is problematic for the indoor air quality concerns of backdrafting and as OP has encountered, high upfront infrastructure costs. Don't forget to include the minimum monthly, utility gas fee of unneeded utility hook-up." And your other comments.

You seem to not tire saying the same things that are untrue repeatedly but I know I'm not alone in tiring of reading your intentionally misleading and false comments.

Elmer J Fudd,

yeah, I'm with you on that.^^^^

Electric resistance tank heater is the worst answer all the way around. The cost to operate, worst for the environment, and totally unsuitable for a high draw situation.

A heat pump heater solves some of those issues, but is still not a great solution in high draw situations.

The heater that the builder spec'd is not a bad solution. Another poster was talking about a 75 gal, 100k btu @96% efficiency which would also be a great solution. State Model # GP6-75-YTPDT

I'm kinda blown away by homes that are 5-6000 sq ft and need a heater that size, but that's a different issue.

Springtime's approach to building very airtight and all electric -- avoiding the cost of another utility - along with the minimum billing for that utility-- makes sense within that context. But often it doesn't make sense outside of that context.

From 2014....I apologize if I already posted this https://www.houzz.com/magazine/how-to-switch-to-a-tankless-water-heater-stsetivw-vs~21634433

The electric hot water heaters are less money than an equivalent gas version. The problem is the first hour recovery for the electric tank is poor compared to the gas.

The State Model # GP6-75-YTPDT has a 100K BTU input. That is a serious tank hot water heater. It is rated for a first hour recovery of 130 gallons. You should be able to run 5 showers in parallel with this beast.

"The problem is the first hour recovery for the electric tank is poor compared to the gas."
Assuming you were talking about electric resistance water heaters:

That's true... but the other problems are they are very expensive to operate and they suck for the environment. Just for example: A 50 gal resistance water heater has an energy guide of $419 a year - vs about $200 a year for a condensing gas heater.

Even heat pump electric water heaters have very slow recovery. Checking the specs for the units boy wonder cited, it seems like about 20 gallons per hour recovery is it. 60 gallon tank - 3 hours. Such slow performance isn't likely to be acceptable for many people.

By comparison, a 60 gallon gas unit would recover in little more than an hour. An on demand gas unit has no recovery time at all, of course. But more importantly, in high rate areas, which are numerous and growing, heating water with electricity is much more expensive than with gas.

You can also save money on plumbing and water use by building an outhouse in the backyard. Everything has a cost versus convenience trade-off but this is one that isn't hard to decide on for locations where gas is available. With all electric sites, there's no choice.

thinkdesignlive, that houzz tankless link stinks. The most cited tankless research found that tankless can have 20-40 year paybacks, past the lifespan of many units. Then come tankless drawbacks of delayed delivery, cold water sandwiches, consistent supply temps, minimum flow rate for firing and performance of multiple simultaneous draws. Not surprising that tankless manufacturers are now adding small tanks to tankless to make them perform as well as a tank!

Fact: Electricity is now more affordable to heat with than gas for most of the country. For space heating, this is easily fact checked by using the high efficiency heat pump option for this home energy calculator and the2017 EIA data. For water heating, comparing Energy Factors of the heat pump water heater models I listed, gas is even less competitive.

Fact: Gas combustion appliances add risk to indoor air quality mainly through backdrafting but gas supply leaks as well. How risky is debatable but electric water heaters are always safer.

The Steibel Eltron heat pump water heater I linked to above has a first hour rating of 74G which is ~4x better than misleading statement above. It's rated at 147 gallons of water available at 104 which is a helluva lot of hot water, more than enough for most families. It's recommended for families up to 5, possibly 6.

Whether a simple electric resistance tank is less environmentally friendly than gas is debatable. It depends on many situation specific variables. Do enough research and you may come to similar conclusion that most green builders and energy efficient experts favor an all-electric approach, even in cold climates.

One doesn't need rooftop PV to make an electric tank more friendly. Renewable grid energy is growing exponentially, up 15% since 2015. Forbes reporting recently that renewables have surpassed coal. Electric tanks in regions of renewable input or enrolling in electric provider's demand control agreement is probably a more responsible choice than anything gas. Especially for new construction or renovations facing infrastructure costs, gas is increasingly a bad investment.

"Fact: Gas combustion appliances add risk to indoor air quality mainly through backdrafting but gas supply leaks as well. How risky is debatable but electric water heaters are always safer."

Yes, if you ignore facts, anything can be "debatable". Proper building technique (which I'm sure you know as a contractor) isolates gas appliances to outside the interior living space and provides both combustion air and ventilation for the installation locations. I have 2 gas water heaters and two gas furnaces in a total of three different locations in my main home (nothing in the attic or crawl space) as an example and if for some reason one of the vent stacks broke or became blocked (very unlikely) the air would exhaust to the outside. None are subject to back-drafting because of interior exhaust equipment. Am I missing something?

and

"gas supply leaks as well"

The same plumber who runs the water lines and connections also does the gas lines and connections. Are you saying one leaks and the other doesn't? Do you avoid putting water pipes into your building projects? Yeah, more BS.

Isolating gas appliances in smaller rooms increases backdrafting risks as pointed out in this Canadian Backdrafting Resource under heading Avoid Conditions That Lead to Backdrafting.

Obviously any home with running water risks leaking water pipes. Homes that have gas supply pipes risk leaking gas too. I think it's safe to assume gas lines leak as much as water lines but leaks are much harder to detect.

Combustion exhaust is the main gas appliance leak to be aware of but supply pipes leak too as evidenced in this recent houzz thread. I recently heard of a hair salon held liable for health problems of employees and clients from a leaking gas supply line to a water heater.

All-electric homes have zero risk of indoor gas supply leaks or combustion exhaust pollution. Now that's a fact!

I think some or even most heat pump hot water heaters have back-up electric resistance to speed recovery. Obviously that negates the energy savings and is likely still slower than gas, but would still mean running out of hot water less frequently.

Please stop spreading out misinformation. Everything could be built improperly. But I am pretty sure it would be next to impossible for POWER VENTED sealed appliance to backdraft. Modern on demand water heaters and furnaces detect these conditions.

Springtime Builders,

You are a bright guy, so you should understand when your ego is causing you to overstate your case. You are losing credibility fast with every post.

Your practice of building all-electric, avoiding the cost of installing another utility and the facility charge that comes with that is very reasonable. So is the use of heat pumps - as well as positioning a house for a future with an energy grid that's powered by fully renewable energy.

But when you use scare tactics, and various other misstatements, you start sounding like a crank rather than a reasonable person.

We are comparing sealed combustion gas appliances. Back-draft isn't an issue. I can tell you that a hundred times more people have been killed in residences from fires with electrical origin, than ever killed by a gas leak - and that would be true, but about as misleading as the information you are giving.

I've already done the math and shown you why electric resistance water heater is worse for the environment than a 90+ efficient gas appliance until the grid is at least 50% non-carbon powered. Despite the growth in renewables, that can't happen until utility scale storage is a thing.

I take issue with people who are building a 5000-6000 sq ft home with the hot water needs of a laundromat. If we want to talk about energy, bad for the environment, etc. let's start there.

Natural gas, burned in 90+ efficient appliances, will be a reasonable choice for at least the next 50 years.

Heat pump water heaters often have electric resistance backup elements to improve performance but this is also included in their Energy Factor. The two HPWH models I posted have lower energy costs than any available gas models in almost all markets.

Hard to know what is being called misinformation but guessing it's the added dangers of gas. Just to be clear, I don't think indoor gas supply leaks or gas explosions are the main risk. Backdrafting causes the most trouble:

This happens even with perfectly installed combustion appliances and it's more common than most people realize. Most exposure is very low levels and goes undiagnosed but my ego will always strive to make people aware of this common condition and don't feel it's misinformation to point out that it can't happen with elimination of indoor combustion.

OP might be considering direct or power vent appliance, but vast majority of gas water heaters are atmospherically vented. In my experience the risk does not disappear with direct vent appliances. A recent project of ours has a tankless water heater that will not operate when the kitchen vent hood is on. This is a safety feature built into the water heater and if it fails, it will backdraft.

Jake if you have any links backing up your math on the 50% threshold, I would love to read them but I feel that's an arbitrary threshold. Many projections show 50% in only ten years. If that can't happen without utility scale storage why not address the solution of a tank water heater? Choosing an electric tank and enrolling in utility demand control is a much more responsible decision than installing gas. I would only recommend that if there is no place for a heat pump water heater, the best water heating investment available.

Jake, he's not a bright guy, he's something else. Don't waste your time. I'll call out his BS when I see it (which is most every post) and let it go at that.

You're right in saying that he has no credibility with the nonsense he spews.

There are people in many occupations who, lacking real knowledge and expertise to win over customers/clients, try to get ahead by scaring people with distortions. It's trite and obvious as heck, you know it when you see it.

I've known a lot of busy and successful contractors and other than those in retirement, none have time for internet activity.

Hi, all,

I'm not intending to enter the gas v. electric argument nor advocate either as a means for saving the world from global climate change. Rather, I'd like to offer a possible root cause to help Springtime diagnose problems with the tankless hot water heater he referred to.

The current building code in our area requires a make-up air system for any cooktop/range vent hood with an exhaust capability of more than 400 cfm (by way of calibration, that's an exhaust rate equivalent to 5 1/2 of our Powder Room vent fans all operating concurrently.) If the home is a really tight home, you may want to install a make-up air system even if the hood exhaust rate is less than 400 cfm. You can test whether that's the case by leaving a window or door open, running the cooktop/range and seeing if there's still a problem with the water heater when the cooktop/range is operating.

Condensing-type tankless hot water heaters typically have a dedicated supply line for combustion air and a dedicated exhaust. So, if you've got one of those installed, the operation of the hood shouldn't affect it. If you have a non-condensing-type tankless unit, you either need to install it on the exterior of the home or you need to ensure an adequate supply of combustion air to it. If it's installed in a garage, our code official wants an open vent in the garage foundation wall for this purpose. If you've got that, the cooktop/range hood shouldn't be a problem.

If the cooktop/range is gas (gasp!) then it could be a matter of low gas supply pressure to the tankless hot water heater when both are operating--not a direct consequence of the vent hood operating.

We recently had a difficult to diagnose problem with one of two condensing-type tankless hot water heaters installed in the garage of a home. One unit kept shutting down at random when no other gas appliance was operating. We monitored gas pressure when both hot water heaters were operating and it was within spec for normal operation. It turns out it was a flaky ignition module in the unit--nothing to do with gas pressure or combustion air supply.

Hope this helps.

Just a small side note - some of us do live in localities with well more than 50 percent renewables or zero carbon. True of much of Canada and the Pacific northwest and some other countries.

Thanks for the expert comments, Charles Ross Homes. People with knowledge and expertise as you have of course do exist.

armoured, the good or bad luck of geography and weather of course play a part. Especially with hydroelectric power in areas with a lot of precipitation and water, the dams were built decades ago to take advantage of what was available, not because of ecological concerns. In today's light, many of those dams were ill-advised because of their effect on wildlife (especially fish) and remain controversial. You may know that for that very reason there are dams on the Klamath River and elsewhere that are being removed and likely more will follow.

As a different result of luck of geography, the windy Midwest (of the US and Canada) are taking advantage of wind power and places with more sunshine than rain (where I live) look to solar power as the long term solution. As always, the best result will be a balanced mix.

Charles Ross, thanks for raising the issue of Make-up Air. It's a nationwide life-safety building code for homes with vent hoods over 400CFM.

The Make-Up Air requirement exists due to danger of backdrafting indoor combustion appliances.

The project I mentioned has a code-approved and inspected Make-Up Air MUA system. The gas supply has nothing to do with the problem. When the vent hood operates, there is still enough negative pressure to shut down the tankless water heater. Functionally, this is annoying for the homeowners because they cook often and can't use hot water with the vent hood on. It also highlights this important health concern.

I believe David Cary had a MUA malfunction that was missed by code inspections. This issue is a major reason people should be doing Energy Star certifications or having a third party HERS rater verify that mechanical systems are operating properly. It's unfortunate many builders don't see the value and importance of Energy Star. Those building new are wise to strive for a third party certification that uses Energy Star as a minimum.

Our HERS rater verified the MUA damper was operating and advised adding a powered fan to the MUA system at the final walk through. This would have been a big cost and the homeowners decided against it. The rater also found that the ERV was misducted which was an easy fix.

So even with a code-approved MUA system, a direct vent combustion exhaust can be backdrafted. A simple explanation is that the intake duct system is not enough to balance the pressure of a powerful vent hood. Add fans, make the intake duct bigger, ensure good ductwork, keep intake screens clear, put dampers and fans in easily inspectable locations.

MUA introduces another mechanical system that should be commissioned and will eventually break down and require maintenance. I've found that some homeowners are good at this but most aren't. Most people will have no idea when the MUA damper fails, and it will fail.

MUA is a better-than-nothing solution to the problem of indoor combustion. I'm glad that building codes recognize the danger of backdrafting combustion appliances. Hopefully other readers will too and looking forward to the day when MUA systems are no longer necessary.

@Springtime, if the water heater is a sealed combustion device (I think all condensing-type tankless units are sealed combustion devices) then I don't understand the physics of how it is backdrafting due to the operation of a vent hood in the living space. Please advise.

Gas water heaters, like most combustion appliances are not airtight. "Sealed" is a misnomer. That's why manufacturers are now adding electronic controls that shut down the water heater when they sense backdrafting conditions. It's more about combustion appliance housing than vent pipe configuration.

Our rater who is also a mechanical engineer says that tankless water heaters can backdraft at 50 Pascals of pressure. I read somewhere they can backdraft at less than 30. When you can achieve 50 pascals with a C ring, it's not surprising a strong vent hood can overpower a passive intake duct.

To be sure, atmospheric vented hot water heaters are subject to backdraft. I can't find a single reference to substantiate that sealed combustion devices are subject to the same.

Those claims again are just egregious. A hood with 600 cfm fan and no make air can cause negative 3 to 5 Pascals. We are concerned about that because natural draft appliances can backdraft at 3 - 5 negative Pascals. After 600 cfm codes require make up air. To reach 50 Pascal's equivalent to dozen hoods running all at the same time or the 50 pascal blower door testing that
depressurizes houses to 50 Pascals. Not an everyday occurrence.

Just a minor point. When we were looking for blowers, our options were 1200 and 1500 CFM. I don't think 600 is considered acceptable with a significant gas range in 2019.

I got the MUA working but a window crack still causes a significant breeze.

Not to muddy the waters but the negative pressure would have everything to do with how tight the house is. My last house (which met Energy Star blower test in 2009) did not have as noticeable effect when you opened a window even without MUA.

Now 50 pascals seems like a lot. That is blower door test. I certainly can't pull 50 even if I shut off the MUA.

None of it matters. Electricity can be made in a renewable fashion and natural gas cannot. Mandates will come in the lifetime of your house (and possibly appliance). Smiley face emoji.

BT, you should be concerned with both your natural draft appliance and the leakiness of your structure. Natural or atmospherically vented water heaters can backdraft as low as 1 Pascal. A house that can only achieve 3-5 Pascals with 600 CFM suggests a leaky or poorly built building envelope. We regularly get to 50 Pascals with less CFM than that. The MUA requirement is for 400CFM not 600.

All sealed combustion appliances will backdraft, it's only a question of under how much pressure. Install any combustion based appliance inside an airtight enclosure and you will be able to measure when the blower door or duct blaster begins to suck air through the vent pipes and combustion appliance housing. With traditional gas water heaters backdrafting at 1-6 Pascals, 30-50 Pascals seems about right for current "sealed combustion" appliances. Take some apart, it's easy to find airflow pathways.

One might say sealed combustion is 30-50X tighter than atmospherically vented models. I don't think that translates to 30-50X safer due to on-site labor installation and deferred maintenance variables.

Considering atmospherically vented combustion is still legal, there is little reason for building researchers to waste resources on sealed combustion appliances but I did dig up this older HEP article of sealed combustion furnace CO leaks. With increasing trend of efficiency (tighter) homes and powerful vent hoods, there will be more cases like my anecdote.

I do feel sealed combustion appliances are safe enough to include in most homes, but we refuse to include atmospherically vented models. My point is that combustion is now more expensive than all-electric in most markets and indoor combustion always adds risk.

Even with "sealed combustion" appliances and vent hoods under 400CFM, building codes will require Carbon Monoxide detectors for detached garage homes. Yet another cost and maintenance problem. Proof that combustion appliances add risk while all-electric is safer.

Some of our clients and many posters here feel the risk is worth taking and that's fine. I think it's important to make people aware that there are better choices for society, added Indoor Air Quality risks, and probably higher overall costs with gas.

I've done some quick and rough calcs on how to compare natural gas heat output and cost of electric heatpump. The bottom line is that gas is usually cheaper even than heatpump, but it depends on actual electricity and gas prices. Warning: this is a rough estimate only and I hope I made no errors. It does not apply to propane or fuel oil – heat pumps may be quite a bit more competitive there. Criticism or corrections (hopefully constructive) would be welcome.

This is rule-of-thumb info, not definitive. The output number is Coefficient of Performance - and needs to be read the following way: "if my heatpump water heater’s actual, delivered performance on average would be greater than X, I would save money on operating costs." Note: this is only operating cost, no info about upfront or lifetime costs. If there are other service costs like monthly meter fees, would have to be incorporated.

Method: take the cost of electricity in dollars per kwh (use average expected for actual use), and divide by the cost of gas in dollars per 1000 cubic feet. Multiply this by 360.

Or in one step: Electricity price (US$/kwh) / gas price (US$/kwh) *360. [Careful to use $0.10 for 10 cents per kwh]

If you believe the CoP of your heat pump water heater will be higher than this number, there should be operating cost (fuel) savings.

Example 1: US$0.12 electricity price / $9.5 gas price * 360 = ~4.5. [Note these are figures I found for average residential delivered prices in USA.]

Meaning: the average CoP (coefficient of performance) would have to be 4.5 on average to see fuel/electricity savings. This would be a very high real-world CoP - probably unachievable.

Example 2: US$0.05 electricity price / $12 gas price * 360 = 1.5. This is a CoP which is almost surely achievable, year-round, particularly in a moderate climate - but it's based on a quite low electricity price. (You'd get similar result if you had expensive gas)

For an even simpler rule of thumb: if the price of gas in dollars is more than twice the price of electricity in cents (ignore the cents/dollars), a heat pump water heater should be competitive to natural gas hot water – the CoP needed to save would be less than two. If the gas price in dollars is close to the electricity price in cents, the implied CoP climbs above 3, which sounds less reasonable as a ‘real world’ heat output for a residential heat pump – so if the gas price is less than the electricity price, it’s probably not going to pencil in at all.

Gas price to electricity price ratio of 1.5 gives a COP of ~2.4, which may be a reasonable guess for the break-even point. If you think heat pumps are way more efficient than this, use your numbers.

Assumptions: energy content of 1000 cubic feet of natural gas is 293 kwh. Boiler efficiency is 82%. (Note the 360 is rounded for convenience from this conversion factor, which is actually energy content divided by efficiency to give ~357). If someone has different figures for energy content of gas or efficiency for the boilers that you wish to use, go ahead.

Other key assumption: I’ve assumed that ‘real world’ CoP for a heat pump above 3 is pretty unlikely, and that close to or below 2 or 2.5 is quite likely feasible, depending on climate. (Warning, since a heat pump water heater uses heat from the house if installed within the building envelope, it’s a parasite in winter but helping in cooling season – those in climates where A/C dominates get a net benefit, those in climates with no A/C / mostly heat demand are losing).

Obviously the above can be restated in metric (which I'd prefer) but I'm too lazy.

To folks whose only tool is a hammer, the world seems full of nails.

And someone who feels they have magically found what they think is enlightenment that the masses know little about believe it's their mission to preach the word by castigating those who have a different point of view. Often a more balanced and sensible one than what the enlightened ones follow.

armoured, I think you'll find it easier to think about the cost comparison on a BTU cost basis.

If in the PG+E area, OP will find using gas for heating water is much cheaper than using electricity. Perhaps OP is in one of the municipal districts with lower rates and if so the result may be different.

I don't understand, are those comments directed at me? I'm not trying to push anything, I just found the claims about how heat pump would be cheaper weren't based in the math to compare.

And for that, the main inputs are the relative cost of gas vs electricity and what CoP a heat pump water heater could achieve. As far as I can tell, that isn't often the case, but might be in some places.

As for approaching the calcs using BTU, whatever works for you, the result should be the same. Anyway, hope the calc is useful to someone, although it's only a start in comparing.

Armoured, the first paragraph? No, not at all. Sorry if unclear.

BTUs - 1 therm of gas (the normal billing unit and roughly 100 cubic feet) = 100,000 BTUs. Remember that gas heaters are either 67% or 80% efficient so heat potential is lost. But recovery is much faster.

1 KWH= 3400 BTUS if produced by electrical resistance, about 10,000 BTUs for a heat pump. When an electric tank is recovering from use heating cold water, I suspect the heat is supplied by both so maybe an effective production is at the average - 6500 BTUs per KWH? Or maybe it's more resistance and less heat pump and the cost is higher?

In the PG=E area, the cost of a marginal 1 KWH is 29 cents. 1 therm of gas is $1.20 or $1.80, depending on use. Use more, the rate goes up.

1 term = 100,000 BTU at 95%efficiency (on demand) 95,000BTU. = 0.001263157 cents per BTU

1 KWH = 3400 at 80% (tank efficiency) = 2720 BTUs price (29 cents) = 0.01 cents per BTU

At $1.20 per term gas a LOT cheaper than electric

Now in my area electric is 8c kwh and NG 1.20

Electric tank 0.002, but if you use HPWP has coop of 4 = that would 0.0005/BTU making HPWH cheaper than NG.

You are of course comparing NG tankless to electric resistance tanked. Just so we are clear.

That is a no brainer on cost per use.

The HP is not likely to get to COP of 4 - except a Miami garage. Then it might be higher.

There are a lot of variables as someone mentioned when it comes to the space the HP is in. We have it in an insulated attic on the south side of the house. So it helps in a/c season.

> The HP is not likely to get to COP of 4 - except a Miami garage.

I know that, but this is what manufactures are claiming. I think they will be more on level with gas, except for much slower recovery. After 3 floods I hate tanks [2x water heaters and one craftsman water softener tank split]

I find it more intuitive to compare using relative prices (gas vs electricity) to see what the implied COP is rather than use BTUs, but that's just a slight rearrangement of the formula.

@Elmer, you said 'actual BTU output' from the heat pump might be about 2X resistance, that's basically just restating the COP approach as BTU (and both work).

After that, one would need to do a bit more work to figure out the savings based on annual consumption and fees like fixed monthly charges.

I agree with the point that the actual COPs will tend to be lower than the manufacturers' estimates. I read a 'real world' study for the NorthEast US recently, which had a pretty wide range for COP from 1.7-2.5 COP (as I recall). I presume this includes any energy used by the resistance backup and I believe the study mentioned that actual results depended on factors including total hot water usage and timing. Obviously warmer localities would have higher average COPs. Another study for Canada - obviously mostly colder - estimated that in most cases where heating was gas and the heat pump water heater was in the building envelope, it was often a net loss (what I called parasiting off the home heat). Places with resistance heat, fuel oil and propane were prime candidates though.

As someone else noted, if you're running a dehumidifier or A/C much of the year, you're getting a benefit from the heat pump, and probably higher COP as well.

That last paragraph from Armoured sums up the bottom line $ well. Locating Heat Pump Water Heaters HPWH in conditioned attics like David is brilliant design strategy. Locating them in below-grade spaces like tall crawls and basements help address the higher moisture loads there too. Large pantries can benefit from the cool air of HPWH with care applied to potential of extra noise.

Running AC much of the year and having dehumidification needs describes most of the country. With most of US population living and growing south of building climate zone 5, it's safe to say HPWH can easily beat gas in overall energy costs for majority of country with smart design.

Even ignoring the beneficial space conditioning of HPWH vs negative risk of combustion exhaust from gas appliances, fuel costs can end up in HPWH's favor when considering the most efficient HPWH models in new construction. Most of the south has cheap electricity and moderately priced Natural Gas NG compared to northern climates. Rather than math it all out, here is a comparison based on actual measurements.

This Consumer Reports article represents a good average for most of the country with the Tankless NG annual cost of $195 appearing to edge out the HPWH costs of $240. Those are simple fuel costs. Fair accounting of total fuel costs includes the minimum fee charged by the gas utility.

This AGA report says minimum, monthly fees in 2015, averaged $11.25 but real cost to utilities was $24 and rising. Assuming average existing (inefficient) home with 33% of gas used for water heating, means adding $44.55 (.33*$11.25*12) to actual fuel cost of tankless NG at $239.55 dollars per year. An efficient home with a decent heat pump used for space conditioning results in a higher percentage of gas costs for water heating, tipping fuel costs in favor of HPWH. Net-zero designed homes often see higher water heating costs than space heating.

Most in this forum are doing new construction. Any amount of money spent on NG infrastructure faces dubious simple payback. Infrastructure costs are often hidden in the building budget but here are some extra costs associated with running a gas supply line from the street to your appliances and dealing with resulting indoor fossil fuel combustion exhaust: Trenching, backfill, pavement/drive repair, erosion control, supply pipe and labor street-to-house (often utility provided), supply pipe building envelope penetration, drop fee from plumber/HVAC per appliance (interior piping and venting), combustion exhaust venting material, exhaust vent building envelope penetration(s), wall/roof caps. We have done homes with NG infrastructure costs running into the thousands, mainly due to required deep trenches through difficult terrain. Figure couple hundred minimum.

I agree with the CR report that tankless are rarely worth the investment. They are maintenance prone largely due to yearly flushing or water softening requirements. Tanks are generally more reliable and don't share the many performance problems that come with tankless.

Slow recovery and first hour ratings are addressed with bigger tanks. The 80 gallon Steibel Eltron Accelera HPWH has 147 gallons of 104F water immediately available with first hour rating of 74 gallons. This is very impressive for one of the most efficient water heaters available and offers more than enough hot water performance for most families.

A final point of enlightenment addressing the contemptuous climate change comments. NG is also bad for society in part due to fracking contamination of rural well water. If you live in cold climate with no basement or can't design the right spot for a HPWH, explore option of integrating an electric tank with your electric utility. Be part of solution, not problem. This could be a great excuse to get rid of your gas water heater!

Wow, so let's be clear about some things: I'm very much in favor of cutting carbon emissions as anyone. I've also said that heat pump / hybrid water heaters are a good idea in many applications.

But there's a lot of nonsense here.

As has been stated and shown with math - until our grid hits 50% renewable, electric resistance (not heat pump) is worse for the environment than natural gas burned in a 90+ water heater or furnace.

As long as this country is pumping oil, we will need a market for the natural gas that is found as well. Getting rid of gas appliances doesn't do anything to reduce the fracking issue. What NG we don't use domestically we will turn into LNG and ship to other parts of the world - which is a LOT more resource intensive. Using NG as a fuel is much better than burning it off at the well, which is happening in some areas already because there isn't a distribution system to get it to market.

We have about 30 years to become carbon neutral (which isn't very long at all).

Within 20 years, most of our nuclear power (20% of our current electrical source) will be retired - and there are no new nuclear plants being built. Whatever you think of nuclear, it doesn't produce carbon.

Also within that 30 years, much of our land based transportation will certainly have gone electric.

There is a massive demand for renewable power over the next 30 years - both to fill the 20% that is nuclear now, and to power transportation (electric cars). Even though renewables are growing, we are not building nearly enough renewable energy to fill that demand AND we don't have utility level storage worked out. Until this gets a solution, natural gas in a 90+% appliance is our next best option.

To complicate matters - Europe is already buying 40-60% of their natural gas from Russia, and will completely run out in 50 years - which makes them subject to some ugly geopolitical issues as well. We are ramping up our LNG exporting capabilities, but we can't supply Europe.

If I had to summarize, I'd say stop building homes with crazy energy needs in the first place. Stay flexible on fuel supply, install efficient appliances and install renewable energy such as solar (or opt-in to buy it from your utility).

@Jake "...there's a lot of nonsense here." Amen.

Perhaps the most nonsensical comment is Springtime Builder's claim that "Locating Heat Pump Water Heaters HPWH in conditioned attics like David is brilliant design strategy."

In the real world, water heaters and associated piping will leak at some point in their life. Locating them in an attic--conditioned or otherwise--makes the consequences of a leak more costly to address. And if the attic is accessed via pull-down stairs, it will probably be impossible to get a replacement tank-type water heater through the opening.

Plumbing in attics is a bad idea not a brilliant design strategy. Insurance companies should tack on a premium for insuring any home that has one.

Springtime Builders, can you share the reasons, if any, the Stiebel Eltron should be considered instead of the Rheem Performance Platinum Series? My understanding is the Rheem has a higher UEF and is quieter... will the Stiebel last longer and does it have higher quality components?

I'm about to embark on a new build in Tampa, FL. We will be electric only and my current plan is to put the HPWH in the attached garage... trying to decide between 50 and 80 gallons. I'm also contemplating an on-demand recirculating pump for instant hot water at all faucets.

By that reasoning, we shouldn't build multi-level dwellings. Or if we do, locate plumbing on lowest levels only. Should insurance companies also charge premiums for attic air-handler units? What about sprinkler systems?

Tank water heater leaks are addressed the same way as heat pump air-handlers: drain pans. When possible, we try to pipe secondary condensate lines of air handlers and water heater pans to an obvious location, even above a door or window. Homeowners are more likely to recognize a problem. Tucked away in a lowest-level corner, leaks can take longer to detect.

I'm still a fan of vented attics with the right design and obviously, water lines don't belong in spaces that see freezing temperatures. Good designers and builders ensure correct spaces for mechanicals. Tanks in attics require extra planning.

Perhaps some view the problems of conditioned attics (unvented) the same way as climate change; if you can't see the problem, it doesn't exist. Humidity rises, and problems with conditioned attics are becoming better understood. Conditioned attics usually use spray foam and building researchers have documented how moisture is causing problems in this increasingly popular attic construction. In Alison Bailes words, "The days are over when you can spray open cell foam in an attic, close it up, and walk away."

Not sure if international code has passed it yet, but best practice is to provide an HVAC supply and return to conditioned attics. Another best practice is to locate a heat pump water heater in the conditioned attic. It keeps the space drier and gets a performance boost from warmer temperatures. It could negate the extra HVAC needs of conditioned attics. Symbiotic, house-as-system design strategy.

Similarly, an electric resistance water tank can be used to clean up the electric grid by storing excess renewably generated energy. To completely dismiss that option in favor of gas ignores our energy future, risks higher costs, less durability and lower hot water performance.

Natural gas is being fracked indepently of oil production. Less demand equals less produced. Using gas peaker plants to replace coal is one thing. Piping gas to new, residential construction and burning it inside efficient homes is nonsensical.

Sorry Sbiller, must have been composing last post as you posted. Yes, I think Rheem model has better UEF and decibel rating. Decibel rating shouldn't matter in your attached garage.

I would almost always recommend the 80 gallon or biggest available capacity for all HPWH models, unless it's a single member household with low water usage. Bigger HPWH tanks are more efficient and help address slower recovery.

I think the energy ratings are close enough to dismiss. The real question to me, is will the extra cost of the Stiebel Eltron, payback through better durability? My feeling is yes but only time will tell. The Stiebel has no electronic controls, only a dial that controls temperature. It's been around longer and online ratings are limited but almost entirely favorable. I would choose the Stiebel if durability is more important than upfront costs. Head's up: it's a heavy appliance.

Need to do more research on that Dmand product but looks promising, as long as the circulating pump is activated by a switch or motion sensor. Would be concerned about added complication compared to a small, plumbing footprint but probably a good solution to common first world design problem.

The climate here in coastal Virginia is fairly mild, but we do get sub-freezing weather that can last a couple of weeks. Many of the retired folks who live here retreat to warmer climes when that happens. It is all too common for a water line supplying a hot water heater or a humidifier in one of their (unconditioned) attics to freeze and cause the pipe to burst while they're away. They come home to a major inconvenience and an insurance nightmare.

The same scenario can play out in a conditioned attic if we get a prolonged power outage during a cold snap.

Even if we can't eliminate the failure mode (the frozen water line,) we can minimize the consequences of a failure by locating the hot water heater in a space such as a garage or for a tankless heater like mine, on the exterior of the home. If avoiding the insurance nightmare and inconvenience aren't enough reason, consider that the embodied energy in the various building materials that would otherwise by destroyed due to the leak isn't wasted.

Springtime, thanks for the response. It helps my understanding and the additional suggestion on the 80 gallon versus the 50 gallon is helpful.

"Similarly, an electric resistance water tank can be used to clean up the electric grid by storing excess renewably generated energy. To completely dismiss that option in favor of gas ignores our energy future, risks higher costs, less durability and lower hot water performance.

Natural gas is being fracked indepently of oil production. Less demand equals less produced. Using gas peaker plants to replace coal is one thing. Piping gas to new, residential construction and burning it inside efficient homes is nonsensical."

Enough made up garbage from you, bud. Have your own opinions as you wish but few agree with you and repeating the same baloney over and over isn't convincing anyone.

Sbiller, by all means, get expert advice. The words from the Springtime BUilders fellow don't fall in that category. Use experts on your job and take their advice.

Re: electric water heaters being used to 'clean up the grid.'

There is a relatively new standard communications/control port, ANSI/CTA-2045, that is intended to be used to allow for demand response - either turning the hot water heater on or off in cases of excess/deficit demand (or other uses such as smarter time of day). My understanding is that this is pretty new and not commonly found, and not many utilities ready to implement (although lots of pilot projects and tests). In theory, mass implementation would add a lot of flexibility to grids. But again, I don't think widely adopted.

https://www.usnap.org/mission-and-purpose

Note, I don't think it's limited to just water heaters.

Armoured - increasing solar installations changes everything in regards to demand management. This is a new problem and while utilities are just starting to study it, they are doing so because they realize that is the future.

Living with renewables only requires significant investment in demand management.

There is some truth to every argument (ok not always) and insults to random people on the internet just shows someone's true colors.

Anyone who has looked at climate change and what needs to be done knows that you can't get carbon free by burning natural gas. Now you can argue that we are never going to do it and we are all doomed. And you can argue about the geopolitical issues regarding Europe and NG.

It is fairly well settled in the green community that tanked electric hot water can be a very green choice. Just because we still burn a lot of coal doesn't change the fact that electricity can be generated in a renewable manner and NG cannot.

Springtime isn’t my only source of info which leads me to use a HPWH. I was looking for some insight into the difference between the higher price German brand and the more prevalent Rheem HPWH. That info isn’t readily available.

Individual actions to make one home a bit more efficient or to choose this approach or product over that one that one are laudable but in the grand scheme of things, are meaningless and just feel-good efforts. Unless you live in a region with extreme temperatures, there may be no payback during the period the home is owned.

In the US today, we have politicians at all levels who deny climate change, continue to favor and promote coal producers (insert face palm moment) and dismantle longstanding EPA and other environmental rules.

The two guys here who would claim being on a first-name basis with the Lorax just repeat the same mantras as if standing on the Mountain of Righteousness and looking down at the heathens. So many building decisions are compromises. Too many people go in the direction of putting in things that are not the best choices IN THEIR CIRCUMSTANCES but do so simply to be able to crow about them. Some here demonstrate that attitude.

If you want to do something that matters, don't fret over which spray foam is better or the R value of your windows. Get active with the organization of your choice to make a difference in governmental policies and practices. Vote, for politicians who share your views and against those who don't.

sbiller1

Springtime is an evangelist -- and that's ok up to a point. But much of what he says is misleading.

I've never been a big fan of Stiebel - but I haven't used their Accelera units.

One of the big issues between the two is that the Stiebel units don't have a significant resistance heater. You basically have "heat pump" mode only. Recovery is slow - so you need the 80 gal. On the plus side, you only need a 20 amp circuit.

I have been a fan of Rheem in general, although I haven't used their hybrid heater.

The Rheem does have the upper and lower element that will speed recovery time, if needed, or if there is any issue with the heat pump. Of course then you have a standard electric heater. You need a standard 30 amp 240 v circuit because of the upper and lower elements that may be used.

The Rheem also has leak detection and some interface with your phone.

You will get the most energy savings if you use the larger tank. The reason is that using the heat pump is slow recovery. The Rheem will kick in the resistance heat elements if demand calls for faster recovery

The larger tank allows the Rheem to supply hot water without kicking in the resistance heat elements as often.

Funny to be accused of evangelism by poster that incited an "Amen", a few posts up :) Always appreciate feedback and constantly working on preachiness of writing style. I think including links or reading opines without sourcing helps others decide on misleading comments.

It looks like Stiebel updated their Accelera HPWH to include an electronic control screen since we bought one a couple years ago for parents house. After an updated check on reviews I still feel safer with Accelera but it's hard without knowing volume of units sold. Surely Rheem has sold more HPWH than Stiebel at this point, despite Accelera being around longer.

Reliability is a compelling reason to go with Rheem Marathon an electric resistance tank. Best warranty and most well-reviewed water heater available. Tank size plays a role here too. Bigger tank means better hot water performance, with minor hit in efficiency. The bigger the tank, the better for grid storage and demand control.

Demand control has been around a long time with the most basic strategy using a timer and time-of-use billing options through utility. Studies will continue forever on more advanced grid-smart water heating technology but at this point, it's a time-tested technique with this smart water heater article quoting up to one million in use already with potential savings for homeowners and grid. Another article from same site points to irony of battle between grid storage potential of simple electric resistance tanks and the efficiency of heat pump water heaters.

In that first article the Hidden Battery link seemed misdirected but it was put out by the NRDC pointing to potential of electric tanks to reduce the need of new power plants and grid storage for renewables. Large, reliable electric resistance tanks are becoming more of an asset while gas is becoming more of a liability.

I think most of this forum's posts could be described as meaningless or feel-good-only but definitely not water heating. It has large environmental and social consequences. It's one of the only home purchases capable of beating the stock market for returns on investment. I think the ROI currently lies with HPWH but the second best choice could easily be a good ole electric tank.

If an electric utility offers good incentives, electric tanks like the Marathon, could beat tankless gas or HPWH in total lifetime costs including repairs and replacement. A home equipped with PV panels and Marathon tank could also be in the running as best long-term water heating investment.