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Community and Q&A

Replacing a Gas Water Heater

Steve Knapp CZ 3A Georgia | Posted in Mechanicals on

For context, we bought a townhouse in 2018 that needed a lot of updating. I went overboard on those projects and then had to take a financial hit when we decided to sell on in 2021.

Now, we are buying another home where all the mechanicals are at the end (or beyond) their typical service life. The water heater, for example, is a Fury 40 gallon gas model installed in 2007. It’s in the garage where an eventual leak wouldn’t be much of an issue.

If I had my druthers, I’d swap the Fury for a new 65 gallon Rheem HPWH. It would need a new dedicated 220 VAC circuit, and I’d prefer to duct it to the outside to maximize efficiency.

FWIW, I’ll probably replace the two malfunctioning gas furnaces with a single ducted heat pump. The kitchen is all electric and will stay that way even after we update the appliances.

The “cheapest” solution is probably to wait for the Fury to die and then replace it with another gas water heater. But then, it’s likely I’ll be paying a monthly gas connection charge for a single appliance.

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Replies

  1. Charlie Sullivan | | #1

    Do you have a 120 V outlet nearby? 120 V HPWHs are supposed to be on the market soon if not yet.

  2. Steve Knapp CZ 3A Georgia | | #2

    Hi Charlie,

    There should be a plug near by, but the Rheem 15 amp hybrid is still 220 VAC. I couldn't find anything on their site about a 120 VAC version. Do you have a link?

    1. Charlie Sullivan | | #3

      Here's an article that says multiple options will be on the market in the first half, maybe first quarter, of 2022.

      https://cleantechnica.com/2021/11/29/120-volt-heat-pump-water-heaters-hit-the-market-make-gas-replacements-even-easier/

      1. Steve Knapp CZ 3A Georgia | | #5

        I'm feeling this article may be working off of Tesla timelines. ;-) But maybe one of the manufacturers will surprise me.

  3. Paul Wiedefeld | | #4

    Financially, this decision heavily depends on that monthly fee. Think of it as a guaranteed return similar to a CD - your utility will not cut that rate (probably will increase it). If it's $10/month, that's worth around $1140 if you plan to stay there 10 years. Double that if it's $20/month. You also have to compare a 60ish% efficient gas appliance vs. a 350% efficient electric one for operating costs.

    In terms of safety, you're avoiding an appliance that can harm you with carbon monoxide.

    For the climate you're replacing a high emitting appliance with a low emitting one.

  4. AMorley | | #6

    If you are pretty sure you will swap the furnaces for a heat pump in the next couple of years, it might make sense to bite the bullet on the HPHW heater now instead of in another decade. Gas utilities are likely to start charging substantial disconnect fees, as electrification accelerates in the coming years.

    Oklahoma Natural Gas is leading the way on these fees, proposing a nearly $700 disconnect fee in order to stave off a customer attrition death spiral, after they incurred big costs this past winter. More utilities will follow suit when they get the chance (and excuse).

    Get out while you can!

  5. Walter Ahlgrim | | #7

    Seems to me like maybe the last house had some lessons for you.

    I don’t see the big rush to replace the water heater before it time.

    In most locations pulling the gas meter and going all electric is a poor economic decision likely to result in higher monthly bills and lower resale value.

    It seems very unlikely Oklahoma Natural Gas will get that type of disconnect fee approved by the regulators or courts.

    Walta

    1. Paul Wiedefeld | | #9

      I doubt anyone cares much about gas at resell (whenever that may or may not be) if the kitchen is already electric.

  6. Steve Knapp CZ 3A Georgia | | #8

    Hi Walta,

    It was a learning experience, yes. I'd probably skip spray foaming the attic and garage ceiling if I had a do-over. The other projects were more essential to making the house livable.

    On the gas, I don't have to pull the meter. The service is always there if a future owner wants to turn it on.

  7. Walter Ahlgrim | | #10

    My point is the last time I was searching real estate the MLS had a big box to check for gas heat making it easy for buyer to skip the all electric homes if they are so inclined.

    No box for geothermal.
    No box for heat pump.
    No box for solar.

    Why because the market demands a gas box. Some of us may disagree but we would be fools to ignore what the market is trying so hard to tell us.

    Walta

  8. Expert Member
    Akos | | #11

    If the existing 15A feed for the gas heater is dedicated, it is pretty simple to upgrade it to 240V. An electrician can swap out the breaker to a two pole on the panel and tape mark the existing neutral wire as hot. This would give you the 240V 15A service you need for the new water heater.

    1. Steve Knapp CZ 3A Georgia | | #12

      Great suggestion. I'll look into it.

  9. John Clark | | #13

    I would wait because I would want to see how high electric rates jump once the new uber-expensive* nukes at Vogtle go online in Q4 2022/Q1 2023.

    * $13B in cost overruns.

    1. Expert Member
      Zephyr7 | | #14

      There probably won't be any jump, especially if the new capacity is used to mothball some older, less efficient generation, which is often the case. Those construction costs will typically be amortized over the life of the plant's operating license, which is normally a 40 year term. The license can be extended for additional 20 year terms, which is likely to happen. These types of plants are expensive to operate, but cheap to run, and are used as baseload generation -- generation that is ALWAYS running. Baseload plants are the cheapest plants to operate.

      I do wonder how they managed to run up so many overruns. I know these plants are complex, but I would have expected more things to be caught and addressed during the planning phase. I've been involved in very large scale projects somewhat similar to this in the past, and there are years of planning and design work prior to breaking ground. The goal is to avoid any surprises once the construction work starts.

      Bill

      1. Paul Wiedefeld | | #15

        These overruns are precisely why new American nuclear is such a dead end! If you game this out: who gets to build the next reactor? The Vogtle firm (they have the most recent, relevant, yet terrible experience) or someone else (who just witnessed a train wreck and will bid accordingly)? That’s for the next reactor. If we want to double our nuclear capacity over 20 years, we need about 100 reactors breaking ground very soon. Would anyone want the 100th best team working on their reactor?

        Meanwhile, solar did almost 20 GW last year and more this year, with wind not far behind.

        1. Expert Member
          Zephyr7 | | #16

          Then these issues need to be fixed. Solar and wind aren't going to do it. Solar and wind are a very, very small percentage of the total mix, and aren't going to be able to replace everything. There need to be other options.

          As an interesting related item, I recently calculated (for another forum), the amount of new electrical generation that would be required to replace all of the gasoline used for transportation in California alone. Even using a very overly-favorable estimate (which assumed all existing generation could operate indefinetely, all new load was during off peak, etc.), California would require 41.7 GW of new generation (which is about four times the capacity of my entire electric utility here in SE MI). A more accurate estimate allowing for maintenance and other issues is probably to allow about double that amount of new generation. That's only to replace gasoline too, not diesel which runs all the heavy stuff. The energy requirement was about 1,368 GW/h per day to replace that gasoline.

          I'm not against electric vehicles (I drive one daily), but it isn't realistic to think we can electrify everything and run it all from "wind and solar". That's just not going to happen, and the reason is physics says it's not going to work -- the scale is too massive. It's important to work on realistic solutions, and right now nuclear is our best green option for baseload generation. Wind and solar have their place, but they're not a panacea.

          Bill

          1. DCContrarian | | #17

            We're veering off-topic here, but a book I found very influential was "Power After Carbon" by Peter Fox-Penner ( https://www.amazon.com/gp/product/067424107X )

            It's dense and quantitative.

            He believes we can stop releasing carbon into the atmosphere by 2050. There's no way to replace fossil fuels in our economy, but he believes that carbon capture and sequestration technology will advance to the point that it is practical at the scale of large generation plants. Outside of large plants we will have to stop burning fossil fuels, which means that transportation and heating will have to be electrified, as well as utility uses like cooking and even lawn-mowing and the like. As you note we'll need a lot more generation capacity, which will come from new fossil-fuel plants, nuclear, wind and solar. He's a big proponent of improving the grid and increasing the level of interconnection to get more utilization out of capacity. He's also a proponent of energy storage technologies like molten salt and reversing hydro electric flows, although he makes the case that batteries are not practical for energy storage at scale.

            He is skeptical of rooftop solar and feels that solar farms are a better bet.

            Interestingly he foresees batteries as powering vehicles. If I were looking into electrifying our transportation system I'd be investigating putting wires in the roads and then using batteries just to get from your parking spot to the nearest road with wires.

          2. Paul Wiedefeld | | #18

            Baseload seems more like an artifact of the types of power plants we first built than a requirement: big, constant output coal then nuclear plants that struggle to start and stop. If the combined cycle was invented first, I wonder if we’d use the term. I don’t think using just wind and solar is the ideal, but they’re the most ready today (~40GW/year). I wonder if more US solar thermal is installed per year than nuclear - it’s got to be close.

          3. Expert Member
            Zephyr7 | | #19

            Baseload is reality. Load on the grid has a cycle, peaking during the day, with a low point in the very early morning overnight. The constant portion of that load is the baseload portion. You run the most efficient plants as much as possible, since they're most efficient. Those same plants tend to be cheapest. Admittedly, as far as fuel supplies go, wind and solar are cheap to operated, but they're also somewhat unpredictable. This means they act more as peakers, something solar is especially useful for since it's peak output tends to line up somewhat with peak load times. Neither is entirely controllable though, so they can't be the sole sources.

            "40GW/year" doesn't really mean anything. 40GW is a continous number, a rate. "40GW/h per year" is a quantity, like a number of gallons of water. The first is a big number (although at grid scale, it's not as big as you'd think), the second sounds big, but it's actually very small.

            For example, 40GW is about 4x the generating capacity of my local electrical utility (which has about 11GW installed generation capacity). 40GW/hr is about the amount of electricity my local utility could generate in a little over 3.5 hours, which isn't much. In my original example, 40GW/hr would replace about 42 minutes worth of California's daily gasoline consumption. I see those two units mixed up a lot, especially in green energy articles, and that's a big problem since it can be deceptive. Sometimes the mistakes appear to be honest ones (where the units are used interchangeably at random), but I've seen other articles where the units are being used incorrectly on purpose, to make things look better (or worse). I point this out because we can't make good decisions if we're starting with bad data.

            Bill

      2. John Clark | | #21

        I don't believe any plants are getting mothballed but I may be wrong. The additional capacity is to keep up with an increase in demand.

        There are a lot of articles about this project and the cost overruns. For one it includes the bankruptcy of Westinghouse. Cluster-F best describes it. Even Dana Dorsett has said fueling the damn things would be a big mistake but govt pushed onward. Sunk-cost fallacy on fully display.

  10. Paul Wiedefeld | | #20

    Bill,
    Thanks for your response. "40GW/year" should have been worded “~40 GW of new solar and wind generating capacity were installed in the US in 2021”, I apologize if that was unclear. The important point is that adding capacity (with existing supply chains, human capital, construction ability, financing, etc.) using these energy sources seems much faster than nuclear, which has added only ~100 GW total since the 1960s in the US. Ideally, we would be adding nuclear at high rates too (or had more nuclear to start).
    In my opinion, the term “baseload” when applied to generation (demand is different) needs still seems like an artifact of the coal/nuclear age. If you have a grid of mostly high capital cost, medium operating cost generation with mostly inflexible operating characteristics, it makes sense to keep capacity factors high for the most efficient units, even if you lose money a good amount of the time. If you have a mixed grid with highly flexible, low operating and low capital cost generation, capacity factors can be lower and generation can still be cheaper. Combined cycle gas (depending on gas prices), wind and solar (depending on storage) all fall in this category and more storage will help. Keeping a reactor or coal plant operating nearly 24/7/365 seems suboptimal in both theory and practice, as many of these exact kinds of assets exit the market. A grid with cheap, abundant, and varying types of storage could potentially not have a single baseload generator, which is why it seems like the term “baseload” followed the generation mix, not the grid needs.

    1. John Clark | | #22

      Remember baseload is the amount of power required to meet the minimum level of demand placed on the grid. It applies to both generation and demand.

      1. Paul Wiedefeld | | #23

        Agreed, but it seems married to a constant output generator grid mix. Same with “peaker.” If every asset was cheap and highly flexible it could be just called “demand”.

        1. Expert Member
          Zephyr7 | | #24

          It doesn't work that way in practice though. Solar is very cyclical, and it's a good example because it's easy to see why that's so. Solar is also reasonably predictable though, so you can have a reasonable expectation to get some percentage of your solar capacity online and different times of the day when there is daylight. Wind is much less predictable, which means it can't be relied on in the same way as conventional generation. Neither of these (wind and solar) are similar to any conventional plant (gas, coal, nuclear, hydro), since all of those are pretty much entirely controllable -- they can make whatever their rated capacity is whenever you need them to, regardless of weather conditions. This means they can be relied on to serve load.

          Load is very predictable on a large scale, so generation mixes can be preplanned. The terms "baseload" and "peaker" still apply, since you can still have load peaks (heavy air conditioning demand on a hot day, for example), which may require additional generation beyond what would normally be available -- including predicted wind and solar -- and baseload still applies to the normal long-term load averages.

          You can't just quickly switch between this and that small-scale generators. There are issues with power flow and system stability. Things that seem easy on the small scale are not so easy on the large scale -- it's not easy to just quickly switch/reconfigure 345kv transmission circuits, for example. A certain amount of stable generation is required to ensure system stability, with the more dynamic sources being able to be brought online as available. If you have, for example, an extra windy day, maybe you can idle a coal plant that day. Maybe maintance can be done on that coal plant during peak solar production too. What you can't do is just quickly switch any of that on and off. Big things tend to not want to quickly start or stop, an the electrical system isn't much different than a large mechanical system in that regard. It's not that it's old or out of date, it's that it's MASSIVE.

          Bill

          1. Paul Wiedefeld | | #25

            Thanks again Bill. Still think there’s diminishing relevance to knowing what the baseload demand is versus any other level of demand IF there’s no reliability and slim efficiency benefits to running a particular asset constantly, which is now the case. I think this is demonstrated well in markets like ERCOT, where coal and nuclear generation is decreasing and prices are low.

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