Water heating is a tankless job

An outdoor showerMy abstract thinking about a tankless water heater became more concrete recently when we realized that our (25-year old) water heater was broken. Not just broken, in fact, it was actively spraying water all over the crawlspace. The bad news is that it took us several weeks to realize. The good news is that the crawlspace has excellent drainage, since the water didn’t seem to stay. According to the water company, we used 66,000 gallons of water (usually, we use 1-2 thousand), so we’re glad it didn’t back up! We’re also dreading our water bill.

In the meantime, we had a plumber come out and make a quick $100 fix to the leak. The water heater still didn’t work because of a broken temperature breaker, so Maggie short-circuited it. It works well enough now, we just have to keep the water heater off at the main breaker so that it doesn’t overheat. The part is relatively cheap and easy to replace, but since the current water heater is so old, we decided to see how much it would cost to have it replaced.

Two weeks of phone calls to the plumber later and we finally had an estimate. They said that it would cost $800 to replace the current one with a new electric tank and that there was no such thing as a whole-house electric tankless water heater. $800 seems like a lot and I was pretty sure I’d seen the apparently mythical electric tankless versions, so I did some digging.

It turns out that the natural gas tankless water heaters can give a much better flow rate than electric ones. I’ve seen natural gas tankless run up to 10 gallons per minute with a 55-degree temperature change. Electric ones seem to peak at around 4 gallons per minute.

Still, 4 gallons per minute seems reasonable to me, so I’m not sure why the plumber thought it was impossible. We only really use hot water for showers and doing dishes (and we rarely do those at the same time). A standard shower fixture uses 2.5 gpm and a sink uses about the same, so that would be pushing things somewhat. Of course, the result would just be slightly cooler water, which wouldn’t be terrible either.

And if we got a low-flow showerhead and a sink aerator, we could reduce that to 1.5 gpm and 0.5 gpm respectively. That’s only 2 gpm, which would only require a middle-of-the-road tankless water heater.

Even if we got a dishwasher, we’d only need 3 gpm to make sure it would get hot water. It doesn’t seem like it would be a big deal to avoid taking showers while washing dishes, especially since we only wash dishes once or twice a week.

Or maybe I’m deluding myself and it would it be unbearably annoying to start a shower and then have it get colder as Maggie starts up our (hypothetical) dishwasher. Guests might come over and be devastated that the water got colder when they took a shower at the same time (in different showers, for those of you with dirty minds).

Another possibility is that Maggie and I just don’t use as much hot water as a usual household, so an electric tankless would work perfectly for us. How much hot water do you all use at once? More than a shower and a faucet? I’d love to hear from you to see if our water usage is really that unusual.

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13 Responses so far »

  1. 1

    Andy said,

    August 25, 2008 @ 11:16 pm

    This is your opportunity! If your largest use would only be 2gpm, then don’t plan on more than that. It’s like people who buy an SUV because “once in a while” they need to fit a lot of stuff, and then they use it to commute 50 miles a day by themselves.

    It seems like our American way of life is based on having what we want 100% of the time and forgetting about the environmental consequences. In most situations, it seems like people who give up a small amount of convenience save enormously (with money and the environment) in the end.

    Now is your chance to buy a system that meets your needs instead of the American standard!

  2. 2

    Linnea said,

    August 25, 2008 @ 11:46 pm

    I think I’ve brushed my teeth while someone else was showering or doing dishes (in the sink, no dishwasher). But that’s pretty rare, since I do most of my showering/teeth brushing pretty early in the morning. I don’t think your usage is unreasonable.

  3. 3

    Lori said,

    August 26, 2008 @ 9:56 am

    We have an old, but still functional, water heater. It produces much more hot water than we were used to, primarily because the previous owners installed a jacuzzi tub that we’ve used exactly twice in the two years we’ve lived in this house. We do occasionally do laundry and run the dishwasher at the same time, and we’ve had a few instances when we’ve needed to use both showers at the same time (generally only with houseguests). Honestly, if I have my druthers, we’ll downsize it a bit when it finally dies. As it is, our tank is large enough that we avoid the not-so-subtle reminder of cool showers to remind us that hot water doesn’t come free (to us or to the planet)…which is not necessarily a good thing.

    So I don’t think you’re being unreasonable. Good luck with your water bill!

  4. 4

    Susie said,

    August 26, 2008 @ 10:10 am

    I was amazed by the estimate you were given, so I went out and looked (Lowe’s), and water heater prices are just all over the place! And it seems like you could get a couple of tankless ones for the price of a large super-efficient tank one – or, you could get a smaller tank one for a lot less money. It’s hard to know how much installation would cost, but Lowe’s would probably have a list of people to call – unless the big selection on-line is not readily available here in Indiana…

  5. 5

    Fred said,

    August 26, 2008 @ 12:44 pm

    I encourage you take a look at http://www.ViridianTankless.com. Our company is manufacturing a new high-quality, whole-house electric tankless water that will surely impress you.

    Fred Huggins
    Sales & Marketing
    Noble Innovations, Inc.
    Phoenix, AZ

  6. 6

    Emily said,

    August 26, 2008 @ 5:31 pm

    Wow. We were trying to make this same decision, and a regular electric heater was $1300 and tankless was $3500. Does the electric tankless you looked at alo cover the same 55-degree temp differential? And does your water come in at 50 degrees? Because 105 degrees is not a nice warm shower when it comes out the sprayer…

  7. 7

    Will said,

    August 26, 2008 @ 6:13 pm

    Good point, Andy. Our biggest long-term concern is that if we have a kid and use cloth diapers, we’re going to want to be able to wash clothes in hot water. One of the good things about tankless is that even if we buy something more than we need right now, it won’t use much more electricity than a smaller one. Getting a 60-gallon tank when we only need 40 gallons (or less) is much worse.

    Thanks for the reassurance, Linnea and Lori! I’m glad to know that there are other households out there that don’t need a lot of hot water at once.

    Susie: We talked to the Lowe’s people earlier and they only have one electric water heater available that’ll fit in the crawl space (a 40-gallon low-boy). If I recall, it was about $350, but they’d charge $65 for someone to come out and inspect the crawlspace in addition to the installation fee.

    Fred: It looks interesting, but I don’t see anyone selling them yet. Do you have links to people selling them directly?

    Emily: That seems like a lot! A 40-gallon electric low-boy (which we need, because the crawlspace is low) runs $270-400. The estimate we got added on $400 for installation, which seemed high to us, although we haven’t gotten another estimate on that.

    The electric tankless we’ve looked at have been $900-1200. There are some cheap ($300) point-source ones, but we’d want at least three so it makes more sense to go whole-house, I think. I haven’t gotten an installation estimate, but the plumber I talked to said that it would be no harder to install a tankless electric than a tanked electric, so it shouldn’t be more than $400.

    The temperature differential depends entirely on flow rate. Bosch has a good one for about $1000 (the Powerstar AE-125) that will do a 50 degree rise at 3.7 gpm. However, at 2.2 gpm (about a shower’s worth), you’ll get a rise of 80 degrees (up to 131 degrees — it’s oddly specific about that).

    I’m not sure what our incoming water temperature is, so I’m not sure exactly how much of a temperature change we’d want. 80 degrees seems like more than enough, though!

  8. 8

    Andy said,

    August 26, 2008 @ 9:54 pm

    Even with higher needs (e.g. a kid) you wouldn’t need more gpm, just hot water more often. In either tank or tankless that doesn’t mean that you would need a larger system, it would just be on more frequently. More than 1/3 of my electric bill goes to water heating, so if I had the choice here I would go with a tiny tiny system that fit my basic needs and nothing more.

  9. 9

    Andy said,

    August 26, 2008 @ 11:03 pm

    BTW, I just got 20 peaches cut up and in my dryer. I paid $4 for the dryer at a Salvation Army store 2 years ago (best purchase there ever!) and I picked the peaches myself the other day a $10 for 21 pounds. I still want to make a solar dehydrator, since this one takes 265 watts continuously, and most things in it take around 8 hours although I haven’t done peaches before. That’s about 2kW right there, yikes!

  10. 10

    Will said,

    September 4, 2008 @ 3:35 pm

    Andy: We probably wouldn’t need much more gpm, but we might want higher temperatures (for washing dirty diapers) which reduces the output on a tankless water heater. We might also want to be able to wash clothes and take showers at the same time since we’ll be doing both more often. I think you’re right overall, though. Even if we vastly increase our water usage and temperature, we’d still be well within the abilities of an electric tankless water heater.

    Very cool! Just last night, Maggie brought back some of her dried peaches. It’s amazing how inefficient electricity is at heating!

  11. 11

    Less costs more | GreenCouple.com said,

    September 8, 2008 @ 11:20 pm

    […] several weeks of suspense, we got our water bill in the mail today. Over the past 37 days, we used 67,000 gallons of water. It turned out to be much better than we’d feared: about 1/3 the cost of our worst-case […]

  12. 12

    Jeff said,

    February 10, 2009 @ 8:20 pm

    Good luck however you make the decision, but kudos for the analysis. Be sure to check in the crawl space for mold since you’ve had water spraying in there from the leak.

  13. 13

    Will said,

    February 11, 2009 @ 11:36 pm

    Thanks! We’ll probably end up going with a traditional natural gas water heater (for reasons that I plan to write about soon).

    Our crawlspace apparently drains really well, since it was only mildly damp while the water was leaking and dried out entirely within a day or two after we fixed that. There wasn’t any evidence of mold when we checked earlier in the year and now it’s too cold for it, so I think we’re safe.

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