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posted by martyb on Tuesday February 12 2019, @09:17AM   Printer-friendly
from the read-this-while-having-a-nice,-hot-cup-of-tea dept.

Phys.org:

When you hear about businesses with a high environmental impact or activities with a high carbon footprint, you are probably more likely to imagine heavy machinery, engines and oil rather than hairdressing. Yet hairdressing, both as a sector and as an individual activity, can have a massive carbon footprint.

Hairdressing uses high levels of hot water, energy and chemicals. Similarly, in our homes, heating hot water is typically the most energy intensive activity. For the cost of a ten-minute shower that uses an electric immersion heater, you could leave a typical television on for 20 hours.

So while it helps to turn lights and appliances off, the real gains in terms of reducing energy usage are in slashing our use of hot water. A quarter of UK emissions are residential and, of those, the vast majority come from running hot water. The longer it runs and the hotter it is, the more energy intensive (and costly) it is.

Mostly the hot water used carries a high carbon footprint, but the chemicals in shampoo don't help either.


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  • (Score: 3, Insightful) by RS3 on Tuesday February 12 2019, @06:23PM (8 children)

    by RS3 (6367) on Tuesday February 12 2019, @06:23PM (#800210)

    Too many Popular Misconceptions out there (fake news, etc.) You mentioned "inefficient electric tank water heaters". I'm not sure why people believe that, other than salespeople trying to sell tankless units. Here's a great reference that compares efficiencies at the bottom of the page:

    https://www.fastwaterheater.com/water-heaters/articles/water-heater-energy-efficiency/ [fastwaterheater.com] (bottom of page)

    They did not list electric tankless (on-demand) units in the chart, but they talk about them in the article.

    I do NOT recommend electric tankless for general overall house hot water because yes, the unit itself is efficient; the problem is that there are losses in generation and transmission of electricity. On-demand tankless electric water heaters draw huge current. Most older houses need an overall electric panel & service entrance cable upgrade to use one. The higher the current drawn, the more resistive (I^2 x R) losses in all of the wires and transformers between the generator and your water heater. For that reason, you get charged more $ / kWh based on your peak demand. The web page I linked talks about these losses.

    The chart shows that electric tank-type water heaters are among the highest efficiency water heaters. Again, they didn't account for wire losses, but the peak demand is much less than on-demand ones. For example, most standard tank-type electric water heaters run on 240VAC through a 30 amp breaker (some are 40). On-demand tankless need 240VAC @ 60 - 120 amps (!!). (they run 2 or 3 40 amp circuits, NOT 1 120 amp).

    There are almost no losses in transmission of gas (pipes).

    Gas fueled tankless water heaters are much more efficient than gas fueled tank-types, but only because of inefficient designs of older tank units.

    So if you don't have gas available (or don't want it) go with high-efficiency tank (or hybrid) unit.

    If you have gas, go with a tankless (hybrid condensing is best).

    The best systems are hybrid and include geothermal and solar heat.

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  • (Score: 2) by maxwell demon on Tuesday February 12 2019, @08:30PM (5 children)

    by maxwell demon (1608) on Tuesday February 12 2019, @08:30PM (#800299) Journal

    There are almost no losses in transmission of gas (pipes).

    So how much energy does it take to transport enough gas through the pipe to get 1 kWh of energy?

    Also note that electricity is transported most of the distance on high-voltage wires, which means that the current is relatively low. So if at the house you have 120A on 240V, and the long-distance supply line is at 10kV, then the current on that supply line caused by your heater is merely 2.88A.

    I'd really like a to see a fair comparison between electricity and gas. With real data. Because all I've ever seen as arguments is based on very naive assumptions.

    --
    The Tao of math: The numbers you can count are not the real numbers.
    • (Score: 2) by RS3 on Tuesday February 12 2019, @08:47PM (4 children)

      by RS3 (6367) on Tuesday February 12 2019, @08:47PM (#800305)

      Did you click the link I gave and read the article I summarized?

      • (Score: 2) by maxwell demon on Tuesday February 12 2019, @09:05PM (3 children)

        by maxwell demon (1608) on Tuesday February 12 2019, @09:05PM (#800318) Journal

        A page by a seller of water heaters (certainly not an unbiased source) talking about money cost (not what I was talking about). In particular, it does not detail the energy cost (no matter what type of energy) that goes into transporting the energy to your house (that is, the very point I was talking about).

        --
        The Tao of math: The numbers you can count are not the real numbers.
        • (Score: 2) by RS3 on Tuesday February 12 2019, @10:32PM (2 children)

          by RS3 (6367) on Tuesday February 12 2019, @10:32PM (#800369)

          Okay, I spent some time and effort, did some research, posted a link to the best one I found which happens to agree with other references, the data looks good, makes sense, etc. It's an Angie's List award winner, in CA, the most energy-conscious and regulated state in the US (as far as I know and have heard). I don't see any reason for them to lie and lose their reputation, get sued, etc.

          You don't like it? Please do some research and post your results and I'll check back.

          • (Score: -1, Troll) by Anonymous Coward on Thursday February 14 2019, @01:16AM (1 child)

            by Anonymous Coward on Thursday February 14 2019, @01:16AM (#800815)

            > posted a link to the best one I found

            You found something in units (dollars) that aren't relevant. If it's $100 to kill a dog or $2000 to fly to Disneyland, do you kill the dog? His criticism - that your data isn't useful data to an environmentalist decision - is valid. You didn't give useful data. Stop whining. You posted "the best one [you] found" and it was bad. Do better or cede the point.

            • (Score: 2) by RS3 on Thursday February 14 2019, @04:12AM

              by RS3 (6367) on Thursday February 14 2019, @04:12AM (#800874)

              Who the hell are you? I owe you data? I owe anyone data? I spend time and effort to contribute here and you're whining about it? All you do is troll me whining about the data and link I gave, you give NOTHING but your troll? Go back under the bridge. Time for this site to eliminate ACs.

  • (Score: 0) by Anonymous Coward on Tuesday February 12 2019, @11:26PM (1 child)

    by Anonymous Coward on Tuesday February 12 2019, @11:26PM (#800388)

    You are only expanding on my proven point. The premise was that we need to revel in our own filth in order to satisfy the Green Nazis because heating water is such a horrible eco-disaster. TFS is clearly bullshit. I'm surprised they aren't railing about wasting water too. That's a common theme among the enviro-gestapo. The next step will be to have humanity huddling in a dark, unheated homes because banishing showers really wasn't our "most energy intensive" activity after all.

    • (Score: 2) by RS3 on Thursday February 14 2019, @04:19AM

      by RS3 (6367) on Thursday February 14 2019, @04:19AM (#800876)

      I have no idea if you're the same AC who trolled me, but you don't quite sound like him. You make really good points. My take, if I'm grasping the situation and if this is what you're saying, is that some people will never be happy. They seize a cause and go at it no matter what. They won't compromise nor listen to anything or anyone else. Egos are growing faster than anything else on earth.

      I forgot to add above: it's pretty easy to reclaim waste "gray water" heat- sinks, laundry, shower, etc., before sending it out to the sewer.