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Home energy usage

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Zman
Zman Member Posts: 7,605

I am attempting to estimate total home energy use for a code-required calculation and it is more challenging than I expected. The Heat loss calc part combined with HDD seems pretty straightforward. The DOE estimates that the average household uses ~64 gallons of hot water per day. I suppose I can just plug that number in but it does seem a bit low. What about all the other energy uses in the house? It will have LED lights and Energy Star appliances so I expect the number to be fairly low. The actual usage is a wildcard. In this case, the home will be occupied with 4 people, 2 being young children.

Does anyone have any resources to share? The AJH has offered a spreadsheet that shows 77 kBTU per sq foot which seems ludicrous. They are amenable to alternate calculations, I am having trouble finding good options.

"If you can't explain it simply, you don't understand it well enough"
Albert Einstein

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  • Jamie Hall
    Jamie Hall Member Posts: 23,635
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    This is new construction? Don't know of any general info, but for what it's worth Cedric's home uses 30 kWh per day of electricity, and is sort of average in terms of appliances and lights…

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Zman
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,387
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    Hi, The rule of thumb for hot water use is 20 gallons for the first person and 15 gallons for each subsequent person. In real life it can vary by an order of magnitude 🤪, but it's quite close to your 64 gallons 😎

    Yours, Larry

    Zman
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
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    129,000 kWh a year is laughable. I wish I had a better resource for you, but I average 833 kWh a month in an all electric house without really trying.

    Zman
  • Zman
    Zman Member Posts: 7,605
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    Thanks for the response. What region are you in? I expect the number to be a little higher in Zone 7 and 10,000 HDD but still can't get near their number. Not to mention, this house is really tight and well-insulated!

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • hot_rod
    hot_rod Member Posts: 22,472
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    did you try NREL, they seem to have a lot of calculation formulas and are close to you.

    I use 20 gallons for the first, 10 for additional users.

    The IAMPO Wdc is a good calculator for DHW and the AHJs should accept those numbers.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Larry Weingarten
  • Jamie Hall
    Jamie Hall Member Posts: 23,635
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    I mssed that 129,000 kWh per year (the type was too small).

    That's just nuts. I'd expect a tenth of that — if that.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Zman
    Zman Member Posts: 7,605
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    So far what I have for lighting and misc is 11,950 KW (this is a serious SWAG), For DHW I am at 5,256KW, and Heating at (10,00 HDD) 24,648 KW. The heating design day is 11.7 BTU/sq ft.

    I am very comfortable with the heating and DHW numbers. I don't like having that big of a SWAG on the other.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Zman
    Zman Member Posts: 7,605
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    I use NREL's PVWAtts regularly. I haven't found anything useful for the rest yet.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
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    Thanks for the response. What region are you in? I expect the number to be a little higher in Zone 7 and 10,000 HDD but still can't get near their number. Not to mention, this house is really tight and well-insulated!

    Smaller and warmer but still. 4000 HDD65 or so in a century plus old house with a 18kbtu/h heat loss. This is using a heat pump I assume?

  • DCContrarian
    DCContrarian Member Posts: 301
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    I pay over 25 cents a kWh. 129,000 would be over $30K a year. I think I would notice that.