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Average Home Energy Consumption

Post in 'The Green Room' started by velvetfoot, Nov 20, 2012.

  1. TradEddie

    TradEddie Minister of Fire

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    I use gross energy, that's what I pay for, so any reduction is $ in my pocket. I'm pleased with our house, built in 1977 but with R13 in walls and R5 foam outside, much higher than typical of the time, although the foam may have been added later. Attic insulation is just okay, but having a cape minimizes that area anyway. On the other hand, the access doors behind knee walls were simply a particle board with 1/2" gap at the top, and there are still so many other air leaks that I'll never get them all. I know my house is still far from ideal so I think that the "average" number of 10BTU/HDD/SQFT is misleading because it doesn't account for different use patterns. Our propane heat is setback daytime Monday-Friday, or if we're off for the weekend, while others keep their home at 75F 24/7 all winter long.

    TE

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  2. jharkin

    jharkin Minister of Fire

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    Thats a good point. The 15 gross value at my place before we started insulating was also a time that my wife and I both worked full time and I had the heat setback to 62F daytime and 64 or 65 at night when asleep. Now we have two toddlers in the house and my wife is home full time the heat is at 68 all the time and i know she kicks it up to 70 a lot when I'm not home (when I am home the stove is lit :) ). So the improvement to 12 gross is probably even better than it looks.
  3. TradEddie

    TradEddie Minister of Fire

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    Beautiful house, paying a little more to heat something like that is a small price to pay. If you're counting wood in your gross calculation, then its not so bad either, since you're getting lower efficiency per gross BTU, and you're heating the house much more.
    I'm not out to save the earth or pinch pennies, but the less I spend on heating, the more I have for fun stuff.

    TE
  4. Slow1

    Slow1 Minister of Fire

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    So I ran my numbers and came up with something like 9Btu/HDD/sqft. I counted all household energy (electric, DHW heating, and wood). It seems odd to include the DHW and electric as these are not really directly heating related and the measurement is /HDD.

    In any case, with a family of 6 being below the average of 10 perhaps is a good thing - I don't know if that will hold as we start heating a bit more and thus consume more wood, but time will tell. Not to mention once the kids get old enough to start taking daily showers (or more often!?! I hear that teens today do?) and running up the DHW costs....
  5. jharkin

    jharkin Minister of Fire

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    That is wood included. And the reason I work out the net numbers is I wanted to very specifically check what differnece the insulation is making, normalizing out variations in how much of my heat Im getting from wood (72% eff) vs gas (83% eff) Last year we didn't burn much due to the weather and the kids, about 1 cord wood and 570 therms of gas to heat over a mild 4700 HDD winter. This year extrapolating Nov numbers across a more typical 5500 HDD winter I'm on track to burn about 2 cord and 450 therms.

    Overall I think its pretty darn good for this old place, I know our friends with old stone houses (BBar, Joful, Danno, etc) would probably kill for numbers so low...
  6. woodgeek

    woodgeek Minister of Fire

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    OF course when there are two ways of computing anything there are groups of people doing it both ways....but IMO, to characterize the insulation/tightness of your house envelope, I think you should use the 'net delivered BTU' for space heating, divided by the HDD (using your tstat setpoint as a base) divided by your conditioned square footage. I would call this a home heating index HHI.

    On these terms, I started at 12, and am now 6-7.

    This way, HHI doesn't depend on occupants, setbacks, or your fuel source and is a property of the house itself. If you crank the heat, your energy usage goes up, but your HHI doesn't.
  7. jharkin

    jharkin Minister of Fire

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    Wow there are a lot of ways to do this. Every article I can find talks about using the default 65 as the HDD basis - which is what I did. If I used the actual indoor temp of say 70 my numbers would be even better. I know that my house doesn't typically need any heat at all till the outside temps start falling into the 50s.

    Using 65 base HDD and net energy my usage has gone from 11.8 down to 9.7 with insulation improvements over 3 years.

    If I guess at the tstat set point and rework the numbers its probably more like 11.5 (with an average inside temp of 66) 3 years ago down to 8.2 last year (average inside temp close to 70)Even this is probably not quite right because I'm not figuring all the wood heat days where the average inside temp is more like 75 :)
    I'
  8. freddypd

    freddypd Burning Hunk

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    I have a ranch house about 2000 sq feet. 2x4 walls have been re insulated, attic insulation is not that great, windows replaced, vinyl siding with foam boards underneath.
    My wife really does try to keep the heat down, but I am ALWAYS cold so I usually bump it up. Now we are only running the bedroom zone at night at about 63-65. Living areas have been off since the new install of the wood insert!

    My furnace is probably circa 1998? Oil fired. My DHW is independent and fairly new.

    We have probably used 1/2 cord 4'x4'x4' so far this year. We do keep the room that the insert is in at 75-78! Like I said I am always cold.

    I want to get more efficient and save money. I have an insulation contractor coming Tuesday. I guess I will see what he has to offer.

    Thanks for the reply.
  9. Slow1

    Slow1 Minister of Fire

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    I suppose the real answer then depends on what the question is that one is asking? Your method would seem to answer the question of "how efficient is the house as a whole in terms of being able to retain/utilize the heating within." My question may be "Is my net energy usage on par with others in terms of a) total energy used in the home and b) total energy used considering the size of the home" Clearly each of these questions would require a slightly different calculation.

    For some the only question is "how can I further optimize for $'s" over some given period of time while perhaps maintaining some preferred level of comfort.

    At any rate, what I'm interested in knowing is more like the questions I asked as "my question" above - I really feel I've done a decent amount to reduce our overall energy consumption, but I'd like some objective measure on which to know if our household really is ahead of the curve in terms of energy use or not - yes, a bit competitive and likely meaningless but encouraging to me as I pursue further improvements.
  10. Seasoned Oak

    Seasoned Oak Minister of Fire

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    My wife sits around with a coat on at 75, we keep the kitchen and bath 77 LR 75 and BR 74 When the wood stove is going Floor 1 is 82 , Floor 2 is 77, Floor 3 is 74.
  11. DBoon

    DBoon Minister of Fire

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    Just calculated my BTU/HDD/Sqft.
    1250 square feet, 7500 HDD base 65, 89MBTU for heating, so 9.5 - considering it is a 1922 house, I guess I'm doing ok after all my insulation and weathersealing. I have a little more insulation to add in the attic....maybe I can get below 9 next year.
  12. woodgeek

    woodgeek Minister of Fire

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    I've got a link for that....

    https://www.energystar.gov/index.cfm?fuseaction=home_energy_yardstick.showgetstarted

    I don't really like this tool, but if I understand what it is doing, it computes your total site energy usage and then reports your percentile rank compared to other homes in your general area. I currently get a 7.3, which I think means that I use less site energy or produce less CO2 than 73% of homes in my area. I think it is probably a CO2 footprint score, and I would guess that it scales by conditioned floor space?? I could prob back out what it is doing by putting in different square footage, same BTUs of different fuels, etc, but I haven't bothered with that yet.

    But it is what you asked for: a single number score comparing you by some metric to your neighbors.
  13. jharkin

    jharkin Minister of Fire

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    Ug...I get a 2.8 on that tool.
  14. jebatty

    jebatty Minister of Fire

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    Calculation based on Mbtu/hdd/sqft for our house, base 65:

    Heat only (elec + wood) = 5.3
    Total energy usage = 7.5
  15. TradEddie

    TradEddie Minister of Fire

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    This could be a very nice tool, but completely wrong calculation numbers, so its hard to know if it means anything at all, 1 kw/h is 11 KBTU, 1 cord is 17.7MBTU?

    TE
  16. woodgeek

    woodgeek Minister of Fire

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    These numbers make sense....To make 1 kWh of electricity requires 11kBTU of fuel to be burned at the power plant, at something like 30% efficiency. 17.7MBTU sounds like a typical number for wood (low for hardwood, but not crazy)
  17. woodgeek

    woodgeek Minister of Fire

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    Ok. I played with the yardstick site. It appears to rank you on total primary BTU (not site), compared to households in your area with the same square footage and number of persons. It reports CO2, but does not appear to factor that in.
  18. TradEddie

    TradEddie Minister of Fire

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    I see, thanks for the explanation, I would never have thought of that. So now I can feel proud of my score, although grading on the curve of average homes in the Philly suburbs isn't exactly a high standard. One of the many flaws in any such comparison, but nonetheless useful.

    TE
  19. Slow1

    Slow1 Minister of Fire

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    I tried it and ended up in the 9.3 range, but if it is going with "primary" energy that means it is considering the electric cost higher as they assume loss due to transmission etc, right? If that is the case someone running on solar should be able to indicate that is it would make a material difference, wouldn't it?
  20. woodgeek

    woodgeek Minister of Fire

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    What's your score??
  21. TradEddie

    TradEddie Minister of Fire

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    If you're feeling really geeky, you can see the distribution curve for the inputted home by viewing the HTML source code...
    If you have solar, just don't enter the solar kWh.

    Either way 9.3 is very impressive based on what I saw with the distribution, you listed your BTU/HDD/SQFT earlier, what were the numbers that went into that?

    TE
  22. TradEddie

    TradEddie Minister of Fire

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    7.3, without correcting for using only hardwoods. 1 cord wood use is an estimate/aspiration now that I've switched from a slammer insert to an EPA model. 2 cords was typical for previous years, which comes out at 6.3. Based on what I see so far, I may end up using similar quantity of wood, but much less propane, which won't help my score, but will help my pocket.

    I'm also expecting improvement this year after completing multi-year widow sash replacement project, massive air-sealing mission, insulating rim joists, and recent block-off plate installation. Last year's record mild winter prevented me seeing if any of that work was visibly worthwhile. With the imminent end of PECO off-peak electricity, next step is probably an on-demand water heater.

    TE
  23. woodgeek

    woodgeek Minister of Fire

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    Nice. Got it. Found my score vs MBTU and dumped into excel. But then I realized that it is only for my 'matched home' in my area. Anyway faster than putting in a bunch of numbers!

    If I derate the 50% wind power I buy as 1 kWh = 3400 BTU, then my primary drops to ~120 MBTU and my score goes up to 9.3. If I bought all wind power (or hydro) I would get to 9.9 out of 10.
  24. Slow1

    Slow1 Minister of Fire

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    Ok - I updated my numbers as I now have my Nov elec usage (it was ommitted last time) so taking my last 11 months of usage and extrapolating it to 12 months I get an annual rate of 4,939Kwh, then 220 gallons of oil (my DHW mostly, a bit of heating as well), and then 3.5 cords of wood (high end of my average). I put in 2500sqft even though we have a bit more than this and we really don't use the basement for anything other than storage. We have 6 in the house. So with these numbers I end up with a 9.2 (10MtCo2Equiv). Now, if I do as you suggest and take the electric to 0 (solar generated, we have had a net over-production in the last year, maybe I should put in a negative number? ha!) then I end up at 9.9 (9MtCo2Equiv).

    A couple other interesting points - it seems they do calculate fractional parts of cords as even though it displays 3.5 as 4 in the report, when I put in 4 cords it makes a difference in the end result. Also it would seem helpful if they would put a bit higher precision on the MtCO2Equiv as going from 10 to 9 doesn't really seem to be all that much of a difference and I suspect there is some rounding there.

    All in all an interesting diversion I suppose, not sure it will change any actions. Their suggestions are clearly not tailored to the results as their suggestions are all very generic.
  25. TradEddie

    TradEddie Minister of Fire

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    5000kWH for 6 people is impressive, doing at all solar is even more so.

    That tool counts wood as full CO2 emission, which is not fair. However, I have to credit it for showing me how much my electricity usage contributes to my carbon footprint, I knew it in the abstract, but hadn't realized how much, I would have expected my propane to be a much higher proportion.

    Not that I'll do anything about it, I'm a terrible hypocrite when it comes to climate change, I'll conserve to save money, but at present I'm not prepared to pay anything extra for wind or hydro when the majority of the population is making no effort whatsoever to reduce CO2. That's why I favor a carbon tax, to kick my ass into gear, and 200 million others at the same time.

    TE

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