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electric heater efficiency

Discussion in 'Home Power and Microgeneration' started by james, Nov 26, 2010.

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  1. james

    james Guest

    Saw an ad for energy efficient heater, which prompted this question:

    Aren't all electrical heater equally efficient in converting electricity to
    heat?

    If not, where do the lost energy go? Don't they all get converted to heat
    sooner or later?

    The only way I can think of to consume electricity and not generate heat is
    to radiate off the energy as electromagnetic wave (radio wave, x-ray, etc)
    which can radiate away into infinity and not generate heat.
     
  2. vaughn

    vaughn Guest

    Yes, all resistance electric heaters are equally inefficient at converting
    Watt-hours to BTUs. Some heaters may be better than others at putting those
    BTUs where the people are in the room.
    There are some heaters that are being marketed with a generous dose of snake
    oil. I actually had some respect for Bob Vila before he hitched his name to
    one.

    The only electric heaters out there that can save any significant amount of
    electricity are heat pumps.

    Vaughn
     
  3. Josepi

    Josepi Guest

    We went through this wave of "Microfurnace" comes to mind years ago. The
    ceramic heater and high-efficiency crap. It's all CRAP.

    The Canadian Consumer and Corporate Affairs got involved last time and
    deemed them the same efficiency.

    Now if you get a graduated heater that can put out only the heat desired and
    not cycle on and off for heat waves then you may save 1 or 2% or just be
    more comfortable.

    Careful about the ceramic puck heaters. We had one short out internally and
    shoot flames out of the front. On a carpet it could be disasterous.

    Save your money to buy a magnetic water softener...ROFLMFAO. We need bigger
    prisons.


    Saw an ad for energy efficient heater, which prompted this question:

    Aren't all electrical heater equally efficient in converting electricity to
    heat?

    If not, where do the lost energy go? Don't they all get converted to heat
    sooner or later?

    The only way I can think of to consume electricity and not generate heat is
    to radiate off the energy as electromagnetic wave (radio wave, x-ray, etc)
    which can radiate away into infinity and not generate heat.
     
  4. Jim Rojas

    Jim Rojas Guest

    I live in Florida. To save money, I use the oil filled plug in heaters
    that you can buy at Walmart. I set it on #3 setting, and use only the
    lower element. It keeps the room nice and cozy. My central air heat pump
    just uses too much power. There is no need to heat up rooms no one
    sleeps in.

    Jim Rojas
     
  5. Josepi

    Josepi Guest

    That makes sense for your climate and in general but the oil filled is only
    a comfort feature and doesn't save money, especially vs. a heat pump with a
    3:1 COP or better.

    Need some zone controls there, and/or more thermal mass to carry heat
    overnight and cool over the day. One guy here put up large pipes full of
    water to stretch the heat periods longer (desert type climates profit well
    from this stuff)



    I live in Florida. To save money, I use the oil filled plug in heaters
    that you can buy at Walmart. I set it on #3 setting, and use only the
    lower element. It keeps the room nice and cozy. My central air heat pump
    just uses too much power. There is no need to heat up rooms no one
    sleeps in.

    Jim Rojas
     
  6. Jim Rojas

    Jim Rojas Guest

    That would be ideal for new homes. My house was built in 1964. It
    originally didn't even have central air.

    When we remodeled the house, we installed 3 inch foil backed sytrofoam
    in the attic, followed with R34 a year later. Before we did the stucco
    finish on the concrete block, they drilled 1/2 inch holes every foot all
    around the house. Then they injected expanding foam into the nterior
    walls. It cost us $2500 to do this, and we got a 1500 rebate from our
    utility company. All our windows are double insulated.

    In the summer months the AC runs for very short periods of time to keep
    the house at 76-78 degrees.

    Jim Rojas
     
  7. Gordon

    Gordon Guest

    The fan uses some electricity that isn't converted to heat.
    But it is a very small amount.
    But, when the radio wave is absorbed by an object, it heats it.
    CF: A microwave oven.
     
  8. vaughn

    vaughn Guest

    Also in Florida, we installed a mini-split reverse cycle AC in our bedroom.
    Winter or summer, that is the only nighttime AC or heat running in our house. It
    is more efficient than our (older) central unit, and so quiet it's hard to tell
    when it's running. If we weren't empty nesting, I would do the same with the
    other bedrooms. In the daytime, the bedroom doors are closed and the central AC
    vents to them are closed off. There is no need to heat or cool empty rooms.

    Vaughn
     
  9. vaughn

    vaughn Guest

    We figured that out the hard way when we tried to cool our bedroom with one of
    those one-hose portable AC units. The problem was, for every cubic foot of hot
    air that box blew out of the house, another cubic foot of saturated Florida
    mugginess infiltrated from outside. The result? Cool and uncomfortable. Never
    use a one-hose portable AC in a high-humidity area! We sent that one to my
    daughter in California. There, it works great.

    Vaughn
     
  10. Curbie

    Curbie Guest

    Why doesn't the electricity the fan uses convert to heat?

    Curbie
     
  11. Curbie

    Curbie Guest

    That was my understanding that electricity was about 100% efficient,
    and Natural Gas, Fuel Oil, and Wood were all about 80% efficient.

    Curbie
     
  12. Bob F

    Bob F Guest

    There is no need to heat the room I sleep in here in Seattle. I've got 3
    comforters which keep me toasty all night with the house as low as 45F. The bed
    room is the last one I'd heat, except for certain special occasions. A standard
    space heater takes care of those just fine, and warms up the bed in 2 minutes if
    needed when I climb in.
     
  13. Jim Rojas

    Jim Rojas Guest

    45 degrees? Ouch. My tropical fish would have a cow. I do have heaters
    in my fish tanks, but damn.

    Here in Florida when it hits 60 degrees all my neighbors break out the
    Alaska winter gear. They wear ski jackets, parkas, gloves, knitted hats,
    and scarfs.

    I was born in New York City. I wear shorts & short sleeve polo shirts no
    matter how cold it gets here. Last year it hit 25 degrees a few times.

    Jim Rojas
     
  14. Jim Rojas

    Jim Rojas Guest

    45 degrees? Ouch. My tropical fish would have a cow. I do have heaters
    in my fish tanks, but damn.

    Here in Florida when it hits 60 degrees all my neighbors break out the
    Alaska winter gear. They wear ski jackets, parkas, gloves, knitted hats,
    and scarfs.

    I was born in New York City. I wear shorts & short sleeve polo shirts no
    matter how cold it gets here. Last year it hit 25 degrees a few times.

    Jim Rojas
     
  15. vaughn

    vaughn Guest

    The statement above, while technically true, is terribly misleading. Saying
    that electricity is "100% efficient" ignores the huge losses involved in
    generating it and distributing it. It especially ignores the fact BTUs directly
    produced from electricity are typically damn expensive! In truth, almost any
    heating method is cheaper and more efficient than electrical resistance heating.

    No need to take my word for it; check your local energy prices and do the math!
    Convert everthing to cost/BTU to put everything on an apples-to-apples basis,
    and then factor in the efficiency of your furnace to get your true price. The
    conversions you will need are below

    Electricity: 3,413 btu per kilowatt-hour,
    Gas: 1 Therm = 1,000,000 BTU, 1 cubic foot = 1020 BTU

    Fuel oil/Diesel: 138,690

    Propane/LPG: 95,475 BTU/Gallon (100#=22 Gal.)

    Wood: 18 to 24 million BTU per standard cord (1 ton = 9 to 17 million BTU)

    Coal: 16 to 26 million BTU/ton

    As you can see, wood is the toughest to figure because the heat varies greatly
    with the quality of the wood, and there are too many differing definitions of
    what constitutes a cord. Of course, if you get it for free...



    Vaughn
     
  16. Maybe to those folk who write Congressional impact
    statements... but to the rest of us a therm is 100,000 BTU

    "Therm - One therm equals 100,000 Btu. " [a]

    [a] http://www.eia.doe.gov/ask/ng_faqs.asp#ng_conversions

    (and for the purposes of discussion, a therm can be
    taken as being equal to a "ccf", aka a hundred cubic
    feet of natural gas).

    (what's a typo among friends?)
     
  17. The problem of cutting wood is most tend to do it all at once instead of
    a little at a time all year. We used to
    cut mostly deadfalls when we had time and stack em up.

    I haven't cut a tree in years though, there's an industrial park around
    the corner that throws out enough pallets,
    offcuts and crates to heat an arena. I used the offcuts from a cabinet
    shop to heat my place for five years, all kiln
    dried oak, maple,hickory and cherry, usually 1 x 4 x 4-8" long. There
    was never any creosote build up in the pipes
    from that stuff ;~)
     
  18. Curbie

    Curbie Guest

    Jim,

    So you think 60-65% would be a reasonable efficiency number for
    estimations in wood stove planning?

    Curbie
     
  19. Curbie

    Curbie Guest

    Vaughn,

    Even though the post I was responding to was about the efficiency of
    converting electricity to heat, I think it's a valuable reminder that
    there are also costs involved with production and transportation of
    energy, but it in an "apples to apples" comparison, we would also have
    to consider those costs for natural gas, propane, fuel oil and wood,
    not just electricity.

    You posted some good information which I agree with the exception the
    issue Danny Burstein already pointed out.

    Thank,

    Curbie
     
  20. vaughn

    vaughn Guest

    Exactly. My conversion factors are worth what you paid for them, perhaps less.
    Check, check, check.

    Vaughn
     
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