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Electric resistance heating

Post in 'The Green Room' started by Ehouse, Mar 29, 2012.

  1. Highbeam

    Highbeam Minister of Fire

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    Nope, a watt is a watt. The feeling that you are saving money with the space heaters is false. What's likely happening is that you are closer to the portable so you feel warmer and the rest of the house is colder. If you are spending less money on electric then you are not heating to the same level. ALL electric resistance heaters are 100% efficient. The sooner we all get convinced of that the better.

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  2. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

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    You keep saying 15,000 watt and BTU oil filled rads. There are no such animals. They are 1500 watt 5120 BTU heaters.
  3. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    A watt is a watt of course and a BTU is a BTU but heat flow may put less actual heat in the room in one case vs the other.

    Let's see who can figure this statement out, get out your slide rules and start calculating (no hints will be given).
  4. Ehouse

    Ehouse Minister of Fire

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    I stand corrected, 1500 watts it is.

    Ehouse
  5. Ehouse

    Ehouse Minister of Fire

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    I think the bear has nailed it. 6' of baseboard puts out 1,500 watts = 5120 btu's., same as the oil filled space heater. But it transfers it's heat by convection (mostly) whereas the space heater has a larger radiant MO. It's the same idea as a masonry heater using a lot less wood to achieve comfortable (not necessarily equal air temp.) conditions. A watt is a watt. Yes, and you can't get any better than 100% efficient, but the processes used to make the electricity are not at 100% by any means, nor are the processes used to transfer the heat to our bodies. If a radiator can make me feel equally warm with less watts than a convector, that will show up on my bill as a cost savings.

    Ehouse
  6. Highbeam

    Highbeam Minister of Fire

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    base of Mt. Rainier on the wet side, WA
    If you're the type that can hold your finger above a candle flame and your whole body gets hot then yes, you can save money on house heating.
  7. begreen

    begreen Mooderator Staff Member

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    Technically you can get better than 100%, with an efficient electric heatpump. In our area they are much more efficient than baseboard or space heaters.
  8. DickRussell

    DickRussell Burning Hunk

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    Mar 1, 2011
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    Loc:
    central NH
    Others have covered the basics before. The energy required to keep a house at a given temperature equals the total heat loss through the outer shell, including the basement slab. A good energy model adds up the heat losses through each part of the shell, windows, doors, walls, upstairs ceiling, basement walls and slab. Steady state heat transfer through any part of the shell is proportional to temperature difference between inside that part and what's outside that part (outside air or ground at whatever temperature). Keeping part of a house cooler reduces heat loss through that part. Spot heating can heat occupied areas while leaving the rest of he house cooler to save energy.

    A slab that provides heat to the room volume above it must be well insulated below to minimize heat loss to the ground. This often is not optimized, with just a 2" foam layer under the slab. In a heating climate, a heated slab really ought to have at least 4" under it, with thermal isolation of slab edges from the foundation walls.

    As I've said before, first costs for a new house in a heating climate ought to be spent on the outer shell, going in the direction of superinsulation. Done at build time, it adds very little to the cost of the house but pays off in relatively few years in sharply reduced heating costs and also providing notably more comfort inside.

    In my case, we are finishing up the first year in our new superinsulated house. It's in central NH and has a footprint of 2,000 sq.ft. and has two levels, the lower of which is half buried in the ground (it's on a hill). We have a ground source heat pump and use it to keep the upper level at 70 and the lower level at 67. It's only a two-ton, two-stage heat pump, but it has kept the house at temperature without needing to go to second stage. Of course, the winter wasn't all that bad this year, with only a few nights down at zero or thereabouts. I don't have proper instrumentation on the heat pump to measure cumulative electric power use, so I can only infer heating cost from monthly electric bills vs bills for shoulder seasons when no heating or cooling is required. For the period mid-November to mid-March (5 months), and adding a bit for late October and April, the total heating season cost for this (abnormal) year will have come to about $500 or less. [Edit:] I should mention that the rough cost to go superinsulation vs "ordinary construction" for this house was around $20K, about the cost of a new car. Simple payout is around 10 years or less. We have hardly used the woodstove, although that can heat the whole house. It's a Quadrafire 2100 Millenium, fire range of 11-38K BTU/hr.

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