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Old 02-21-13, 10:03 AM   #1
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Default Electric resistance heat efficiency?

Is there any real difference in efficiency of types of electric resistance heaters for on demand zone heating a room?

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Old 02-21-13, 02:40 PM   #2
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Nope. All electric resistance type heaters are 100% efficient.
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Old 02-21-13, 03:56 PM   #3
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I agree with Daox,

All resistance heaters have a COP of 1.00 by definition. This would include any device that asserts it is an infrared high efficiency heater ("Amish Heaters"). One kW = 3415 BTU. And if each kW costs ten cents ($0.10 - about the national average, $1 gets you ~34,000 BTU.

Sadly, some assert that resistant heat is 100% efficient compared to a high efficiency gas furnace ~94% efficiency. What they do NOT tell you is the energy cost of the fuel.

The above calculation, which gives you the cost of heat per $ of fuel is the best way I know of comparing apples to apples.

If a heat pump has a COP (coefficient of performance) of 4, then for each $ of electricity cost (@$0.10) would be 136,000 BTU/$. This is why heat pumps work so well.

Incandescent light bulbs are essentially resistance heaters as ~ 90%+ of the electrical energy goes to create heat.

By contrast, LED bulbs have the opposite (higher) efficiency with very little heat and lots of light (~90%).

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Old 02-21-13, 04:56 PM   #4
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Thanks, that is what I believed but marketing people can really get you to question what you think you know.
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Old 02-21-13, 08:20 PM   #5
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Incidentally, even with incandescent bulbs, aside from the small amount of light that escapes from your windows, the entire amount of energy that is emitted as visible light (that is the missing 5% when we say they are 95% heat emitters) almost immediately is converted to heat energy after it strikes an object and is absorbed. The re-release of excess energy in the struck object will be--ta ta, long-wave, i.e. heat radiation. So even incandescent lights are 100% efficient--all but window light leakage is almost immediately released as heat.

So also it is with the LEDs. If an LED is 5 watts, that is the amount of heat it ultimately contributes to your heat budget, except for leaked visible light. Of course, your windows leak long-wave radiation as well...

This logic continues to virtually all of your electrical usage with the exception perhaps of your wireless router--your washing machine contributes the wattage almost entirely as heat into your house. Of course your electric range, and your refrigerator and TV do, too. In effect, in each case it is energy being released into an almost closed system, except that portion which leaks out of the enclosure. So if you add organized energy (electricity) to your house, it eventually shows up in its disorganized form--as heat.
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Old 02-25-13, 02:00 PM   #6
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Reflector incandescent lamps make great heaters. The actual amount of heat coming off is about the same as other incandescents, but it feels much more intense because it's focused. Use a dimmer and you'll be able to control the heat as well as prolong the service life.
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Old 02-25-13, 02:09 PM   #7
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I disagree that all electric heaters are the same.
infrared heat will make you feel warm with fewer watts being used, that is why infrared heaters are used for keeping people warm in out door seating, in large poll buildings and even in large stores, they don't care as much about heating the air as they do about heating the people and objects.
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Old 03-12-13, 11:22 AM   #8
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Yep, they all produce the same amount of heat from the same amount of power.

The difference is how the heat is delivered. Conductive heat, like from a stove top, is best if you are in direct contact like a pan on a stove top. Most of us don't snuggle up to a stove.

So Convection (even with forced air) is normally moving the air past the heating element, and then you get heated from the air.

There is also radiant heating, like infrared heaters use. Yes, they warm up, but you sense the heat more directly without heating the air between you and the heater as much. This is what 'heat lamps' are.

The latest rage are 'heat pumps', where you use the energy to get, say a SEER of 10, is supposedly efficient enough to 'collect' 10 watts of heat for every 1 watt it uses, and allows you to re-deposit the heat elsewhere. ... This is basically a refrigerated HVAC unit in reverse. ... This is also why 'heat pump' water heaters cool the room where they are located. So if you use them, putting heat pump water heaters in your conditioned space makes sense to me (but that could be argued differently too).

I hope that helps.
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Old 03-12-13, 01:49 PM   #9
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My 20 year old propane water heater gave out last summer and I went shopping for water heaters. The propane models were predicting 513$/ year energy costs while conventional electrics were I think 508$/yr. Then i spied the heat pump type. estimated energy cost 295$/yr. The purchase price was around 400$ more but that's a 2 yr payback. When we got it home my wife looked and found that our electric company was giving a 350$ rebate! It works fine and seems to keep up with my 4 person household. Since it takes heat out of the room air and it is located in the same room as the furnace/air conditioner I cut a hole in the return ducting so the a/c when running would suck cool air out of the utility room and distribute it throughout the house. I only run it on heat pump mode during the summer cooling months, in the winter I run on conventional electric resistance mode. My theory is that the heat i take out of the air to heat my water needs to be replaced by heat from my propane furnace.
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Old 03-12-13, 02:01 PM   #10
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All electric heater generate the same amount of heat.

However, the thermostat governing the heater might make a sensible difference. Older mechanical thermostat might increase the heating cost by 15% and sometime much more depending on the characteristic of the enclose area. Furthermore, the comfort is much less generally.

Unit without FAN also permit a High quality electronic thermostat to make the room much more comfortable by keeping the heat element at a lower "Average temperature". What it means is that the heater is generally warm to the touch -- instead of being scorching hot.

I am in Quebec (where over 73% of the heating is by baseboard heating), so these type of thermostat are available at any hardware store (probably 10 brand of them). Elsewhere in US, I was able to find some of the HONEYWELL TH1xx series.

In any case, read the instruction carefully: You might need to inform the thermostat of the presence of a motorized FAN. Some assume the FAN exist -- and go ON/OFF by default -- these are not as comfortable. Some assume NOFAN -- and go proportional by default -- those will kill a fan motor on short order if you fail to reprogram them.

Actually, Honeywell did purchase a Quebec company call AUBE... You might get almost all model from their line-up under the HONEYWELL brand name -- Visit Aube Technologies inc. for more information

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