The "incandescent makes useful heat"

[cardamon]

When consulting on energy conservation, one of the obvious things to suggest is changing lights to compact fluoros.  However there is a school of thought that argues the following:  "The heat from an incandescent bulb is not wasted but contributes to space heating, and this makes sense because heating with electricity is now cheaper than propane or fuel oil."  Comments on this?  A few of my thoughts:

1.  We are considering this arguement for a grid tied house, not off grid.
   
2.  We are considering this arguement for a location with a long heating season.  I am in central NY and we genrally need heat 8 months out of the year.
   
3.  The statement that it is cheaper to heat with resistance electricity than propanen or fuel oil is true (perhaps for not much longer if petroleum continues to fall).  I did the numbers a while back and if memory serves me correctly, propane at $3.30 a gallon is the even point if elec is .12/kwh
   
4.  How much benefit do we get from heating our ceilings?
   

[boB]

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Incandescents also work great for Chicken Coops.

boB

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[wooferhound]

I used incandescent bulbs to heat by bathroom a few years ago.

http://www.fieldlines.com/story/2004/2/8/183240/2517

[zeusmorg]

 There is truth in the statement the heat isn't wasted, unless you're a/c is on... Then you have to cool down the heat generated by them.

 The most efficient way to heat with electricity is with a ground loop heat pump. Compared to straight resistance heating you can use 65% less electricity (depending on conditions)

 As fas as comparing different fuels, it can get complicated. You need to know the fuel costs, efficiency of your furnace and most likely how long it would take to pay back newer equipment.

 So unless you are heating year round wouldn't it make more sense to convert to a lower lighting cost? Especially since if the light is at the ceiling, it wouldn't do much in the way of comfort. Also fluorescent fixtures at the ceiling can be insulated whereas one designed for incandescent only sometimes require an airspace to keep cool enough. (depends on the specific design of the fixture)  

 You could also use the same argument on other electric appliances that put off heat.

[Flux]

If you can feel the benefit of the heat then it is not wasted. I think boB's chicken coop is a very good example.The same may be true with lots of incandescent lighting in a small room.

In most rooms the 100W or so will have no measurable effect on the temperature so you might as well save 60W with low energy lighting if you can use the power for something else.

It's not a clear cut case but except for a few special cases the heat is probably worthless.

Flux

[spinningmagnets]

I'll bet there is some useful research on this over at "BuildItSolar.com" but there's so much info there it may take a while to find it.

In my humble opinion, most ceilings aren't as insulated as the average person might assume. In addition, to get the benefit of that incandescent heat, you must circulate the air with a ceiling fan. Will you switch to CFL's when the weather is no longer cold, and your A/C occasionally cycles?

Also, every energy conversion (electric-to-heat) involves losses. I am not against electric heat, it depends on the application, and your local cost between electric and propane/methane.

When the weather is colder than normal here, we turn the thermostat down some (central forced-air methane burner in the attic) so we're not heating up the entire house. We block off the two unused bedrooms (kids grown and gone) because even double-glass windows are heat sinks.

Then we have a small portable electric room heater the size of two loaves of bread (only heats the TV/computer room). It has a thermostat so it cycles on its own, and its basically a square hair dryer, a fan blowing on resistance coils.

In the bedroom we use an electric room radiator on the lowest setting that is oil-filled, and a slow ceiling fan. Timer only has heater on first half of night, room finally gets cold about time to wake up. Don't know which ideas helped the most, but monthly heat cost went down.

Went to CFL's for the 3/4ths of the lights that are frequently used, and electric bill noticeably went down. I recommend separating heat devices from light devices. Use only what you need, where and when needed. Insulate, seal leaks, cover/isolate heat sinks (glass windows).

Absolute best heat (when available) is solar heat. These look goofy, but "can" be stored in garage most of the year when not needed:

http://cache.gizmodo.com/assets/resources/2007/05/soda_can_heater.jpg

Found out black absorbs non-visible infrared light and converts to heat. I knew it worked, just didn't know why before...

[jonas302]

I use this same method with great results heating where you are at

As far as light bulbs go it very well might depend on the house in this old farm house there is not many fixtures so not much heat others maybe have a bunch of can lights that would put off some heat

My office in the shop stays pretty cozt right down to about 25 degrees with a bunch of computers and lights on

I have all cfls but they are on so little in the house they will never pay back the cost so it might also depend on how you use the lights

[dnix71]

If you convert from incadescent to cfl's then your house will be cooler in the winter, and you will have to spend more to heat it. That is the tradeoff. You might lose money on the deal if you heat with fossil fuels and fuel prices are high, and you don't run the a/c much in the summer.

Adding insulation is the fix. If you live in a climate where you actually need the heat from light bulbs in the winter to keep warm, then something is not right.

[scottsAI]

Cardamon,

Separate heating from lighting regardless of heating cost.

Air conditioning is more expensive per BTU than Heating.

Many much better solutions exist.

Using CFL will not make heating more expensive.

Add resistance heating with temperature control for a real system. Not an add hock system dependent on whether your lights are on or not.

Fuel adjustment cost on my electric tracks the oil prices, so wondering about the math that suggest resistance heating is cheaper than gas?

Max efficiency

A heat pump will use electrical power more efficiently than resistance heating. Here in Michigan a heat pump is great for spring, fall, most of the winter except about 2-4 weeks when temperature dips below 20F. Below 20F another source of heat is required.

Have fun,

Scott.

[jacobs]

Here's a fuel cost comparison calculator that I use that I'm sure would be helpful to you....http://www.eia.doe.gov/neic/experts/heatcalc.xls

With the present propane prices, electric heat is now less expensive for us, but be sure to factor in your furnace efficiency. If our new administration gets their way, electric rates will skyrocket with the proposed tax on our present coal fired power plants.

At present, we use compact flourescent bulbs in the summer and incandescent bulbs in the winter. It's better to use incandescent bulbs year around in locations that are frequently switched on and off like closets hallways, and stairs. Flourescent bulb life is drastically reduced by quickly switching them on and off. If you turn them on, leave them on for at least 15 minutes. Flourescent bulbs also work poorly in cold locations like garages, chicken coops, and outdoors.

[scottsAI]

Jacobs,

Thanks, nice sheet, where did you find it, looks familiar?

Numbers are in line with what I pay.

My gas cost for heating is less than half electric heating.

Nice 92% high efficiency furnace, using since 1986. Paid for itself years ago!

Have fun,

Scott.

[jacobs]

I found it last year ago while searching the internet looking for info of cost of BTU's of different fuels.

[richhagen]

For me, the cost of heating with natural gas is much less than with electricity.  Where I am one would still come out spending less money with compact flourescents for lighting and natural gas for heat given the current low prices for the compact flourescent bulbs.  In summer it is of course of even much better advantage to use the flourescents.  Still incandescents can make a nice small radiant heater for some applications.  When using electric heat anyway, I find that in my basement workshop, the radiant heat of an infrared bulb gives a better spread of the heat than some other types of space heaters that send all the heat up to the ceiling.  Rich

[cardamon]

Thanks for all the good replies.  Natural gas is unlikely to be more expensive to heat with than electric for some time, however propane and oil are more expensive than electric resistive in most parts of the country - well as of a few months ago.  With the significant drops in oetroleum prices, maybe not now.