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Comment by greenyoda | Hacker News Reader

"We already know that incandescent light-bulbs are on the way out because they're incredibly wasteful, being better at producing heat than light."

In climates like the northeast U.S., the heat that incandescent bulbs generate isn't wasted for most of the year: it helps heat your house, which means you burn slightly less oil or gas in your furnace. They're only wasteful during the summer months. And a CFL probably takes more energy to manufacture and recycle, and needs more packaging material to prevent breakage, since nobody likes to clean up toxic mercury spills. (After having read the dire warnings on the EPA's web site about what procedure to follow if you break a CFL, I never wanted buy another CFL again.)

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Incandescents release more mercury into the enviroment over the course of their lifetime because they use more electricity, since much electricity is based on coal mining (which inevitably releases some mercury). [1]

Also, if you're concerned about CFL taking more energy to manufacture and recycle, also consider the fact that a typical CFL lasts the lifetime of multiple incandescent bulbs.

(Note: I'm not trying to make any particular point other than the only valid way to compare two technogies is with a proper cradle to grave analysis)

[1] http://www.nrdc.org/legislation/files/lightbulbmercury.pdf

Interesting point, but that's mainly true if you use resistive electric heating. Heat pumps are much more efficient than turning electricity directly into heat unless it's extremely cold.

But if you're using both the light and the heat generated by the light bulb, aren't you making use of almost 100% of the energy that's being consumed?

Heat pumps actually move existing heat indoors, from outside, using electricity to do the mechanical work, so it's much more efficient than just using electricity to create heat directly.

More specifically, heat pumps often have a COP of around 2, even in very cold weather (-20℃). That means that for every two joules that a light bulb turns into heat, you will save only one joule (and less in most conditions) on your overall energy consumption.

In very, very cold areas, the COP of the heat pump will reduce to 1, and in those cases the incandescent bulb isn't wasting any energy.

Thanks for putting specific numbers to it. It's really surprisingly efficient, especially at warmer temps (0℃) which are more common in most of the US.

That number is also assuming that the pump pulls from the air rather than the ground. Ground based pumps are apparently more efficient (well, energy effective; efficient is not quite the right word in this case) because the ground warms up in the sun more than the air.

A heat pump can produce 2-5 times more heat than an electrical resistance heater (like an incandescent bulb). It pulls heat from the colder outdoor air with a pump, it sounds illogical until you study heat cycles... http://www.dbh.govt.nz/UserFiles/Image/Publications/building...

Last week I learned that x86 (and x86-64) PCs & servers are basically resistance heaters. So it's almost as efficient to heat your house by rackmount as it is by incandescent?

Haha electricity-wise, yeah, but you can get almost as much heat out of a 100W lightbulb as a $1,000 Xeon that's running at 100%, so you might be better off going that way if you're looking to save money :-)

OTOH, with Xeons you could sell virtual private server hosting to compensate for the heating expenses. Anyone care to make and ROI calculation here vs. resistive heating?

Look at it this way:

If electricity was cheaper than oil/gas, then you wouldn't use an oil/gas furnace to begin with.

So, an efficient lighting system is saving you money.

To second hrjet, think of it this way: electricity has to be produced from another source of primary energy, the efficiency of which is very much less than one. So even if electricity can be converted into heat 100% efficiently you are still better off producing heat from the primary source directly, ignoring the cost of distribution. In general the price you pay should reflect the utility of the resource consumed.

Yup, my house is heated using an electric furnace (resistive heat). Thus the heat from incandescent lightbulbs doesn't go to waste during the winter.

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