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Comment by ericd | Hacker News Reader

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.

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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?

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...

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