Comments on: Total Energy Efficiency Of The US

By: Some Interesting Energy Efficieny Statistics « PeakGlobalization.com

Some Interesting Energy Efficieny Statistics « PeakGlobalization.com — Tue, 07 Sep 2010 13:06:32 +0000

[...] Total Energy Efficiency Of The US [...]

By: US Economic Energy Efficiency 1950-2008 « True Cost – Analyzing our economy, government policy, and society through the lens of cost-benefit

Sat, 09 Jan 2010 20:56:02 +0000

[...] energy intensive industries overseas. Further decreases in energy intensity will have to come from actual increases in energy efficiency, and from an increase in the quantity and relative value of low-energy products like online [...]

By: praveenghanta

praveenghanta — Mon, 23 Nov 2009 21:11:10 +0000

David, thanks for your comment. I was actually using the green glow (as mentioned in the referenced Wikipedia article) as the theoretical 100% efficiency limit. The question really is, what percentage of electrical energy is converted into usable (within human viewing spectrum) light? It’s a very low percentage, regardless of how you measure it.

While lighting in wintertime does help heat a house, it’s an extremely inefficient form of heating, as the electrical energy was probably produced in a coal plant at 40% efficiency to begin with, and then suffered a line loss before it got to your house (versus 80% efficiency with a modern gas furnace). To add to this, the lighting heat is pure negative in summertime in many parts of the US, as I noted in my article.

As I noted above, lighting isn’t one of the main contributors to residential energy usage – even if we all switch to tube lights, we’ve got a ways to go on the energy efficiency march.

By: David Bronaugh

David Bronaugh — Mon, 23 Nov 2009 20:57:31 +0000

Your analysis of lighting efficiency is flawed. The maximum efficiency for an ideal white light source (as referenced in your wp article) is 37% — unless we’re all going to live by the 555nm green glow of an ideal radiator from the lumen perspective, that’s the efficiency limit. So fluorescent lights are 21% (for crappy CFLs) to 41% (for high-efficiency T8 tubes) efficient, and incandescent light bulbs are around 7% efficient for your average household lights.

Also, your assertion that waste heat from lighting increases home cooling loads is correct — but in winter, the waste heat from these lamps heats your home at least as efficiently as other forms of home heating (gas furnaces have a heat exchanger, which reduces their efficiency; light bulbs do not).

By: norhussein

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