Comments on: Why Edison-style light bulbs aren’t always bad

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By: Jeff Chan

Jeff Chan — Mon, 22 Sep 2008 01:32:51 +0000

“Are we releasing more greenhouse gas emissions by using more fossil-fuelled heating to make up for the heat that we’re not getting from CFLs and LEDs?” – NO we are not – atleast for LED’s.
I’ve personally spoken to Energy Efficiency engineers here in Southern California – and there IS a way to calculate the BTU’s reduced by switching from incandescent to LED – and thus the amount of heat reduction – but it’s a complicated calculation – taking into account the many systems in place and the volume of air in the room etc. They said a general rule of thumb is that for every kWh saved, you can add about 20% to this, to account for the reduction in cooling costs. In hotter places like Hawaii – this maybe closer to 30-35%. So for example:

Incandescent bulb: 85W
LED Bulb: 12W
Over 50,000 hours – 85W-12W = 73W saved per hour.
73W x 50,000 hours = 3,650,000 Watt Hours
Divide by 1000 = 3650 kWh SAVED
20% of 3650 = 730 kWh saved in Air Conditioning
Total kWh = 4380
1.55 pounds of CO2/kWh x 4380 = 6789 lbs of CO2 reduced by switching 1 bulb to an LED.

In general – if you figure that replacing 1 bulb will save about 73W per bulb. Replace 20 bulbs and you’re saving 1460W per hour. This is typically how much energy a normal size air conditioner uses.

Here’s a link to the said bulb: 12W LED Light Bulb

By: Anonymous

Anonymous — Mon, 24 Mar 2008 19:28:28 +0000

Expanding on EMartin’s point back at Tue 18 Mar 2008 10:49 AM EDT:

In Seattle we have wonderful hydroelectric power sources, making 80% of our power carbon-free. However, hydroelectric power is very valuable for it’s quick availability and every bit we don’t use is sent down to California. What California can’t buy from us comes from coal plants back east. What this means is that when I switch on a 100W light bulb, then sure I’m getting much of this 100W carbon free. However, California now has to pull 100W it was getting from Washington from a coal plant somewhere east.

Because hydroelectric is more or less built out, and since nobody in the US has built a nuclear plant in over 30 years, and because all renewable energy sources are run full-out as often as possible, every bit of saved energy is saved from a fossil fuel power plant somewhere on the continent.

This leads back to the light bulb question. Your 100% efficient light bulb is using about 140% of the energy that makes it to you via a coal plant somewhere on the continent. It’s then leaking quite a bit of energy out your windows in the form of light, and much of its heat is leaking into your ceiling plenum and out your roof. Yes, you’re saving some heat energy, but natural gas has far less of a carbon impact and even heating oil beats coal. If you’re convinced electric is the way to go (which I agree with you in the long term, if we change our source energy), then invest in a heat pump. You’ll use about a third of the electric energy as resistance heat.

-Matt the Engineer

By: Anonymous

Anonymous — Thu, 20 Mar 2008 13:49:05 +0000

Ah nice to have an LCA from a European perspective. There’s another one from an Australian perspective here:

http://www.eeca.govt.nz/eeca-library/products/lighting/fact-sheet/environmental-impact-of-cfls-07.pdf

I’d greatly appreciate it if anyone is aware of other LCAs for CFLs or indeed any energy saving device. They appear to be few and far between (at least in the public domain anyway).

By: Anonymous

Anonymous — Thu, 20 Mar 2008 03:06:58 +0000

While it may be true that industry uses 89% of the water used in Canada, individuals can dramatically reduce that percentage by reducing their consumption! While there would still be a lot of room for improvement left for industry, individuals can still have a significant effect.

By: Anonymous

Anonymous — Wed, 19 Mar 2008 03:19:48 +0000

At a large international retailer, I watched the electricians sorting boxes of dead cfl’s. Each one had a date written in magic marker on the base. He told me that they had arranged with the supplier that any that burnt before their advertised life were replaced free of charge. Each new bulb they socketed also carried its fresh date with it up the ladder.

We have to change how we do things too, it cannot be solely a techno fix, and we must engage actively with the world around us. Reduce waste, then conserve what we don’t need to use, then use but do so efficiently, then source renewables. If we work all these at once we possibly can heat our homes with the old tube radio, filament bulb (radiation) and 286 computer, but not without first applying the same criteria hierarchy against the house itself, while standing up to suppliers as this retailer does.

By: Anonymous

Anonymous — Wed, 19 Mar 2008 02:35:14 +0000

I’m always greatful for a cheap shot. Or, preferably, an entirely free one. Those things can be expensive.

By: Anonymous

Anonymous — Tue, 18 Mar 2008 18:23:32 +0000

Thanks for the link — informative.

Now, I’m not so thankful for the cheap shot.

By: Anonymous

Anonymous — Tue, 18 Mar 2008 18:18:27 +0000

Jeeze, first you get suckered by a perpetual motion device and now this. Please learn what entropy is.
Ben Kenney recently posted on the dust-to-dust of CFL versus tungsten:
http://www.thewatt.com/node/175

By: Anonymous

Anonymous — Tue, 18 Mar 2008 14:59:54 +0000

I’m happy to see a good discussion going on here. The argument about seeing electricity on a continental, not state or provincial basis, is a good one and I didn’t factor this into my analysis (or the study on which it was based). Joseph Romm also pointed out this issue for me. Also, the point about energy input for manufacturing CFLs versus incandescents is also a good one. These are the kinds of issues that need to be raised, in advance of talk about completely banning the bulbs. There’s also the issue of quality: Many of the promises of CFL life are simply false, or not consistent with the many letters I’ve received from readers. The lack of dimming, and the fact that incandescents are valuable in situations where lights are rarely turned on, leads me to believe that we’re better off providing incentives to encourage the use of CFLs where they make the most sense.

As demand for incandescents go down the price will begin to rise. Meanwhile, CFLs are get better and the price will fall. The market will take care of the phaseout, and hopefully we’ll soon see affordable LEDs come onstream.

Again, I’m not arguing that most lighting needs need to transition to CFLs. I’m arguing that an all-out ban doesn’t take into account the various situations in which an incandescent may make more sense — both economically and from a greenhouse gas perspective.