Go to CNF homepage
The Canadian Nuclear FAQ  

by Dr. Jeremy Whitlock


To The North Renfrew Times regarding free CFL bulbs distributed to homeowners through Project Porchlight:

(published in the 2007 Dec 27 edition)

Not as "green" as it seems?

To the Editor,

After receiving my free "Porchlight" CFL (compact fluorescent light) bulb last week I thought I'd figure out the real environmental impact of my replacing a 60-watt incandescent bulb with a 13-watt CFL bulb at this time of year, given that during the winter incandescent bulbs are 100 per cent efficient (two per cent of their energy is used for light, while the other 98 per cent heats my home). In other words, if I run a 60-watt bulb I'm adding 58.8 watts of heat to my home which I would otherwise have to supply by burning natural gas in my furnace.

Since in Ontario one quarter of our electricity comes from fossil (mostly coal) sources, while the rest is clean energy (hydro and nuclear), that 58.8 watts of heat is more cleanly generated with electricity than with natural gas.

Another way of looking at it is this: To generate the same amount of light with the CFL as the 1.2 watts of light generated by the 60-watt incandescent bulb, I have to use 13 watts of electricity (11 times as much electricity), and then I still have to generate the missing 58.8 watts of heat with my natural gas furnace.

To put this in terms of CO2 generated, I calculate that running an incandescent bulb for 24 hours in my home accounts for the emission of about 300 grams of CO2 from power plants (using a 25 per cent coal fraction).

To run the CFL bulb for the same 24 hours, plus make up the missing heat supply, accounts for the emission of about 800 grams of CO2, almost three times as much (ignoring the extra energy needed to make the bulb in the first place).

I realize the situation is different in the summer when the incandescent bulb's added heat load might have to be removed by air conditioning (although this isn't the case in my non-AC home), but I wonder if the winter reality I've described above has been taken into account by those behind the Porchlight campaign.

The simple fact is: If I burn the free CFL bulb in my home right now, I'm emitting almost three times as much greenhouse gas as an incandescent bulb.

The only way around this is to use the CFL bulb solely outdoors, in which case the heat of an incandescent bulb would have been wasted anyway, so it just comes down to the electricity burned per lumen.

Is this why the program focuses on using the bulb as a "porchlight"?


Jeremy Whitlock

[Back to The Canadian Nuclear FAQ]