B.C. is phasing out incandescent bulbs for home use, and that's raised some interesting questions about the environmental and health impacts of the bulbs that are replacing them. My colleague Lindsay Coulter outlined some of the ways to properly dispose of compact fluorescent bulbs. But some people are rightly questioning what the total greenhouse gas impact of the CFL phase-in will be if we account for the energy incandescents provide to heat our homes.
The Vancouver Sun reported BC Hydro's estimate that the new CFL bulbs will increase B.C.'s GHG emissions by 45 kilotonnes. I don't know how BC Hydro came up with this estimate, but I assume that the utility looked at the additional energy required to make up for the lost heat from incandescents and calculated the emissions split between homes heated by electricity and homes heated by natural gas. If all of the heat energy from incandescents went to heat homes, the electricity and GHG savings would be zero because just as much electricity would be required to replace that lost heat. Because incandescents and electrical element heaters have the same efficiency, there would be no net effect on energy and GHG savings. And so, the increase in provincial emissions would come from homes heated with natural gas as more natural gas would be needed in home furnaces to make up for the lost heat.
But there are a number of problems with this type of calculation. First, CFLs actually lead to a net energy savings even when accounting for the lost heat. In 2008, Natural Resources Canada and the CMHC studied the net energy savings when accounting for heat loss. They found that in all cases, CFL bulbs lead to total energy savings. Why? For a couple of reasons. First, not all of the heat from incandescent bulbs was used; bulbs close to windows or recessed in ceiling light holders do not provide useful heat. Second, the heat from incandescents is not helpful during warmer seasons and can lead to more energy consumed by air conditioners to cool homes. Because seasons are so variable across the country, the study looked at homes in a number of different locales. In Vancouver, for example, CFLs reduced energy by 318 kWh per year while the increase in heating energy required was 201 kWh for electric-heated homes and approximately 226 kWh for natural-gas-heated homes. Therefore, electricity emissions would drop while natural gas emissions would increase. Because the emissions footprint of B.C.'s electricity system is quite low because of its reliance on hydropower, the additional natural gas used for heat would result in an increase in emissions.
But, this is only looking at B.C. If we look at the total electricity system, the story gets more interesting. B.C. imports significant amounts of electricity annually from Alberta and the U.S. This imported electricity is more GHG-intensive as it is either coal fired (from Alberta) or natural gas fired (from the U.S.). To put it in perspective, B.C.'s average emissions from an additional kWh of electricity generated is about 28 grams of CO2. For coal-fired electricity it is 800 to 900 grams and for natural gas it is 200 grams. That means that if the electricity savings from CFL bulbs go, in part, to reducing imports, then the effect on total emissions will be positive.
And because natural-gas furnaces are anywhere from 80 to 97 per cent efficient in Canada, between 80 and 97 per cent of the energy in the combusted gas goes to useful heating. This is important to understand if we start replacing incandescent heat with natural gas furnace heat. Why? Because imported electricity used to power the incandescent light bulbs is much more inefficiently produced than a natural gas furnace. The best efficiency natural gas generating stations achieve 60 per cent efficiency, and coal plants are anywhere from 25 to 40 per cent efficient at producing electricity. So when you use incandescents for heat, you've already lost a significant amount of energy by the time the electricity reaches your light bulb. Significantly more energy is used than with a natural gas furnace.
As a result, if we look at system emissions, (which is what is really important for a global pollutant like CO2), total emissions from using CFL lights will be lower.