Canada. A place that conjures up images of snowy, forested mountainscapes. Or perhaps expansive golden wheat fields. Or maybe gently rolling hills speckled with glacial lakes. As diverse as Canada's landscapes are, so are their cities. And so are their infrastructure. And, so it follows, so are their carbon emissions. If you live in Vancouver, Montreal, or Winnipeg, with their access to abundant hydroelectricity, you might have a lower climate impact when you switch on the light than if you live in Edmonton, Toronto, or Halifax. Take a look at the figure below - you can see that the emissions per unit of electricity you consume varies quite a bit (presented here in g/kWh, using 2010 data). Once you consider building age, appliance efficiency, and types of residence that you live in (i.e., apartment vs single family detached home), you can expect a quite varied emissions profile when looking at different cities.

So out of curiosity, I set out to quantify the greenhouse gas emissions that residents in various Canadian cities would be responsible for just be the act of operating their house. Of course, this wouldn't include emissions from transporting themselves away from their house, or consuming non-energy resouces within their house, but just the day-to-day operations - cooking, turning on the lights, washing the dishes, showering, heating, cooling, and so on. Because Canadian cities developed at different times and have access to different resources, there is bound to be a difference in the characteristics of their residential building stock and the types of energy they consume. With the aid of my co-author, I explored just how different my selected Canadian cities are in the residential carbon emissions. You can see the result (in tonnes of CO2e annually) from the average person living in the average home in 2010 presented in the figure below.

Explaining These Results

So why does a resident of Halifax have a such a drastically higher household carbon footprint than a resident of Montreal? Well, the underlying abundance of electricity has a huge role to play. First, whatever applications that use electricity in the household (lighting, appliances, heating, etc) are inherently low carbon, which is a nice starting place. Next, because electricity is just so abundant in the province, you can use it in applications that you wouldn't have otherwise, specifically space and water heating. So when a Montrealer cranks up their thermostat, the energy is mostly sourced from clean, hydroelectric (and increasingly wind) power. But when a Haligonian seeks reprieve from the blustery maritime winters, the energy comes from fuel oil or the coal-heavy electricity grid.

One thing that did surprise us was just how little an impact a city's development history had. Montreal has a larger collection of older buildings when compared to a city that has seen a lot of recent development, such as Edmonton. However these differences are overwhelmed by the effects of the choice of fuels within households and within the regional grid. As a result, you can see that a city's emissions are more or less in line with the carbon intensity of their electricity grid.

How do we improve the carbon intensity of the grid?

Now that we know that a clean grid can mean guilt-free living (from a carbon perspective) in Montreal & Winnipeg, the next question becomes how do we all get to this point. Clearly not every province is endowed with the hydroelectric resource available in Manitoba, British Columbia or Quebec. So what can those provinces do? Carbon neutrality in these cities will require a dramatic reduction in energy demand that can be sufficiently met by local/imported low-carbon electricity. So it's a matter of creating an environment where demand reduction occurs naturally, through the market. A price on carbon is the first step. Other important approaches were discussed by Jesse Row and I in a Pembina Institute publication, with some key approaches being:

• Mandatory building energy labeling, so that people know the energy performance of the buildings they buy/rent
• Informative billing / home energy reports so that people understand how their energy consumption compares with their neighbours
• Aggressive building code improvements to ensure future homes are built to a very high energy performance standard (to give you an idea, Sweden has discussed making residential buildings require no more than 75 kWh per square metre by 2020 - the average Canadian house used over 200 kWh per square metre in 2011

If you'd like to read more about the research that we did, you can download it in pre-print draft here or if you have access to the Canadian Journal of Civil Engineering, you can obtain the published draft here.