Here's the house where I live in the Canadian province of Prince Edward Island with my partner and our son:

It's a 182 year old, 2000 square foot wood-frame house in the middle of the capital city of Charlottetown.

Every month we get an electricity bill from Maritime Electric, the private company that generates and distributes electric power here.  And every month I just pay the bill without looking at the details of how much electricity we've used in our house and how much its costing us.

If one of the keys to climate change mitigation is using less carbon-emitting energy, it seems that understanding how much electricity I'm using right now is an important place to start.

On the outside of our house is an electric meter that looks like this:

The meter measures electricity usage in kWh – kilowatt hours – and every month on our electric bill there's a section that displays the previous month's reading of the meter, the current month's reading and the difference between the two, which is the total kWh we used over the month:

So in the month of September we used a total of 563 kWh of electricity.

But what's a kWh?

There are all sorts of complicated explanations, but the simplest one is this: it's the electricity it takes to power a toaster for an hour.

A kW, or kilowatt, is 1,000 watts. If you use an appliance, like an average toaster, that uses 1,000 watts of electricity, for an hour, you've used 1 kilowatt hour. So using 563 kWh of electricity in September was the equivalent of running a toaster for 563 hours (or, if you like, running 563 toasters for an hour).

There are three of us living in our house, so using 563 kWh in September means that, on average, we each used used 6 kWh of electricity a day (563 kWh / 30 days / 3 people).

Here in Prince Edward Island we currently pay 14.31 cents (about 0.08 Euro) per kWh, so our electric bill for September was 563 kWh x 14.31 cents, or $80.57.  Added to that are a monthly flat service charge, a voluntary "green power" program used to fund public wind energy projects, and tax, for a total monthly bill of $116.96 (about 73 EUR):

Our 563 kWh of electricity in September was a little less than our average monthly usage of 600 kWh over the past year; our total usage for October 2008 to September 2009 was 7,203 kWh, something I know because every month's bill has a handy Your Consumption History section in the margin:

Our yearly usage of 7,203 kWh places us, according to Greenpeace, at 65% of the U.S. average household consumption, but about 150% of the average household European usage.

Maritime Electric sold 1,035 gigawatt hours of electricity in the Prince Edward Island in 2007 (according to the annual report of its parent) – a gigawatt, or GW, is one billion watts.  That's an almost impossibly large number to conceive of: somehow "running a billion toasters for an hour" doesn't create a useful picture in the mind.

Part of the problem with understanding energy issues is that it's these really big gigawatt and megawatt hours that are thrown around, numbers that are abstracted enough from personal reality as to be useless.

Thinking about single-household numbers, though, like 563 kWh a month, or 7203 kWh a year, once you understand what the numbers mean, keeps things reasonably simple. And once that 7203 kWh becomes more than just an abstract number, it's possible to get a real sense of how to change it.

For example, our clothes washing machine broke down this week in a way that makes it impossible to repair, so we're in the market for a new one.  Washing machines these days all come with ratings of the number of estimated kWh they'll consume in a year.  Using websites like this one we can explore the various models available, and find that models range from a low of 100 kWh/year to a high of 500 kWh/year.

If we purchase the 100 kWh/year washer, then we've just knocked a 400 kWh/year, or about 5%, from our annual electricity usage, a number that wouldn't really be all that helpful until I learned what our actual usage is.

While that 5% is, admitedly, the "low hanging fruit" of our electricity, it's not impossible to conceive of knocking an additional 25% from our yearly total simply by being smarter about purchasing and usage. 

And while that would only save us $280 a year in electricity costs, if every household in Prince Edward Island was able to do the same, we'd collectively save 24,800,000 kWh. 

Which seems like an awful lot.