Maybe it's generational (I'm GenX), so I'm not sure if all Canadians muddle through both systems as much as I do but I seem to live in a constant superposition state between Metric and Imperial, with little sense about which I'll use for any particular purpose.
I use Celsius for cooking and low temperatures, but Fahrenheit for body temperature and most room temperatures; kilometres for long distances but inches and feet for height and most short distances; pounds for body weight, but never ounces (for that I use grams), for cooking and large weights I seem to mostly use metric units. Volumes are almost exclusively metric, I suspect because we also went through a transition when gallons shrunk from Imperial (4.54609 litres) to US gallons (3.785 litres).
I envy European consistency when it comes to metric.
Now, presume there is no gauge at hand to measure a pound less a thermometer to measure fahrenheits. Often outside of commonwealth territories and US we use SI :)
Firstly, I'm Australian. We use SI measurements - your comment is not just smug, but wrong.
Secondly, are you honestly postulating that people understand the underlying reality of what a kilowatt hour actually means? That they have a "gauge" that can measure kilowatts? Of course they don't, and for that matter most people that use BTUs don't really understand what they represent either. They just know that it's a measurement of energy-use. All they really want is something that allows them to compare two options, and frankly, the units matter not at all.