We thought we’d finally discovered The Big Heavy: we received an ad for a 2 ton air conditioning unit. It’s common knowledge that most window units are hardly featherweight, but still! We wondered how large, exactly, was this behemoth of a cooling system? Visions of stories-tall machinery danced in our heads.

And then we researched it a bit, which put that 2-ton unit into perspective (you might even say it cooled our jets). Rather than the marvel of machinery we’d envisioned, the image of that unit was rather pedestrian. Boring, even. It was precisely the kind of cooling system you’d see outside any home or small office. In fact, it looked something like this:


So where does the “ton” measurement come from? Surely it can’t indicate the weight of this thing, right?

Ton is a measurement of the cooling capability of an air conditioning or refrigeration system; in fact, it works out to be the equivalent of 12,000 BTU/hour (we talked about what BTU means a few months ago). But why use the word ton? Well, it’s a bit of a holdover from the days when technology was making the transition from using actual stored ice (!) to mechanical systems. It’s the same amount of cooling power that would be generated by melting a ton of ice in a 24-hour period.

Which, actually, is pretty cool. In every sense of the word.