It's crazy when you think about it. From showering in the morning to draining the pasta for dinner, we each put gallons of hot water down the drain every day.
Mix it all up, and it's enough to keep our sewers flowing at a balmy average of 15C. That's a lot of energy babies being thrown out with our bathwater.
I've always thought there should be a way to re-use that heat, but I suspect the demand for lukewarm sewage-filled radiators is fairly modest. Luckily, there's another way.
In a year of record-breaking extreme weather, it's never been clearer that we need to step things up in a big way.
But when it's time to do more, it's also worth reminding ourselves what we're capable of.
So to celebrate another remarkable year, we've put together a big roundup of the best things we did together in the last 12 months. As always, it makes for pretty inspiring reading!
Ever wondered if we've got what it takes to get climate change sorted? Here's your answer.
And between being blown away by all your beautiful photos, we've been working on a little something of our own...