We often know what the right thing to do is - but that doesn't mean we do it. Our own comfort can dominate our decision-making.
Air conditioning, for example, eats up energy. As summers get hotter, what once seemed unnecessary now seems like an essential.
So it is with the Nishi building, that funky landmark in New Acton.
It is world famous for its environmental credentials. The Danish Design Centre in Copenhagen describes it as "progressive, quirky and vibrant" and singles out the apartments for particular praise because they "rely exclusively on natural ventilation".
Not any more.
It turns out that the building owners' corporation has voted to allow unit owners to install concealed air conditioning units on their balconies, reversing previous regulations which effectively banned them.
We can't blame the inhabitants of apartments for wanting to stay cool in the rising heat of summer. Or the owners of the building for wanting to make the apartments more attractive to renters and buyers.
But the decision does illustrate a dilemma. The hotter our planet gets, the more we want to keep cool - but keeping cool is energy-intensive.
It is true that the ACT power supply is from non-carbon sources but the country as a whole still burns coal. And if clean energy powers air-conditioning units, that clean energy is not available for other uses.
There is a national dilemma: hotter summers increase demand for electricity, some of which comes from coal-burning power stations.
It is a great irony that our response to global warming is to buy more power-guzzling air-conditioning. A small unit to cool a single room eats up more electricity than running four fridges.
It's a very human dilemma: we know about high-energy usage but who wouldn't turn on the air-conditioning on a plus-40 Canberra day?
The dilemma shows the need for a coherent energy policy which puts a high price on high energy usage.
It might persuade people in the fancier apartments to open a window and just take in the natural breeze instead of ramping up the AC.