I was talking to a building manager about energy conservation the other day (as you do) and he pointed out a quirk in the way we decide whether or not to install energy saving devices.

He was looking at the choice between installing motion sensors or LED lighting for lights in common areas.  He calculated that if they installed LED lighting, the savings would repay the costs in, say, two years (these figures are NOT accurate – I'm just using them to make a point).

He discovered that putting motions sensors in common areas would be repaid in just a few months.  “OK,” said an enthusiastic EC member, “Do both and we'll save heaps.”

Not so. The smart BM went back to his calculator and discovered that by doing both, it would take more than 20 years to recoup the costs. 

How can that be? Well, if you put motion sensors in common areas like lift lobbies, for instance, the lights are on for such short periods that the benefits of LED lighting are spread very thinly.

He installed motion sensors that, he says, are so efficient residents don't even realise the lights weren't on until the opened their doors.

That's enough from me – if you want sensible advice go to GreenStrata.