Whilst the oven is on cooking what I fancy for my dinner I’ve always filled any empty shelves with food that could do with being baked and then frozen it for another day with the belief that I am saving energy by using up what would otherwise be wasted space in a hot oven, however, my question is this: am I in fact wasting energy by placing items upon an empty shelf that will now absorb energy to cook, energy that the oven must work to replace? Would it have been more efficient to leave the shelf empty so the oven needs only maintain the temperature?

I'm sitting here in the dim light of a CFL bulb, using my little laptop, sweating in the July heat because air conditioning is a giant energy-suck and wondering if any personal effort to reduce carbon emissions is worthwhile, when the Large Hadron Collider uses a gazillion bazillion teramegaelephantine watts of power.

I also get kind of bummed out when I watch NASA launch a space shuttle. Really, what is the point of me driving a tiny ultralow emission car?

My house is full of adaptors - a quick count came to over 50 (not all plugged in!). Many of them are attached to rechargeable devices.  I am aware that most of these act as "vampires" - drawing down power even when the attached device is charged. So I have a number of timer switches both mechanical (easier to use) and electronic (sophisticated but with hard to see LCDs and impossible without the manuals). I now find myself wondering whether the power used by these - a motor for the mechanical and presumably some kind of step down for the electronic ones might actually exceed the saving from say, turning off the charger on a DECT wireless phone?

The switches only tell me that they run at 240V and the wattage of the devices they can support - nothing about their power consumption.

In case anyone thinks the nature of the food is material to the answer, I have in mind, principally, meat.