A while back I did an energy audit in my house. Fortunately for me I do live in an area served by cheap hydroelectric and coal energy. Well, fortunately for my pocketbook anyway. Regardless, I'm ever attempting to reduce my energy needs for both personal and altruistic reasons, hence the audit.
I surveyed all the lights in my home, noted their location, type, wattage, etc. When we moved in, most of the lights were old school incandescents. Altogether they added to 2918 watts of lighting. By swapping in a few compact fluorescents I've reduced that total to 1778. That's a savings of 40%. Impressive, but not so fast. Are all those lights used the same amount? Definitely not. The garage lights are on for probably only 10 minutes per day, on average. So clearly we need to factor actual usage into the equation.
So I also estimated the average usage of each bulb. Yes it was as fun as you think. What I found is that our 2918 watts account for about 4950 watt hours of actual usage per day. After my upgrades that dropped to 3274 watt hours, for a savings of 34%. If you notice that's less than the 40% we calculated earlier you get a brownie point. Indeed some of the lights we use the most are ones that I cannot reduce any further.
Even more interesting is something I've recently come to understand as I make a concerted, although to many unquestionably bizarre, attempt at understanding statistics. Quite often a very small number of things will often account for most of your results. A good example is the US federal budget. While McCain notably complained about earmarks in bills (which may be undesirable for many reasons) they account for a very small fraction of the money spent. If you want to make any reasonable dent in the outlays your best bet is defense, social security and medicare/medicaid which account by themselves for 65% of our expenditures.
Getting back to the original point (and hopefully avoiding a political tangent), I found that just a few of the lights in the house account for the majority of the electrical usage. In fact, the two sets of fluorescent lights in the family room account for nearly 60% of the total electricity. Even if I were to upgrade the rest my bulbs to compact fluorescents, it would only decrease my current usage by another 15%. I'm pretty much bound by those two sets of lights.
The exercise was a useful one. I'm on a slow quest to analyze all the electrical usage in the house. The light bulbs were the easiest to tackle. Some time I'll move on to the appliances and computers. The latter I'm rather apprehensive about. I might rather be ignorant.