On Sat, 31 May 2008 10:58:43 +0100, "Mary Fisher"
wrote:

It's a pretty exact science, or ought to be if you do it right.

I'm not sure about that because different weather patterns, geographical
locations and the needs/desires of households are different.

That's why you have to do it right. The data to support an accurate
model, down to a narrow geographical location, is obtainable.

Nor are the needs of different households all that different - there are
only so many ways to arrange a small number of people. The Jukes and the
Kallikaks might be different, but all of those Jukes living on the same
orientation in that same small town are going to have much the same
needs.