[LINK] Compact Fluros and energy inputs (was: Here's one ...)

[rchirgwin at ozemail.com.au]

Thinking more on this point:

>2. And what is the energy budget on manufacturing one of these bulbs.  What
>is the cost in terms of energy input in manufacture, transport, retail etc,
>compared with energy saved.
>
>I suspect that it is considerably on the plus side, but I'd like to be sure.
>does anyone have any figures?
>  
>
A thought experiment may do as well as figures, at least to provide a starting point.

I will make one assumption, and use one cheat to simplify the maths. The cheat is that I'll use Sydney domestic electricity prices - roughly 12.5c per kWh (but it doesn't matter, because one price unit = one price unit).

The assumption is that 50% of the cost of the final product is energy inputs. This is to me unrealistically high, so any error is penalising the more expensive product (that is, if less energy is in the cost, the compact fluro comes out better).

Incandescent - about $1 at Woolie's in a multi-pack (ie, two for $2). Energy input: 50c = 4kWh at 12.5c per kWh.
Compact Fluro - about $3 in a multi-pack (checked - $6 for two on the last docket). Energy input: $1.50 = 12kWh. 

Using a 100W to 12.5W comparison, 12kWh / 87.5W = about 137 hours to energy break-even (ie, 87.5W is the saved energy). At 3 hours per week, the break-even is less than a year (in energy input terms).

So in one year, you get financial break-even; and in two years, energy break-even in the worst case outlined above.

So Turnbull's specs should include MBTF!

RC