re:Instant Start

In message "Aquatic Plants Digest V2 #354", you write:

>From: Erik Olson <eriko at wrq_com>
>Date: Sat, 30 Nov 1996 19:07:40 -0800 (PST)
>> From: "G.Tong" <gtong at sirius_com>
>> >HOWEVER, often in the APD, when we are refering to T-8's, we are talking
>> >about a TYPE of fluorescent light, not a size.  Specifically, T-8 is used
>> >to refer to high-efficiency Instant-Start bulbs.
>> Erik, you meant "Rapid Start," right? Instant Starts are short-lived.
>No, I meant Instant Start.  That's what it says on the ballast, at least.
>T-8 ballasts are hooked up totally different than Rapid Start NO's... BOTH
>pins are tied together at each end, so there is no separate starter wire.
>I don't know they start exactly, but I followed the directions.

There seems to be some mix-up in terminology here. 

To set the context - both bulbs *and* ballasts are classified as
either instant-start or rapid-start. Most combinations of ballasts
and bulbs will work:

                         Instant-start bulb    Rapid-start bulb
Instant-start ballast  |        OK            |      OK        |
Rapid-start ballast    |     WON'T WORK       |      OK        |

Rapid-start bulbs have two pins at each end, while instant-start bulbs
have only one pin at each end.  What Erik is using is apparently an
instant-start ballast with rapid-start bulbs.

On to the real reson for my posting.

Greg is right when he says that instant-start ballasts decrease bulb
life.  This is because they use a higher voltage to jump-start the
discharge than rapid-start ballasts, putting more stress on the
electrodes in the bulb.

However, this reduction in life is only about 25%, even if the bulbs
are switched on and off every three hours.  Given that plant people
replace their bulbs every year or so, this is probably not be a

Instant-start ballasts are usually a bit more efficient than rapid-start
ballasts, but the difference is only about 3 watts or so per bulb.  
At 10 cents per KWH, and 12 hours use per day, the savings would be about
$1.30 per bulb over a year's time.  Not terribly significant either, IMO.