Enter the lair: Upgrading 30+yo t12 fluorescent fixture to modern technology
Channel: Daniel De Jager
Date: 2013-08-24

In this video I replace the T12 ballasts (plural) in a fixture in our garage to modern T8 bulbs and ballasts.
The fixtures originally were built in the 70s and as such came with 2 magnetic ballasts per fixture. 
I replace them with a single 4 lamp electronic ballast.
just going from the nameplates: 2x .6A ballasts = 144w
Now: 1x .8A ballast = 96W
Now we get 10% more light for 1/3rd less power. AND NO HUM!
The ballasts were $15 on amazon and the bulb were not special prices (The tubes needed replacing anyways, so I feel that I can ignore the price of the tubes)

At $0.10 The new lamps and ballasts save $0.0048/hr that they're used.
Payback time: 3000hrs.
At the rate that they're used, they will pay for themselves in 1 yr!

PS: I can't be bothered to edit this, so what you see is what you get.