We are currently involved with replacing about 5000 ballasts in a warehouse.

The originals fixtures where 2 lamp 8' high output T-12s, we convert them to 4 lamp 4' T-8s and the light output is much higher.

As far as the ballasts you need T-8 ballasts for T-8 lamps.

Also available are 4' T-5 high output lamps which with 4 of them can replace a 400 watt HID fixture.

Bob Badger
Construction & Maintenance Electrician
Massachusetts