It is also important to factor in the shade that will be produced by the fixture. In some fixtures, the ballast is mounted above the reflector. However, top-mounted fixtures are taller, which means they can't be used unless there is sufficient head room. The other benefits to remote-ballasted units are the significant reduction in electrical installation costs and the much lower fixture weight. When it comes time to actually price lighting systems, you'll find that the least expensive options are for 400-watt sodium or halide lamps and mounted ballasts.
Costs increase with remote-mounted ballasts, special lamp types and voltages, and other options.
On the other hand, these systems are built to last. For instance, the ballast electrical components are usually warranted for up to five years. Peter Wardenburg is vice president of Hydrofarm Greenhouse Lighting, Petaluma, California. America P.O. Box 3075 San Ramon, California 94583 Reprinted by permission.