Bob is dead right. And to further reduce the power consumtion, while the maint' men are taking the tubes out, have them simply disconnect the unused ballasts. This will save an additional 35-50 watts per fixture. Think about it; if a building has 2,000 four-tube lights (and many, many, have more than that), the building electric load will drop 35-50,000 watts instantly, if half of them are disconnected (that's enough to power about four all-electric homes!) At 10 cents/kwh (10 hr/day/5 day/week 52 weeks/yr), that's $3.5-5/hr, $35-50/day, $175-250/wk, $9,100-13,000/yr! That's a heck of a return, just for disconnecting ballasts. There are digital lighting controllers, designed for magnetic ballast circuits, which reduce power usage by 20% or more. Flourescent lights, like mercury vapour, metal halide etc', need high voltage to start, but don't need it after that. These controllers actually sense and monitor an inductive load, and only give it what it needs to operate. We have models which work on all inductive loads, including motors as small as refrigerators, and up to 500hp and bigger. My website will be up in 2-3 weeks, they will be available there. Sorry if I rambled on, but energy conservation is a passion with me. Have a great day, all. Brian. The site will be www.energysaviours.com it's being built at the moment.