In the maintenance of lighting systems, it can often be said that the lowest price does not result in the lowest cost. In the application and replacement of fixtures, lamps, tubes, and controls, the matter of selection and replacement is sometimes more complex than expected.
Since the late 1990's, it has been impossible to buy the old four - foot, 40 - Watt "cool white" fluorescent tube that was commonly used in lighting fixtures. It was outlawed by the Energy Efficiency Act (EPACT in the U.S., EEACT in Canada) effective in the mid - 1990s. To fill the void, manufacturers of fluorescent lighting systems introduced and aggressively marketed a number of new, energy - saving products including a 34 - Watt replacement for that lamp.
The problem is that, although the 34 - Watt energy - saving lamp will fit and work in older fixtures, it may not necessarily be the best and most cost - effective choice for replacement.
In the U.S., the National Electrical Manufacturers Association (NEMA) was quick to announce that use of the new lamp with ballasts produced before the new lamps were introduced might result in outages and ballast failures due to incompatibility. In some cases, use of the lower wattage tube actually resulted in higher power consumption and overheating of fixtures with consequent ballast failure, in other cases, ballasts failed internally. In some systems, as many as one - third of older ballasts have been known to fail as a result of this misapplication.
In any case, it is safe to say that any fluorescent tube should not be used with a ballast that is not specifically identified as being suitable for that type of lamp. At the very least, reduced lamp life may result from unsuitable operating conditions resulting from the mismatch.
For those wishing to explore the possibility of reduced energy consumption in a fluorescent lighting system, it would be more sensible to consider replacement of existing ballasts with energy - saving units designed to work with reduced - wattage tubes, or conversion to other, more efficient lighting technologies rather than a piecemeal guesswork" approach.
For those who just wish to replace the lamps, it is still possible to get lamps that are compatible with the old ballasts, but they are a bit more expensive than the mass - produced 34 - Watt lamps.
However, when coming to a decision about which lamps to select, one should keep in mind that the replacement of a two - tube fluorescent ballast (the most common) can cost much more than the few pennies saved by using the wrong lamps. When the cost of materials, labour, permits and inspection (where required) and other factors are considered, a single ballast failure would probably wipe out the cost difference for a whole case of tubes.
In the event that no ballast were to fail, there are still the unpredictable possibilities of increased energy consumption (including increases in air - conditioning costs) and reduced lamp life.
Perhaps it would make sense to explore these matters before relamping with the cheapest tube.