We publish that converting from V-belts to synchronous belts will save an average of 5% of the drive's energy consumption. Sometimes this can be confused with measurements taken to confirm energy savings by end users.
Note that the 5% is an average estimate.
Both highlighted words at the end of that sentence need further explanation.
The savings is an average value because the savings comes over time. Newly installed and properly tensioned V-belts running in good sheaves are going to be very efficient. Comparing a newly installed synchronous belt drive with an instantaneous measurement to a newly installed and properly tensioned V-belt drive, or a newly re-tensioned V-belt drive will most likely only show a couple of % difference in energy savings for the synchronous belt drive.
Average is just that - an average over time that demonstrates not only the reduced bending stresses and cooler operation of synchronous belts, but also the natural trend of increased slip and creep of V-belt drives...over time. An average value isn't a guarantee of a minimum 5% performance increase, but is an average over time.
If an attempt is made to measure efficiency gains, that measurement is only a small slice of the average total result. Its an instant out of the entire operating period, and not representative of the overall efficiency gain.
The savings are also quoted as an estimate. This is done because every drive and circumstance is different. The savings gain from a conversion of poorly maintained systems will most likely exceed 5%. The savings from converting a well maintained system may not achieve 5% savings. Systems that are redesigned to use the consistent speed of a synchronous belt drive can more accurately run at speeds that are actually needed to do the work required may have dramatically higher savings. Extensive field tests, confirmed by laboratory testing, has confirmed that the estimate, of average savings, is reasonable to use at 5%.
So - keep the above in mind when discussing or handling the energy efficiency issue. Don't use an estimated average value to guarantee a minimum instantaneous expectation.