Efficiency is simply the power coming out of a unit divided by the power going into a unit, usually expressed as a percentage. 
All
voltage regulators and power conditioners "consume" energy in the
process of performing their task. Typically this consumption is in the
form of losses that occur within the components (e.g. transformers)
where the lost electrical energy is converted to mechanical energy in
the form of heat or motion (vibrations). Efficiencies can run the
spectrum from less than 50% to 99%. Most units will have efficiencies
that are relatively constant across the load range, however
ferroresonant transformer-based units tend to have efficiencies that
fall off very quickly for points below full load. Efficiency may
be one of the most overlooked parameters when selecting a voltage
regulator or power conditioner. A quick gauge of the cost of
differences in efficiency can be had by multiplying the KVA size of the
units by the difference in efficiency by 7. The result will be an
approximation of the annual energy cost difference (at $0.08/KW-HR) in
dollars. For example, for 25 KVA units with a 3% difference in
efficiencies, the unit with the lower efficiency would cost about $525
more per year in extra energy consumption. |