Is it possible to save energy by using voltage reduction units which reduce the supply voltage?
The answer provided by Christian is the product manager for traditional lamps, LED lamps, LED light engines/modules and electronic control gear at OSRAM Australia.
Often people allege that when lowering the supply voltage by using an additional power transformer (voltage reduction unit) in a lighting installation, electrical energy will be saved without any noticeable decrease to the overall lighting levels. For the right answer, you must consider the effect that reducing the supply voltage has on different types of lighting technologies.
1) Thermal radiators (e.g. incandescent lamps, halogen lamps)
With the reduction of the supply voltage, the electrical power consumption will be reduced, but the luminous flux and the efficiency will decrease disproportionately.
Conclusion: Not ideal, therefore not recommended
2) Discharge lamps operating with conventional magnetic control gear/LLG
With the reduction of the supply voltage, the electrical power consumption will be reduced, but the line current increases. Hereby the electrical loss increases and the efficiency decreases. The luminous flux decreases and the colour appearance changes. But above all the life time of the lamps will be reduced.
Conclusion: Not recommended
3) Discharge lamps operating with Electronic Control Gear (ECG)
The reduction of the supply voltage will be compensated by the ECG with a higher current consumption. The luminous flux will be nearly constant, but the electrical loss increases, which is why the energy consumption increases and the efficiency decreases.
Conclusion: Not recommended
4) LED lamps with integrated driver
This is essentially the same as the above scenario with discharge lamps on ECG. The reduction of the supply voltage will be compensated by the driver with a higher current consumption. The luminous flux will be nearly constant, but energy consumption increases while the efficiency decreases.Conclusion: Not recommended