Voltage Reduction

For the House


The concept of voltage reduction is pretty straightforward. When power is delivered to the household via the network it can fluctuate in voltage (on average) between 225 and 240 volts. The closer the household is to the transformer the higher the fluctuations.

The majority of household appliances only require 215 volts to function normally, so whenever you have an appliance on (be it a TV, fridge, washer, dryer etc) there is a potential saving of over 10% of the running costs.

The Voltage reduction system takes the fluctuation inflow of power from the grid and makes it a consistent 215 volts throughout the household.


To understand the potential savings the first thing to do is understand how your individual household is affected by fluctuations in voltage. This can be done by gaining an assessment from a professional. If your household experiences higher voltage fluctuations then there is the potential to save over 10% of your power usage. The less susceptible to voltage fluctuations your household is, the less potential saving.


There are a few different brands in the market each with their key attributes but a standard household unit will start from under $1,000 excluding service and installation. The key will be to understand the payback period and the ongoing savings that can be achieved. We recommended seeking the advice of a professional to get a complete understanding of how a voltage reduction unit can save you energy, money, and reduce carbon emissions.


The availability of energy efficiency programs and/or incentives for voltage reduction may vary from state to state. For the latest information we recommend requesting a quote from a professional energy efficiency company.


Voltage optimisation is an electrical energy saving technique which is mainly installed in series with the mains electricity supply to provide a reduced supply voltage for the site's equipment. Typically, voltage optimisation can improve power quality by balancing phase voltages and filtering harmonics and transients from the supply, although not always. Voltage optimisers are essentially transformers used to deliver power at a reduced voltage from the raw mains supply.

The term voltage optimisation is frequently misused, as the term implies some form of selective voltage reduction, which will improve the energy consumption within a building, whereas generally these units consists of a transformer within a box, offering no selectively and dropping voltage on all supplies, whether this would offer a commercial benefit or not. Some VO units have been installed on high frequency lighting circuits, offering little or no commercial benefit, therefore one must be careful when the term is used.

Most VO units are installed in commercial premises, in between the raw mains transformer and main low voltage distribution board. However, this provides for no selectivity and in electrical engineering terms is considered a poor solution. A full study should be undertaken by the facilities manager and VO company, to select which supplies could benefit the owner by reducing the voltage and which supplies would give no commercial benefit. This way the owner only purchases a VO of the correct size and not one that's for all supplies. Installing a VO unit to 'optimise' all supplies would give a longer return on investment, a higher capital outlay and makes no commercial sense.

Common power quality problems


Overvoltage refers to voltage higher than the voltage at which equipment is designed to operate most effectively. It causes a reduction in equipment lifetime and increases in energy consumed with no improvement in performance. The 16th edition of the Wiring Regulations BS7671 makes the following statements in relation to overvoltage: “A 230V rated lamp used at 240 will achieve only 55% of its rated life” (referring to incandescent lamps) and “A 230V linear appliance used on a 240V supply will take 4.3% more current and will consume almost 9% more energy.”

Various technologies can be used to avoid overvoltage, but it must be done so efficiently so that energy savings resulting from using the correct voltage are not offset by energy wasted within the device used to do so. Reliability is also important, and there are potential problems inherent in running full incoming power through electro-mechanical devices such as servo-controlled variable autotransformers.

Undervoltage refers to voltage lower than the voltage at which equipment is designed to operate most effectively. If the design of the VO does not take into consideration voltage drop over distance to remote power users, then this may lead to premature equipment failure, failure to start up, increased temperature in the case of motor windings and loss of service.


Harmonics are current and voltage waveforms at multiples of the fundamental frequency of the 50 Hz (or 60 Hz) main supply. Harmonics are caused by non-linear loads, which include power supplies for computer equipment, variable speed drives, and discharge lighting. “Triplen” harmonics (odd multiples of the third harmonic) result when phase voltages are not balanced in a three phase power systems and add in the neutral, causing wasteful currents to flow.

The possible effects if the level of harmonics, known as total harmonic distortion becomes too high include damage to sensitive electronic equipment and reduction in the efficiency of the HV transformer. The efficiency of electrical loads can be improved by attenuating harmonics at the supply, or by preventing their generation. Some voltage optimisation devices also mitigate harmonics, reducing losses associated with harmonic content on the electrical system.


Transients are large, very brief and potentially destructive increases in voltage. Their causes include lightning strikes, switching of large electrical loads such as motors, transformers and electrical drives, and by switching between power generation sources to balance supply and demand. Although they typically only last thousandths or millionths of a second, transients can damage electronic systems causing data loss, degrading equipment components and shortening equipment life. Some voltage optimisation devices include transient protection.

Phase voltage imbalance

Industrial and commercial sites are supplied with 3-phase electricity. Imbalance between the phases causes problems such as heating in motors and existing wiring, leading to wasteful energy consumption. Some voltage optimisation devices are able to improve balance on the building's electrical supply, reducing losses and improving the longevity of three phase induction motors.

Power dips

Power dips are reductions in voltage, mostly of short duration (<300 ms) but sometimes longer. They may cause a number of problems with equipment, for example contactors and relays may drop out causing machinery to stop. There are a number of low voltage ride through techniques including Uninterruptible Power Supplies, the use of capacitors on low voltage DC control circuits, the use of capacitors on the DC bus of Variable Speed Drives. Care must be taken that Voltage Optimisation measures do not reduce the voltage to an extent that equipment is more vulnerable to power dips.