Voltage optimisation is a term given to the systematic controlled reduction in the voltages received by an energy consumer to reduce energy use, power demand and reactive power demand. While some voltage 'optimisation' devices have a fixed voltage adjustment, others electronically regulate the voltage automatically.
Voltage optimisation systems are typically installed in series with the mains electrical supply to a building, allowing all its electrical equipment to benefit from an optimised supply.
Background
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 selectivity 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 little commercial sense.
United Kingdom
The declared low voltage electricity supply in the United Kingdom as per the Electrical Safety, Quality and Continuity Regulations 2002, is now 230 V with a tolerance of +10% to -6%. This means that supply voltage can theoretically be anywhere between 216 V and 253 V depending on local conditions. However, the average voltage supplied from the national grid (in mainland UK) is 242 V, compared to the typical European voltage of 218-222 V. (The average supply voltage in Northern Ireland is around 239 V, and 235 V in the Republic of Ireland.)
Older electrical equipment manufactured for the UK was rated at 240 V, and older equipment manufactured for Continental Europe was rated at 220 V (see Worldwide Mains Voltages). New equipment should be designed for 230 V. A mixture of equipment is likely to be found in older premises. All equipment placed on the market within the E.U. since voltage harmonisation in 1995 should operate satisfactorily at voltages within the range 230 V +/-10%. Equipment rated at 220 V should operate satisfactorily down to 200 V. By efficiently bringing supply voltages to the lower end of the statutory voltage range, voltage optimisation technology could yield average energy savings of around 13% .
The higher the voltage the higher the power consumption in the case of a pure resistance load. A reduction in voltage does not affect the energy used by the domestic appliances which use resistive loads except in devices such as kettles and toasters which will take longer to do their job due to atmospheric losses. The main commercial benefit when installing VO units, is on inductive loads, like motors which run pumps, fans and the like. In the home, the potential energy saving can be up to 12% on electricity bills. A VO device will lower the voltage to the most efficient level to maximise the savings on electricity consumption, so you may notice certain things taking a little longer, such as a kettle may take a little longer to boil.