Voltage Optimisation is one of the many methods in the market that assists in energy saving. It is the intelligent new approach to help reduce electricity bills.

In the UK the electrical supply infrastructure has been historically designed to operate between 235-245v compared with 220-230v across Europe. This reduces transmission losses and helps maintain the supply voltage for all consumers over large distances and during periods of heavy demand. Therefore, the electricity supply companies have no alternative but to generate at the top end of the legal voltage range agreed for all European countries, but most appliances have a nominal voltage of 217-253V so motor appliances will be running faster and harder than is necessary. So the nominal value of power supplied by network providers to its customers is higher than the nominal value required for running equipment. The idea is that if the supply voltage can be reduced, the electricity bill will be reduced.

Excessive supply of voltage is costly, wasteful and damages electrical appliances by increasing the heat generated by the motors. These problems can be resolved by using A Voltage Optimiser. If the reduction in supply voltage is carefully matched to the needs of the connected electrical equipment it is possible to make a substantial energy saving and extend the life expectancy of the connected equipment.

The design is based on the provision of appropriately optimised voltage levels for real electrical equipment, allowing tasks to be carried out more efficiently. Voltage optimisers (VO) typically offer a wide range of adjustments to achieve higher levels of energy savings and lower losses, providing an advantage over the site isolation transformer.

Voltage optimisers systematically reduce the voltage of the mains power supply entering a domestic, commercial, or industrial building to reduce the level of energy uses and reactive power. Some voltage optimisers have a fixed voltage adjustment, whilst others can automatically and electronically regulate their supply voltages. Commercial building and industrial voltage optimisers tend to be based around auto-tap-changing transformers, with advanced electronic control circuitry, whilst smaller domestic voltage optimisers usually use a toroidal type transformer.

Installing a voltage optimiser in a property that has a solar PV installation can provide additional benefits such as an overall reduction in energy consumption, together with a reduction in wear and tear on electrical systems and appliances, especially if the AC voltage from the solar inverter is higher than the local mains power supply.

They are relatively straightforward to install within about half an hour and do not involve rewiring or replacing your power supplier. The voltage optimiser should ideally be placed between the consumer unit and its AC power sources: the mains power supply or a solar PV inverter.

Potential Savings

The following voltage optimisation examples of savings are based on a 7.5% voltage drop (242Vac to 224Vac)



Appliances with Motors

A-rated Fridge/Freezer 16%, 3-speed heat pump 15-18%


Resistive heating 14%*


Compact Fluorescent Lighting 11%, Sodium/Discharge 15% Halogen 12%, High Freq Fluorescent 0%


Air Compressors 12%, Circulation pumps 12%, Fans 12%, Vacuum cleaner low power 24%, Vacuum cleaner full power 16%


CRT 5%, Plasma/LCD 0%, PC 4%, Laptops average 6%, Radio 9%, Printer 7%, Scanner 12%

Consumer Electronics

DAB Radio 5%, DECT phone base station 30%, ADSL modem and wireless router 5%, HiFi 13%

*thermostatic control will result in a much smaller saving.

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