Voltage optimisation is an increasingly popular retrofit solution to the problem of reducing energy consumption and carbon emissions in existing buildings. Whilst it may sound as simple as fixing a gadget to your incoming electrical supply, the truth is that VO requires careful consideration to establish the suitability of your building.
What is Voltage Optimisation?
Voltage optimisation is the modification of the supply voltage to electrical equipment with the intent to reduce the energy consumption. Electrical equipment is designed to work within various voltage tolerances. The theory behind voltage optimisation is that a reduction of voltage from the UK standard will result in a reduction in power with no greatly adverse effects to the equipment.
There is a variety of voltage optimisation solutions available on the market ranging from 3 phase devices installed at the main incoming point of the electrical supply to control the voltage to the whole building, to local single phase devices controlling the voltage to a single piece of equipment. Single phase units for domestic use are also widely available.
The typical device is designed to reduce the supply voltage from the standard UK supply voltage of 230V average down to 220V average.
How does Voltage optimisation work?
The reduction of supply voltage will affect different types of electrical load in different ways. While some loads such as luminaires with magnetic ballasts can achieve energy savings from being fed by a lower voltage, others such as electrical equipment with switch mode power supplies will draw a constant power regardless of the supply voltage resulting in no change to the energy consumption and an increase in current drawn. The below table summarises the effects on certain loads.
| Electrical Load | Effect of Voltage Reduction |
| Lighting – Domestic | Incandescent Lamps – Energy savings achievable. Reduction in brightness. |
| Lighting – Domestic | Compact Fluorescent – No energy saving as these draw a constant power. |
| Lighting – Commercial | HF electronic ballasts – No energy saving as these draw a constant power. |
| Lighting – Commercial | Magnetic ballasts – Very good savings achieved. |
| Lighting – Industrial | SON SONT SOX lamps – Energy savings are achievable. |
| Motors – Fixed Speed | Savings achieved on lightly loaded and oversized motors |
| Motors – Variable Speed | No savings achieved as constant power is drawn. |
| Equipment – Heating elements | Reduction of voltage will result in a reduction of heat output. |
| Equipment – Electronic Equipment | Equipment such as PC’s and laptops which operate via switch mode power supplies – No energy saving as these draw a constant power. |
Is there any effect on the equipment?
Voltage optimisation does have an effect on the output of some equipment. Incandescent lighting will have a lower light output when supplied from a lower voltage and equipment with electric heating elements will have a reduction in heat produced.
CIBSE do not recommend the use of voltage optimisation with high frequency electronic ballasts in lighting.
Is voltage optimisation suitable for my site?
To determine if Voltage Optimisation is suitable for a building a full assessment of the connected electrical load should be undertaken. It should be confirmed what percentage of the existing load is taken up by equipment for which voltage optimisation would be beneficial and ensure that no equipment that would have an adverse effect from a lower voltage will be effected.
The main areas where voltage optimisation is effective are lighting with magnetic ballasts, street or carpark lighting, and lightly loaded fixed speed motors. If your property contains a significant amount of such then energy savings can potentially be achieved by the installation of voltage optimisation.
As voltage optimisation is most effective when serving older, less energy efficient technology the cost of installation should be compared with the cost of upgrading the fittings or equipment as any savings from voltage optimisation will become obsolete with the upgrade to newer technology. This also needs to be considered when calculating the payback period of the installation.
For more information on VO contact Amanda Lewin at Parker Wilson Sustain LLP.